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Experimental methodology for assessing the environmental fate of organic chemicals in polymer matrices using column leaching studies and OECD 308 water/sediment systems: Application to tire and road wear particles
Abstract
Automobile tires require functional rubber additives including curing agents and antioxidants, which are potentially environmentally available from tire and road wear particles (TRWP) deposited in soil and sediment. A novel methodology was employed to evaluate the environmental fate of three commonly-used tire chemicals (N-cyclohexylbenzothiazole-2-sulfenamide (CBS), N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine (6-PPD) and 1,3-diphenylguanidine (DPG)), using a road simulator, an artificial weathering chamber, column leaching tests, and OECD 308 sediment/water incubator studies. Environmental release factors were quantified for curing (fC), tire wear (fW), terrestrial weathering (fS), leaching from TRWP (fL), and environmental availability from TRWP (fA) by liquid chromatography-tandem mass spectroscopy (LC/MS/MS) analyses. Cumulative fractions representing total environmental availability (FT) and release to water (FR) were calculated for the tire chemicals and 13 transformation products. FT for CBS, DPG and 6-PPD inclusive of transformation products for an accelerated terrestrial aging time in soil of 0.1years was 0.08, 0.1, and 0.06, respectively (equivalent to 6 to 10% of formulated mass). In contrast, a wider range of 5.5×10(-4) (6-PPD) to 0.06 (CBS) was observed for FR at an accelerated age of 0.1years, reflecting the importance of hydrophobicity and solubility for determining the release to the water phase. Significant differences (p<0.05) in the weathering factor, fS, were observed when chemicals were categorized by boiling point or hydrolysis rate constant. A significant difference in the leaching factor, fL, and environmental availability factor, fA, was also observed when chemicals were categorized by log Kow. Our methodology should be useful for lifecycle analysis of other functional polymer chemicals.
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... Such processes increase the complexity of the chemical composition of TRWP and make their global environmental study challenging. Moreover, most of the few studies on TRWP environmental fate focus on one of its individual component or family: for example, abiotic oxidative transformation of some additives (N-(1,3-dimethylbutyl)-N′-phenyl-pphenylenediamine (6PPD), diphenylguanidine (DPG), n-cyclohexyl-2benzothiazole-sulfenamide (CBS) (Hu et al., 2022;Seiwert et al., 2022;Tian et al., 2021;Unice et al., 2015) or tire elastomers . ...
... To date, the characterization of the elastomer in tire particles themselves is poorly documented and only addressed in a few studies dealing with the ecotoxicological impact of TRWP (Halle et al., 2020;Khan et al., 2019). The chemical composition of TRWP was mainly elucidated through the analysis of their leachates by LC-ESI-HRMS (Halsband et al., 2020;Thomas et al., 2023;Unice et al., 2015). Recently, Müller et al. (2022) combined non-target and suspect screening strategies to analyze extracts of different pieces of tire treads. ...
... They detected 214 organic substances of which more than one hundred leachates as potential water pollutants. Recent research works mainly focused on the detection and transformation of tire additives such as protective and vulcanizing agents or plasticizers (Halsband et al., 2020;Müller et al., 2022;Selbes et al., 2015;Unice et al., 2015;Zahn et al., 2019). Although SBR and IR are widely used markers for the detection and quantification of TRWP in the environment by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) (Goßmann et al., 2021;Miller et al., 2022aMiller et al., , 2022bRauert et al., 2022aRauert et al., , 2022bUnice et al., 2013Unice et al., , 2012, the elastomer part of tire, is relatively poorly characterized in TRWP transformation studies. ...
Roadway particles (RP) that can be collected with on-vehicle system, consist of a mixture of Tire and road wear particles (TRWP) with other traffic-derived particles (exhaust or non-exhaust) and/or biogenic compounds and represent a significant source of xenobiotics, susceptible to reach the different environmental compartments. The study of the RP fate is thus a major challenge to tackle in order to understand their degradation and impact. They offer a variety of carbon sources potentially usable by microorganisms, ranging from the tire-derived plasticizers, vulcanizing agents, protective agents and their transformation products, to other traffic, road and environmental-derived contaminants. A multi-analytical approach was implemented to characterize RP and study their biodegradation. Kinetics of RP extractions were monitored during 21 days in water, methanol, acetone and chloroform to identify leaching and extractable compounds and monitor the particle composition. The results confirmed that hundreds of readily leachable chemicals can be extracted from RP directly into water according to a dynamic process with time while additional poorly soluble compounds remain in the particles. Mass spectrometry (LC-HRMS and GC-MS) allowed us to propose 296 putative compounds using an extensive rubber database. The capacity of 6 bacterial strains, belonging to Rhodococcus, Pseudomonas and Streptomyces genera, to biodegrade RP was then evaluated over 14 days of incubation. The selected strains were able to grow on RP using various substrates. Elastomer monitoring by 1H NMR revealed a significant 12 % decrease of the extractable SBR fraction when the particles were incubated with Rhodococcus ruber. After incubation, the biodegradation of 171 compounds among leachable and extractable compounds was evaluated. Fatty acids and alkanes from rubber plasticizers and paraffin waxes were the most degraded putative compounds by the six strains tested, reaching 75 % of biodegradation for some of them.
... The leaching of chemicals from tire particles can be influenced by biotic (biodegradation) and abiotic (e.g., oxidation, mechanical degradation) factors (Wagner et al., 2022). Photodegradation studies on TWP have been performed to investigate the influence of photoaging on both particles and related chemicals (Unice et al., 2015;Fohet et al., 2023). These studies were, however, performed in dry conditions and dedicated studies simulating marine environmental conditions have not been published, yet. ...
... It is not clear, if these 23 TPs were formed directly from DPG, or if they were formed from DPG related transformation products already present in the tire material. It has been shown that only 50% of the initial amount of DPG in a starting material may remain unaltered after rubber curing (Unice et al., 2015). Artificial sunlight strongly supported the formation of these TPs, as they were hardly detectable under dark conditions (Figures 3A, B). ...
... Among the antioxidant compounds detected, 4hydroxydiphenylamine (4-HDPA), a hydrolysis product of 6-PPD (Unice et al., 2015), was most abundant, with higher amounts released from CMTT than from VCR and WCR (Supplementary Figure S1). Since 6-PPD and diphenylamine react rapidly with reactive oxygen species and as 4-HDPA is also reactive (Seiwert et al., 2022), the 4-HDPA concentrations in the CMTT leachates under sunlight exposure were extremely low, with near-zero concentration values during the whole experiment. ...
Tire wear particles (TWPs) represent one of the major anthropogenic pools of particles ending up in the environment. They contain a large variety of chemicals, a part of which may be released into the environment through leaching, although the influence of sunlight and other environmental factors during this process is still unclear. This laboratory study compares the leaching of organic compounds from TWP in seawater in the dark and under artificial sunlight for 1) cryo-milled tire tread (CMTT), 2) ‘virgin’ crumb rubber (VCR) and 3) crumb rubber immersed in the sea for ≥12 months prior to the experiments (WCR). Leachates were analyzed for dissolved organic carbon (DOC) and 19 tire-derived chemicals, benzothiazoles and phenylguanidines as well as phenylendiamines by liquid chromatography-high resolution-mass spectrometry. For DOC and most chemicals, the amounts released decreased in the order CMTT > VCR > WCR and increased when leaching occurred under artificial sunlight. sunlight also led to the formation of 23 transformation processes related to 1,3-diphenylguanidine (DPG). In contrast, 4-hydroxydiphenylamine (4-HDPA) and N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine quinone (6-PPDQ) were found in lower amounts upon sunlight exposure. The 19 quantified chemicals, however, did only account for 6%–55% of the DOC in the leachates; most of the DOC, thus, remained unexplained. This study highlights that the amount of chemicals leached from tire particles depends upon their aging history and may be modulated by environmental conditions.
... 6PPD was reported in tire and road wear particles (TRWPs) at 1000 ± 630 μg/g TRWP. 61 Assuming equal mass of the tread polymer and road encrustations in TRWPs, 62 6PPD concentrations in our TWP mixture are quite similar to those reported for the TRWP tread polymer (∼2000 ± 1260 μg/g TRWP tread polymer). All targeted TPs (level 1 TPs, TP 282b, and TP 274) were detected in pre-ozonation TWPs except 4s DPA (Table 1), likely reflecting used tire compositions and/or TP generation during TWP storage. ...
... The equivalent concentrations reported for tread polymer (4-HDPA, 84 ± 66 μg/g TRWP tread polymer; 4-ADPA, 34 ± 50 μg/g TRWP tread polymer) were ∼2-fold higher than those in our TWP mixture. 61 Different tire formulations or extraction methods (Soxhlet versus sonication) also may explain such compositional differences. ...
... All targeted TPs were detected in TWP leachate. Compared with TWP extracts, the contributions of 1,3-DMBA (25 ± 3 μg/g TWP; 72% contribution) and 4-HDPA (7.0 ± 0.7 μg/g TWP; 21% contribution) to ΣTPs further increased, followed by 5% contribution from 6PPDQ (1.6 ± 0.03 μg/g TWP) and <1% contribution from 4-ADPA, 4s DPA, and 4-NDPA (Table 1, Figure 4) M phosphate buffer in Klockner et al.) for leaching (compared to DI water here) and did not employ sample enrichment (versus 200-fold SPE extraction here), 36,61 which may result in reduced leaching potentials for cationic TPs, higher LODs, or ion suppression during mass spectrometry. Also, Klockner et al. used syringe filtration (0.45 μm cellulose acetate) to separate TWPs from solution, which may result in sorptive losses of 6PPDQ and other TPs to filter materials. ...
6PPD, a tire rubber antioxidant, poses substantial ecological risks because it can form a highly toxic quinone transformation product (TP), 6PPD-quinone (6PPDQ), during exposure to gas-phase ozone. Important data gaps exist regarding the structures, reaction mechanisms, and environmental occurrence of TPs from 6PPD ozonation. To address these data gaps, gas-phase ozonation of 6PPD was conducted over 24-168 h and ozonation TPs were characterized using high-resolution mass spectrometry. The probable structures were proposed for 23 TPs with 5 subsequently standard-verified. Consistent with prior findings, 6PPDQ (C18H22N2O2) was one of the major TPs in 6PPD ozonation (∼1 to 19% yield). Notably, 6PPDQ was not observed during ozonation of 6QDI (N-(1,3-dimethylbutyl)-N'-phenyl-p-quinonediimine), indicating that 6PPDQ formation does not proceed through 6QDI or associated 6QDI TPs. Other major 6PPD TPs included multiple C18H22N2O and C18H22N2O2 isomers, with presumptive N-oxide, N,N'-dioxide, and orthoquinone structures. Standard-verified TPs were quantified in roadway-impacted environmental samples, with total concentrations of 130 ± 3.2 μg/g in methanol extracts of tire tread wear particles (TWPs), 34 ± 4 μg/g-TWP in aqueous TWP leachates, 2700 ± 1500 ng/L in roadway runoff, and 1900 ± 1200 ng/L in roadway-impacted creeks. These data demonstrate that 6PPD TPs are likely an important and ubiquitous class of contaminants in roadway-impacted environments.
... Complementing decades of investigation of conventional water pollutants such as nutrients, salts, and trace heavy metals, [1][2][3][4][5][6][7] various synthetic organic contaminants are now receiving more research attention in roadway systems. [8][9][10][11][12][13][14][15] Recently, 6PPDquinone (2-((4-methylpentan-2-yl)amino)-5-(phenylamino) cyclohexa-2,5-diene-1,4-dione) or "6PPDQ", a tire rubber derived compound that can induce acute toxicity to coho salmon (Oncorhynchus kisutch), was reported globally in atmospheric particulate matter, dusts, soils, runoff, surface waters and even human urine. [16][17][18][19][20][21][22][23] 6PPDQ is a transformation product of the common antioxidant 6PPD (N-(1,3-dimethylbutyl)-N ′phenyl-p-phenylenediamine) that is ubiquitously used in tire rubber products (0.4-2% by mass). ...
... Leachates were collected at 0.25, 0.5, 1, 1.5, 2, 3, 4, 5, and 6 h (Fig. S1). † Preliminary tests (15,45, and 90 mL min −1 ) determined optimal ow rates without apparent advective limitations. These tests were conducted in triplicate with identical TWP masses and leaching times. ...
... If roadway residual TRWPs consist of 50% tire rubber, 280 000-690 000 metric tons of TWPs per year are deposited to the road and available for localized leaching. Using measurements from this study, 7.14 ± 1.3 (by the aqueous leaching model) to 15 59 and assuming a runoff coefficient of 0.85, 60 we estimate an average roadway runoff volume of 3.44 × 10 13 L per year on U.S. roadways. Using these estimates, average 6PPDQ concentrations in roadway runoff would range from 60-310 ng L −1 . ...
We here report chemical characteristics relevant to the fate and transport of the recently discovered environmental toxicant 6PPD-quinone (2-((4-methylpentan-2-yl)amino)-5-(phenylamino)cyclohexa-2,5-diene-1,4-dione or "6PPDQ"). 6PPDQ is a transformation product of the tire rubber antioxidant 6PPD that is ubiquitous in roadway environments, including atmospheric particulate matter, soils, runoff, and receiving waters, after dispersal from tire rubber use and wear on roadways. The aqueous solubility and octanol-water partitioning coefficient (i.e. log KOW) for 6PPDQ were measured to be 38 ± 10 μg L-1 and 4.30 ± 0.02, respectively. Within the context of analytical measurement and laboratory processing, sorption to various laboratory materials was evaluated, indicating that glass was largely inert but loss of 6PPDQ to other materials was common. Aqueous leaching simulations from tire tread wear particles (TWPs) indicated short term release of ∼5.2 μg 6PPDQ per gram TWP over 6 h under flow-through conditions. Aqueous stability tests observed a slight-to-moderate loss of 6PPDQ over 47 days (26 ± 3% loss) for pH 5, 7 and 9. These measured physicochemical properties suggest that 6PPDQ is generally poorly soluble but fairly stable over short time periods in simple aqueous systems. 6PPDQ can also leach readily from TWPs for subsequent environmental transport, posing high potential for adverse effects in local aquatic environments.
... The discovery of this molecule raises concerns about the potential toxicity of tire leachates, especially due to the degradation products that could have different toxicity and persistence than the parent molecule. In this context, leaching studies from TRWP or tire cryogrinds have been receiving growing attention and have focused on various substances, including heavy metals and organic additives (Wagner et al., 2022;Müller et al., 2022;Seiwert et al., 2022;Unice et al., 2015;Thomas et al., 2022;Klöckner et al., 2021). Collection and analysis of environmental samples also revealed the occurrence of several PPD-derived quinones in urban runoff, roadside soils, and air particles (Cao et al., 2022). ...
... The remaining elastomer fraction was quantified over time by pyrolysis-gas chromatography, and the authors estimated a half-life of the polymer in soil of 16 months, with a significant abiotic contribution. Klöckner et al.(Klöckner et al., 2021) investigated the accelerated degradation of additives in tire particles after 72 h of aging under UV light and 20-day aging at 80°C, while Unice et al. (Unice et al., 2015) and Thomas et al.(Thomas et al., 2022) proposed artificial UV light aging of 1 month equivalent to natural aging of 1 year. Klockner et al. (Klöckner et al., 2021) have identified three potential organic markers to evaluate the presence of TRWP in sediment and soil (i.e., 6-PPD-quinone, N-formyl-6-PPD and hydroxylated N-1,3-dimethylbutyl-N-phenyl quinone diimine). ...
... The ratio 6QDI/6PPD remains approximately constant during accelerated aging experiments. A similar behavior was observed with Component 185 (Unice et al., 2015;Lattimer et al., 1983), although with slower dissipation rates by a factor of ca. 2 compared to 6PPD or 6QDI. The transformation from 6PPD to 6QDI involves a radical reaction followed by rearrangements, while the transformation from 6PPD to supposedly 4-ADPA (Component 185) involves the loss of the alkyl chain that leads to the formation of a primary amine. ...
Tire and road wear particles (TRWP) are polymer-based microparticles that are emitted into the environment during tire usage. Growing efforts are currently being made to quantify these emissions, characterize the leachates and assess their environmental impact. This study aimed to investigate the effect of aging on TRWP composition. Cryomilled tire tread particles (CMTTP) and TRWP were exposed for different durations to three aging conditions: accelerated thermal and photochemical aging and natural outdoor aging. Particles were then extracted with cyclohexane/ethanol. The time-concentration profiles of 23 additives and transformation products present in these extracts were determined by UHPLC-HRMS. Several chemicals, such as N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6-PPD) or 1,3-diphenylguanidine (DPG), decayed exponentially under all aging conditions, with half-lives of a few days under artificial photoaging versus dozens of days under pure thermal aging at 60 °C. The natural aging profiles lie between those 2 laboratory aging conditions. Other chemicals, such as 6PPD-quinone, presented bell-shaped concentration profiles within CMTTP when particles were exposed to UV light. 6PPD-quinone reached a maximal concentration within a month under natural aging. For TRWP, the initial load of 6PPD-quinone had already reached a maximum prior to the aging experiments and decreased exponentially under natural aging with a half-life below one month. Pure thermal aging induced a significantly slower decay of 6PPD-quinone within TRWP (half-life of half a year), emphasizing a greater stability and persistence in environmental compartments without light. This study highlighted that the more readily accessible CMTTP could be considered a reasonable proxy of TRWP to investigate the fate of chemicals within rubber particles, at least from a qualitative standpoint. Overall, the concentrations of 20 of the evaluated chemicals decreased by >50 % within 50 days under natural aging.
... TRWP research on terrestrial soil systems has been scarce but has recently emerged as a key area (Dierkes et al., 2019;Huang et al., 2020;Hurley et al., 2018;Klöckner et al., 2021a;Piehl et al., 2018;Rogge et al., 2012;Unice et al., 2019). TRWP has been detected as a parent compound, as transformation products or as leachates of tire constituents of TRWP in soils (Marwood et al., 2011;Unice et al., 2015). Thus, there is a need to quantify TRWP present in the environment to understand its adverse effects. ...
... Tire tread contains elastomers like natural rubber (NR) and styrenebutadiene-rubber (SBR) as the major component in combination with additives to act as curing accelerator, anti-oxidants, fillers, etc. (Rauert et al., 2021). Pyrolysis-based analytical techniques are commonly used for the quantification of TRWP in soil systems (Goβmann et al., 2021;Haydary et al., 2012;ISO/TS 21396, 2017;Nuelle et al., 2014) in addition to LC-MS (Klöckner et al., 2021a;Salas et al., 2016;Unice et al., 2015) and thermal extraction desorption gas chromatography . . Using such techniques, TRWP concentrations ranging from 800 to 4500 μg/g sediment dry weight to 10,000 μg TRWP/g sediment dry weight have been reported (Marwood et al., 2011;Panko et al., 2013a;Unice et al., 2013). ...
... Pyrolysis-GC-MS uses very small amount of sample and is challenging due to heterogeneous mature of road dust and soil samples. TRWP quantification markers reported include: benzothiazole (Asheim et al., 2019;Avagyan et al., 2013;Gągol et al., 2015;Pan et al., 2012;Wagner et al., 2018), para-phenylenediamines (Klöckner et al., 2021a(Klöckner et al., , 2021bUnice et al., 2015), diphenylguanidine (Challis et al., 2021;Johannessen et al., 2021;Unice et al., 2015) oleamides (Chae et al., 2021), and hexamethoxymethylmelamine (Johannessen et al., 2021). In the present work, the main objective was the TRWP analysis and quantification using non-pyrolysis method. ...
Tire and road wear particles (TRWP) are becoming an important research question with potential risks on ecological system. A comprehensive understanding of their detection and quantification in soils are challenged by the inherent technological inconsistencies, lack of well-set standardized methods, and generalized protocols. Reference tire cryogrinds were subjected to abiotic weathering. Next, the total environmental availability from parent elastomers and the release of additives from tire tread compounds were evaluated using mass concentration factors obtained from abiotic weathered tire cryogrinds. Headspace Gas chromatography-mass spectroscopy (HS-GC-MS) was employed as a nontargeted, suspect screening analysis technique to identify the tire related intermediates. Benzothiazole, 1,2-dihydro-2,2,4-trimethylquinoline (TMQ), aniline, phenol and benzoic acid were detected as tire tetrahydrofuran leachates. Total environmental availability of TMQ and benzothiazole were in the range of 1.7 × 10⁻³ and 0.11, respectively. Benzene and benzoic acid derivatives were identified as marker compounds for environmental samples. A TRWP content evaluation was made possible by quantifying marker concentrations and reference tire cryogrind formulation. TRWP content in the size range of 1–5 mm was between 800 and 1300 μg/g and 1200–3100 μg/g TRWP in Ohio and Kansas soil. For TRWP less than 1 mm, 0.15–2.1 wt% content was observed in Kansas and Ohio samples and were seemingly dependent on the locations and the traffic. This simple, widely applicable quantification method for TRWP analysis provides a database of tire degradation and TRWP intermediates. The TRWP content research is critical for further TRWP research development in terrestrial environment.
... The discovery of this molecule arises concerns about the potential toxicity of tire leachates, especially due to the degradation products that could have different toxicity and persistence than the parent molecule. In this context, leaching studies from TRWP or tire cryogrinds have been receiving growing attention and focused on various substances including heavy metals and organic additives 17,25,26,[32][33][34] . Collection and analysis of environmental samples also revealed the occurrence of several PPD-derived quinones in urban runoff, roadside soils, and air particles 14 . ...
... P r e p r i n t n o t p e e r r e v i e w e d 4 pyrolysis-gas-chromatography and the authors estimated a half-life of the polymer in soil of 16 months, with a significant abiotic contribution. Klöckner et al. 34 investigated the accelerated degradation of additives in tire particles after 72 hours of aging under UV light and 20-day aging at 80°C while Unice et al. 32 and Thomas et al. 33 proposed artificial UV light aging of 1 month equivalent to natural aging of 1 year. Klockner et al. 34 have identified three potential organic markers to evaluate the presence of TRWP in sediment and soil (i.e. ...
... The ratio 6QDI/6PPD remains approximately constant during accelerated aging experiments. A similar behavior was observed with component 185 32,36 , though with slower dissipation rates by a factor ca. 2 compared to 6PPD or 6QDI. The transformation from 6PPD to 6QDI involves a radical reaction followed by rearrangements, while the transformation from 6PPD to supposedly 4-ADPA (component 185) involves the loss of the alkyl chain that leads to the formation of a primary amine. ...
... Likely transformation products of DPG have been tentatively identified by Seiwert et al. (2020) in water samples, but their structures have not yet been proposed . However, the compound aniline is also known to be a common transformation product of DPG (Peter et al., 2018;Unice et al., 2015;Willoughby, 2003). DPG has also been found to react rapidly with chlorine and bromine during waste treatment processes, forming a variety of transformation products as outlined by Sieira et al. (2020). ...
... However, 6PPD-quinone is not the sole transformation product of 6PPD. Various transformation products of 6PPD have been identified in TWPs (Klöckner et al., 2021a) After artificial aging (ambient heat, UV light, and moisture) of TWPs, four transformation products of 6PPD were detected including 4-aminodiphenylamine (4-ADPA), 4-nitrodiphenylamine (4-NDPA), 4-hydroxydiphenylamine (4-HDPA), and DPA, the latter of which is expected to have higher volatility than the others (Unice et al., 2015). Additional transformation products, produced from 6PPD reacting with ozone, have also been identified and merit investigation in terms of their atmospheric occurrence and fate (Lattimer et al., 1983;Seiwert et al., 2022;Tian et al., 2020). ...
... Overall, 31 unique TPs have been identified. Of these TPs, six were identified by Borowska et al. (2016) under UV and UV/H 2 O 2 systems with a mercury lamp, twelve were identified by Bertoldi et al. (2020) under direct photolysis in aqueous solution under either natural sunlight or a high pressure mercury lamp, three were identified by Unice et al. (2015) under artificial aging conditions (ambient heat, UV light, and moisture), and 21 were identified by Catallo and Junk (2005) in sediment. There was considerable overlap of the identified transformation products between studies (Fig. 8). ...
Pollution derived from car tires is of growing research interest due to its apparent omnipresence in the urban environment and its associated toxicity. Studies have focused largely on the occurrence of these tire materials, deemed tire wear particles (TWPs), and their associated chemicals in the aquatic environment. However, less attention has been paid to atmospheric TWPs, which can remain airborne and be transported over long distances. In addition, there are few studies pertaining to the gaseous contaminants originating from tire wear, creating a significant knowledge gap. This review aims to summarize the current state of knowledge surrounding atmospheric tire wear pollution by detailing relevant studies conducted under both laboratory and ambient environmental conditions. Organic chemicals that are associated with this form of pollution, including diphenylamine antioxidants, phthalates, benzothiazole, benzotriazoles, and alkylphenols were highlighted for their potential implications for air. While a number of studies have investigated oxidation in aquatic environments, the current review highlights a clear absence of oxidation product information relevant to air. There is also a critical research gap surrounding the physico-chemical properties of these potential atmospheric pollutants. As a result, the environmental behaviour and fate of these contaminants are largely unknown. Based on these knowledge gaps, we propse recommendations for future work to advance this area of research.
... DPG was the substance with the highest intensity in leachates and is primarily used as vulcanisation accelerator during tire production (Baumann and Ismeier, 1998;Peter et al., 2018;Seiwert et al., 2020;Unice et al., 2015). In a nontarget screening study DPG was clearly associated to road run-off (Du et al., 2020) and can thus be categorized as tire-specific water contaminant. ...
... Tire-linked decomposition products found in all nine tire leachates were 4-hydroxydiphenylamine (decomposition product of 6-PPD), benzothiazole (decomposition product of sulfenamides) and caprolactam. While these decomposition products have a clear linkage to rubber tires (Baumann and Ismeier, 1998;Seiwert et al., 2020;Unice et al., 2015) they are not tire-specific. However, it should be noted that benzothiazole and caprolactam have been widely detected in ground or drinking water (Schriks et al., 2010;Schulze et al., 2019). ...
... The log D at pH 7.4 and the intensity share in the water extracts (fraction of total intensity found within water extracts) are given as well. Vulcanisation accelerator (Baumann and Ismeier, 1998;Peter et al., 2018;Seiwert et al., 2020;Unice et al., 2015) C 13 H 13 N 3 1.28 9/9 68% ε-Caprolactam (105-60-2) Decomposition product (Baumann and Ismeier, 1998;Seiwert et al., 2020) C 6 H 11 NO 0.31 9/9 100% Benzothiazole (95-16-9) ...
Tire wear particles are not only the type of polymer particles most prevalent in the environment but also act as source of various organic micropollutants, many of which are likely still unknown. We extracted particles prepared from nine tires in artificial freshwater (28 d) with the goal to characterize leachables (max intensity >10⁵ in artificial freshwater), which are tire-borne water contaminants. A subsequent extraction of these particles with acetone (3 h) was used to assess the long-term leaching potential. A suspect and nontarget screening in aliquots of each extract led to the detection of 214 organic substances of which 145 were classified as leachables. The intrinsic polarity of some leachables (mean log D (pH 7.4) 3.9), which facilitates an increased aquatic mobility, highlights their potential as environmental water contaminants. With N,N′-diphenylguanidine (DPG) and benzothiazole, two of the ten unequivocally identified leachables, are classified as potential persistent, mobile and toxic substance by the German Environment Agency. Of the identified chemicals DPG showed the highest intensities in aqueous extracts and N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6-PPD), the precursor of 6-PPD-quinone, in acetone extracts. A comparison between the 69 detected suspects and 174 high-intensity signals (>10⁶) detected in the nontarget screening led to an overlap of only 29 features. A detailed investigation of the remaining high-intensity suspects revealed the presence of 13 proposed DPG reaction products, further highlighting the chemical complexity of tires. Consequently, we conclude that there are many, often still unrecognized chemicals entering the aquatic environment through leaching from tire wear particles.
... These additives and their transformation products, i.e., tire-derived compounds, are not chemically bound within the rubber matrix, and many leach into the environment. Some of the main chemical additives are vulcanization accelerators including benzothiazoles, and several guanidine derivatives such as 1,3-diphenylguanidine (DPG), which comprise 0.5% of tire mass each (Unice et al., 2015), corrosion inhibiting benzotriazoles, the crosslinking agent hexa (methoxymethyl) melamine (HMMM), and p-phenylenediamine compounds (PPDs), which are used as antiozonants, and represent 0.8% of tire mass (Unice et al., 2015). These tire-derived compounds are ubiquitously detected in the environment. ...
... These additives and their transformation products, i.e., tire-derived compounds, are not chemically bound within the rubber matrix, and many leach into the environment. Some of the main chemical additives are vulcanization accelerators including benzothiazoles, and several guanidine derivatives such as 1,3-diphenylguanidine (DPG), which comprise 0.5% of tire mass each (Unice et al., 2015), corrosion inhibiting benzotriazoles, the crosslinking agent hexa (methoxymethyl) melamine (HMMM), and p-phenylenediamine compounds (PPDs), which are used as antiozonants, and represent 0.8% of tire mass (Unice et al., 2015). These tire-derived compounds are ubiquitously detected in the environment. ...
Introduction
Tire and road wear particles are one of the most abundant types of microplastic entering the environment. The toxicity of tire and road wear particles has been linked to their organic additives and associated transformation products. Tire and road wear particles, and associated tire-derived compounds are introduced to the agricultural environment via atmospheric deposition, irrigation with reclaimed wastewater, and the use of biosolids (treated sewage sludge) as fertilizer. In the agricultural environment, these tire-derived compounds could be taken up by edible plants, leading to human exposure.
Methods
Sixteen tire-derived compounds were measured in twenty-eight commercial leafy vegetable samples from four countries. Based on the results, the estimated daily intake of these tire-derived compounds was calculated due to leafy vegetable consumption based on local diets under a mean and maximum concentration scenario.
Results
In commercial leafy vegetables, six tire-derived compounds were detected: benzothiazole (maximum concentration—238 ng/g dry weight), 2-hydroxybenzothiazole (maximum concentration—665 ng/g dry weight), 1,3-diphenylguanidine (maximum concentration—2.1 ng/g dry weight), N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD, maximum concentration—0.4 ng/g dry weight), N-Isopropyl-N-phenyl-4-phenylenediamine (IPPD, maximum concentration—0.1 ng/g dry weight), and N-phenyl-N-cyclohexyl-p-phenylenediamine (CPPD, maximum concentration—0.3 ng/g dry weight). At least one compound was present in 71% of samples analyzed. The estimated daily intake for 1,3-diphenylguanidine ranged from 0.05 ng/person/day in the mean scenario to 4.0 ng/person/day in the maximum scenario; benzothiazole ranged from 12 to 1,296 ng/person/day; 6PPD ranged from 0.06 to 2.6 ng/person/day; IPPD ranged from 0.04 to 1.1 ng/person/day; CPPD ranged from 0.05 to 2.6 ng/person/day.
Discussion
Statistical analyses did not reveal correlation between known growth conditions and tire-derived compound concentrations in the leafy vegetable samples. The estimated daily intake via leafy vegetable consumption was generally lower than or comparable to the estimated daily intake via other known sources. However, we show that tire-derived compounds are taken up by foodstuff, and exposure might be higher for other produce. Future studies are needed to uncover pathways of tire-derived compounds from road to food, assess the exposure to transformation products, and investigate the biological effects associated with this exposure.
... Transfer of experimental data generated from CMTT to TRWP may not be an easy task (Fohet et al., 2023). Two previous studies have studied the alteration of chemicals in TRWP by artifical aging: Unice et al. (2015) investigated 6-PPD, DPG, CBS and some of their transformation products and Fohet et al. (2023) studied the transformation of DPG, benzothiazole (BT), TMQ, 6-PPD and 6-PPDQ. ...
... Fresh CMTT is dominated by parent compounds (6-PPD, CBS, MBT, DPG). However, the chemical composition is more complex than visible from this quantitative study, as TPs formed during production are not well known, yet (Unice et al., 2015). As long as the known parent chemicals are available, the early TPs formed from them may be of relevance with their concentration determined by the rate of their ongoing formation and further transformation. ...
Tire and road wear particles (TRWP) are generated in large quantity by automobile traffic on roads but their way of degradation in the environment is largely unclear. Laboratory experiments were performed on the effect of elevated temperature (simulating 2–3 years), sunlight exposure (simulating 0.5 years) and mechanical stress on the physical properties and chemical composition of TRWP and of cryo-milled tire tread (CMTT). No significant effects were observed of the applied mechanical stress on mean properties of pristine particles. After sunlight exposure up to 40 % in mass were lost from the TRWP, likely due to the loss of mineral incrustations from their surface. The chemical composition of TRWP and CMTT was characterized by determining 27 compounds, antioxidants (phenylene diamines), vulcanization agents (benzothiazoles and guanidines) and their transformation products (TPs). Extractables of TRWP (580–850 μg/g) were dominated by TPs, namely benzothiazolesulfonic acid (BTSA). CMTT showed much higher amounts of extractables (4600 μg/g) which were dominated by parent chemicals such as N-(1,3-dimethylbutyl)-N′-phenyl-1,4-phenylenediamine (6-PPD), diphenylguanidine (DPG) and mercaptobenzothiazole (MBT). Sunlight exposure affected the amount of extractables more strongly than elevated temperature, for TRWP (−45 % vs −20 %) and CMTT (−80 % vs −25 %) and provoked a clear shift from parent compounds to their TPs. After sunlight exposure extractables of TRWP were dominated by BTSA and DPG. Sunlight exposure drastically reduced the 6-PPD amount extracted from both, TRWP and CMTT (−93 %, −98 %), while its quinone (6-PPDQ) increased by around 1 % of the 6-PPD decrease, only. For many TPs, concentration in leachates were higher than in extracts, indicating ongoing transformation of their parent compounds during leaching. These results highlight that abiotic aging of TRWP leads to strong changes in their chemical composition which affect their particle properties and are of relevance for the environmental exposure to tire-related chemicals.
... Among many other compounds, 2-mercaptobenzothiazole (MBT) and 1,3-diphenylguanidine (DPG) are intensively used as vulcanization agents; they can represent up to 0.5% of the tire rubber. 9 Phenylenediamine compounds, such as N-(1,3dimethylbutyl)-N′-phenyl-1,4-phenylenediamine (6PPD), are also commonly used as antioxidants and antiozonants (about 0.9% of the tire tread) in the final product to prevent cracking and degradation of the rubber during wear. 10 Highly aromatic oils used in rubber manufacturing commonly include polycyclic aromatic hydrocarbons (PAHs), some of which are classified as carcinogenic. ...
... An alternative explanation could be that ANI was formed due to degradation of DPG. 9 In SF intestinal , all compounds were rapidly solubilized during the in vitro digestion time of 24 h. All solubilization kinetics were best fitted by a logarithmic model except for DPG for which the solubilization was best fitted by a diffusioncontrolled model (Figure 1b). ...
Tire and road wear particles (TRWP) account for an important part of the polymer particles released into the environment. There are scientific knowledge gaps as to the potential bioaccessibility of chemicals associated with TRWP to aquatic organisms. This study investigated the solubilization and bioaccessibility of seven of the most widely used tire-associated organic chemicals and four of their degradation products from cryogenically milled tire tread (CMTT) into fish digestive fluids using an in vitro digestion model based on Oncorhynchus mykiss. Our results showed that 0.06-44.1% of the selected compounds were rapidly solubilized into simulated gastric and intestinal fluids within a typical gut transit time for fish (3 h in gastric and 24 h in intestinal fluids). The environmentally realistic scenario of coingestion of CMTT and fish prey was explored using ground Gammarus pulex. Coingestion caused compound-specific changes in solubilization, either increasing or decreasing the compounds' bioaccessibility in simulated gut fluids compared to CMTT alone. Our results emphasize that tire-associated compounds become accessible in a digestive milieu and should be studied further with respect to their bioaccumulation and toxicological effects upon passage of intestinal epithelial cells.
... Some of these compounds have been found to be harmful to organisms, such as hexa(methoxymethyl)melamine (HMMM), N-1,3-dimethylbutyl-N 0-phenyl-pphenylenediamine-quinone (6-PPD-quinone), benzothiazoles, aniline, 1,3diphenylguanidine (DPG) and different polycyclic aromatic hydrocarbons (PAHs) (Brinkmann et al., 2022;Halsband et al., 2020;Marwood et al., 2011;Peter et al., 2018;Seiwert et al., 2020;Tian et al., 2022;Tian et al., 2021;Unice et al., 2015). Both HMMM and 6-PPD-quinone have been related to acute toxicity and mass-deaths of salmon species (coho salmon Oncorhyncus kisutch, rainbow trout Oncorhynchus mykiss, brook trout Salvelinus fontinalis) in North America (Brinkmann et al., 2022;Peter et al., 2018;Tian et al., 2021), and following these initial studies, both compounds and their transformation products have been detected in various environmental compartments across different continents (Cao et al., 2022;Challis et al., 2021;Johannessen et al., 2022;Johannessen et al., 2021;Klöckner et al., 2021b;Rauert et al., 2022;Rauert et al., 2020;Seiwert et al., 2022). ...
... About 60% of the leachables were classified as mobile compounds, indicating a large potential for transport in the environment (Müller et al., 2022). Examples of tirederived chemicals that have been found to be harmful to organisms are benzothiazoles, N-1,3-dimethylbutyl-N 0-phenyl-p-phenylenediamine (6-PPD), 1,3-diphenylguanidine (DPG) and different polycyclic aromatic hydrocarbons (PAHs) Seiwert et al., 2020;Tian et al., 2021;Unice et al., 2015). ...
... 39,40 TRWPs have been detected in soil samples as a parent compound, as leachates, or as hydrolysis or transformation products of tire constituents. 22,41,42 TRWPs are quantified 19,20 by advanced sensitive analytical techniques and elastomerspecific pyrolysis markers. ISO 21396 provides a generalized method to determine TRWP mass concentration using pyrolysis-GC−MS 43 that has been validated by at least one study. ...
... Nontargeted GC−MS is also used to analyze TRWPs. 7,47 However, most of the literature assessed the environmental impact of the tire particles using column leaching tests, accelerated weathering tests, 41,48 extractions, and aerobic incubators. 13,49 Although these studies did not separate TRWPs from soil, they do provide a database of possible transformation products. ...
A comprehensive understanding of tire and road wear particles (TRWPs) and their detection and quantification in soils is still challenged by the lack of well-set standardized methods, inherent technological inconsistencies, and generalized protocols. Our protocol includes soil sampling, size separation, and organic matter removal by using hydrogen peroxide followed by density separation and analysis. In this context, roadside soil samples from different sites in Kansas and Ohio, USA, were collected and analyzed. Tire cryogrinds analogous to TRWPs were used to evaluate various density separation media, and collected particles more than 1 mm in size were then subjected to infrared spectroscopy (IR), thermogravimetric analysis (TGA), and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) to confirm TRWP presence. Particles smaller than 1 mm were Soxhlet extracted, followed by gas chromatography–mass spectrometry (GC–MS) to validate the presence of tire-related intermediates. SEM-EDX validated the presence of elemental combinations (S + Zn/Na) ± (Al, Ca, Mg, K, Si) attributed to tires. Ketones, carboxylic acids, epoxies, cyclohexane, and benzothiazole sulfenamide (BTS) intermediates were the most probable tire-related intermediates observed in the roadside soil samples. Thus, this simple, widely applicable, cost-effective sample preparation protocol for TRWP analysis can assist TRWP research advancement in terrestrial environments.
... In this study, additional moistening was used with distilled water. When TPs are soaked in the aquatic media, leaching patterns could be changed by their base leachate (Kalbe et al., 2013;Unice et al., 2015). TP exposure was the only consideration of toxicity in soil organisms as environmental water was not used as a moisture supply source. ...
... Generated TWP detected in the environmental media accounts for more than 60 % mineral composition of a particle with various minerals such as Si, Al, and Ca, while virgin TPs contain 46 % polymer with high contents of polycyclic aromatic hydrocarbon (Kreider et al., 2010). In addition, when the aging process continues, the emission of 6-PDD from TPs decreases (Unice et al., 2015). In the early stage of TPs, the rubber binding force becomes weak, resulting in rapid leaching of chemicals (Lu et al., 2021;Wagner et al., 2022), and this continuous leaching decreases the toxicity of chemical effects on living organisms. ...
Tire particles are generated by the abrasion of tire treads on roads and are major contributors to microplastics in soil environments. Contamination by tire wear particles worsens annually as the use of personal mobilities increases. Tire particles (112-541 µm) were obtained from three types of personal mobility tires (bicycle, car, and electric scooter) and exposed to plants (Vigna radiata) and springtails (Folsomia candida) for 28 d to assess the toxicity of each tire-particle type. The laboratory-generated tire particles exhibit adverse effects depending on the origin of the tire or test species. Particles from bicycle or electric-scooter tires changed the soil's bulk density and water holding capacity and adversely affected plant growth. Car tire particles had leached various organic compounds and induced detrimental effects on springtails (adult and offspring growth). We concluded that laboratory-generated tire particles (frow new tires) can affect the soil environment by changing soil properties and leaching chemicals; thus, causing adverse effects on soil organisms. Since this study found tire particle toxicity on soil organisms, it would be possible to compare the various contamination levels in areas near road soil and other clean soils.
... Our experiment was performed by deriving the TWP from a used car tyre, thus testing a specific material with a peculiar composition that can influence bacterial growth. Further research on the potential effect of tyres with a different composition in macro-(natural and synthetic rubber) and microelements (either in TWP from tyres of different brands but especially from car and truck tyres) could lead to a more precise definition of the importance of leaching and non-dissolvable organic matter proportions in determining the microbial community dynamics [61]. ...
... The limited increment in available MP surface detected with increasing the proportion of TWP does not seem to be a driver for the observed trends but, the larger shift in MPs mass (and thus, indirectly, in nutrients introduced to the system) could explain the described dynamics. In fact, not only reactive P decreases and TOC increases while higher TWP proportions are in the vessels, but also N presents interesting trends: the decrement in N-NO 3 is fully compensated by an increment in organic N. According to literature data, the ON leached from the TWP [61,65] can account for about 10% of those actually calculated for our system, while the predominant fraction is possibly derived from bacterial activity, specific for the different communities [66], and possibly concentrated within the biofilm on TWP. ...
Although abundant and chemically peculiar, tyre wear microplastic particles (TWP) and their impact on the microbial communities in water are largely understudied. We tested in laboratory based semi-continuous cultures the impact of TWP and of polyethylene terephthalate (PET) derived particles (following a gradient of relative abundance) on the pathobiome (the group of potential human pathogenic bacteria) of a freshwater microbial community exposed to contamination by the effluent of a urban wastewater treatment plant, for a period of 28 days. We could define the modulated impact of the two types of microplastic particles: while PET does not favour bacterial growth, it offers a refuge to several potential pathogens of allochthonous origin (from the treated sewage effluent), TWP act as an additional carbon source, promoting the development and the massive growth of a biofilm composed by fast-growing bacterial genera including species potentially harmful and competitive in abating biodiversity in surface waters. Our results demonstrate the different ecological role and impact on freshwater environments of TWP and PET particles, and the need to approach the study of this pollutant not as a whole, but considering the origin and the chemical composition of the different particles.
... Several previous studies concentrated on assessing the environmentalimpact potential using accelerated weathering tests, column leaching tests, extractions, and aerobic incubators [ 7 , 22 ]. For instance, Unice et al. [16] studied the fate of additives like benzothiazole, diphenyl guanidine and para phenylene diamine using column leaching experiments and provided a database for possible transformation products. Further, Eisentraut et al. [23] reported the effective use of thermal extraction desorption gas chromatography (TED-GC-MS) for identifying and quantifying TRWP. ...
... Thus, the UV-exposure testing that was conducted for 70 0, 10 0 0 and 2100 h, which was equivalent to 1, 1.5 and 3 years in natural environment, respectively. The acceleration factor yielded slightly longer exposure times than Unice et al. [16] who achieved 3 years aging after 1191 h, in a chamber equipped with 340 nm UVA UV light. Critical analysis of the infra-red spectral peak changes was evaluated as a sign of probable degradation of the tire cryogrind. ...
The abundance of microplastics found in the environment is a major cause of concern. Tire tread particles containing additives such as curing accelerators and antioxidants, can be a major source of elastomer pollution in the environment. Such tire particles combined with road pavement particles are referred to as tire and road wear particles, TRWP. The environmental availability from parent elastomers and the release of additives in the process of abiotic degradation were evaluated using freeze-thaw, wet-dry and accelerated UV-weathering experiments. Acceleration factor determination tests were conducted to correlate UV-exposure to the natural aging in the environment. Freeze-thaw testing showed many additives such as diphenyl guanidine (DPG), benzothiazole sulfenamide (BTS) and para-phenylene diamine (6 PPD) as tetrahydrofuran leachates and BTS transformation products. Further, UV exposure equivalent to 1.5 yr., 3 yr. and 5 yr. aging resulted in the formation a combination of ketones and carboxylic acids for styrene butadiene rubber (SBR), natural rubber (NR), and butadiene rubber-based tire cryogrinds. Attenuated total reflectance- Fourier- transform infrared spectroscopy (ATR-FTIR) was used to detect the degradation of the elastomers on UV-exposure while gas chromatography-mass spectroscopy (GC-MS) was used as a nontargeted, suspect screening analysis technique. The degradation intermediates and leachates identified using GC-MS represents useful data for the life cycle analysis of the functional polymers and additives and their possibility of environmental release.
... An estimated 50% of TWP deposited on roads are not washed off by precipitation. 48 Instead, they are an in situ source of water-soluble contaminants, including those with toxic properties like 6PPD-quinone, for at least several years. 48 As such, there is a need to evaluate the relative contribution of vehicle tires on-road vs worn tire particles, particles embedded in the road vs free, and particles leaching in situ vs mobilized with runoff to the load of tire-derived chemicals in receiving waters. ...
... 48 Instead, they are an in situ source of water-soluble contaminants, including those with toxic properties like 6PPD-quinone, for at least several years. 48 As such, there is a need to evaluate the relative contribution of vehicle tires on-road vs worn tire particles, particles embedded in the road vs free, and particles leaching in situ vs mobilized with runoff to the load of tire-derived chemicals in receiving waters. In concert, future research will invariably address the occurrence of 6PPD-quinone and other TWP-derived chemicals in aquatic environments and begin assessing additional species for adverse outcomes. ...
Tire tread wear particles (TWP) are increasingly recognized as a global pollutant of surface waters, but their impact on biota in receiving waters is rarely addressed. In the developed U.S. Pacific Northwest, acute mortality of adult coho salmon (Oncorhynchus kisutch) follows rain events and is correlated with roadway density. Roadway runoff experimentally triggers behavioral symptoms and associated changes in blood indicative of cardiorespiratory distress prior to death. Closely related chum salmon (O. keta) lack an equivalent response. Acute mortality of juvenile coho was recently experimentally linked to a transformation product of a tire-derived chemical. We evaluated whether TWP leachate is sufficient to trigger the acute mortality syndrome in adult coho salmon. We characterized the acute response of adult coho and chum salmon to TWP leachate (survival, behavior, blood physiology) and compared it with that caused by roadway runoff. TWP leachate was acutely lethal to coho at concentrations similar to roadway runoff, with the same behaviors and blood parameters impacted. As with runoff, chum salmon appeared insensitive to TWP leachate at concentrations lethal to coho. Our results confirm that environmentally relevant TWP exposures cause acute mortalities of a keystone aquatic species.
... Benzothiazoles and their derivates are heterocyclic compounds; together with dyphenylguanidine are used as accelerators in rubber production (Fishbein, 1991;De Wever and Verachtert, 1997). These compounds were detected in car tyre rubber leachates (Unice et al., 2015;Capolupo et al., 2020Capolupo et al., , 2021, inducing toxicity in fish and crustaceans (Sheftel, 2000;Chibwe et al., 2021;Halle et al., 2021;Bournaka et al., 2023). The 2,2,4-trimethyl-1H-quinoline is a common tyre antioxidant, responsible for a high toxicity in aquatic organisms . ...
... Leaching determines the bioavailability of chemicals. In general, only a small fraction of the chemicals in tyre rubber is available (Unice et al, 2015). Bioavailability depends on the particle size and the environmental conditions, such as the pH, as well as on the solubility of the substance. ...
The rubber tyre case study (RTC) is one of the case studies within the European NMBP13 projects, that are active in 2019-2023 with the development and establishment of a solid, well-balanced nano risk governance approach for Europe. The RTC investigates what can be learned from applying this nano risk governance approach to the problem of tyre wear generated by car driving activities. Within the frame of the NMBP13 project there is a special focus on the nanomaterials. As part of the RTC, this technical reference document collects available risk-related scientific information about environmental release of tyre wear particles (TWP) and its hazards. TWP generally associates with road wear to form TRWP (Tyre and Road Wear Particles). The particles’ size distribution concerns coarse, micro-sized and nano-sized particles and its associates.
From this literature research, the main obstacle to clearly understanding the contribution of nano-TWP to the health and environmental problem is the predominant use of the mass metric for measurements, rather than particle numbers. As a result, the 'nano contribution' is often ignored (van Broekhuizen 2022). Still, there are a few recent publications explicitly measuring real-life particle number-based concentrations of nano-TWP (Dahl et al 2006, Mathissen et al 2011, Beji et al 2021). Also, the relevance of a specific focus on nano, within the context of TWP release and the microplastics problem gains growing political attention (OECD 2014, 2020, 2020a), but suffers a huge shortage of relevant real-life measurements (Andersson-Sköld et al (2020), Mennekes et al 2022). TWP associates (agglomeration and/or aggregation) with road wear particles, which are collectively referred to as tyre and road wear particles (TRWP). TWP is estimated to contribute up to 30-50% to the TRWP mass (Simons et al 2016; Järlskog et al 2020).
... Several organic chemicals are added to the composition of tire rubber to facilitate polymerization during manufacturing or to increase performance and longevity. Among the numerous organic compounds added, 2-mercaptobenzothiazole (2-MBT) and 1,3-diphenylguanidine (DPG) are intensively used as vulcanization agents and can represent up to 0.5 % of the tire rubber (Masset et al., 2022;Unice et al., 2015). Phenylenediamine compounds, such as N-isopropyl-N′-phenyl-p-phenylenediamine (IPPD) and N-(1,3-dimethylbutyl)-N′-phenyl-1,4-phenylenediamine (6PPD), are additionally used as antioxidants and antiozonants (up to 4 % of the tire tread) in the final product to prevent cracking and degradation of the rubber during wear (Layer and Lattimer, 1990;Masset et al., 2022). ...
... TRWPs are anticipated to initially reside on the road or the roadside and primarily disperse through stormwater effluents, road runoff and wastewater treatment plant effluents, thereby reaching various environmental compartments, including aquatic and terrestrial ecosystem Xu et al., 2020). 1,3-Diphenylguanidine (DPG) has emerged as one of the highly leachable compounds in recent years (Jin et al., 2021;Müller et al., 2022;Seiwert et al., 2020;Unice et al., 2015;Wagner et al., 2018). As a secondary vulcanization accelerator and polymer additive commonly employed in the rubber industry, the presence of DPG has been widely observed in water samples worldwide, with concentrations ranging from ng/L to mg/L (Marques Dos Santos et al., 2022;Müller et al., 2022;Schulze et al., 2019;Zahn et al., 2019). ...
... human metabolism, especially with regard to applications in the food sector [9,11,12]. Furthermore, these structures were shown to leach from the polymer matrix and demonstrably contaminate the environment [13][14][15]. In view of the described issues and the sustainability aspect, bio-based antioxidants are of great academic and economic interest. ...
Antioxidants (AOs) from natural resources are an attractive research area, as petroleum-based products can be replaced in polymer stabilization. Therefore, novel esters based on the p-hydroxycinnamic acids p-coumaric acid, ferulic acid and sinapic acid were synthesized and their structure properties relationships were investigated. The structures of the novel bio-based antioxidants were verified using NMR and Fourier-transform infrared (FTIR) spectrometry. The high thermal stability above 280 °C and, therefore, their suitability as potential plastic stabilizers were shown using thermal gravimetric analysis (TGA). The radical scavenging activity of the synthesized esters was evaluated by using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Stabilization performance was evaluated in polypropylene (PP) using extended extrusion experiments, oxidation induction time (OIT) measurements and accelerated heat aging. In particular, the sinapic acid derivative provides a processing stability of PP being superior to the commercial state-of-the-art stabilizer octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.
... Thus, these compounds are not specific for tires and cannot be used as markers for tire wear quantification. However, there are several other organic compounds related to tires that have been suggested as markers for tire wear particles (Table 1).These include benzothiazoles which are impurities or decomposition products originated from sulphur cure accelerators of benzothiazole sulphonamides [34,61], diphenylguanidine (DPG) [62], oleamide [41], hydrogenated resin acids [32] and N-(1,3-dimethylbutyl)-N 0 -phenyl-pphenylenediamine-quinone (6-PPD-Q) [63]. The benzothiazole derivative 2-(4-morpholinyl) benzothiazole (24MoBT), a minor component in the vulcanization accelerator N-oxydiethylenebenzothiazolylsulfenamide (OBS), was one of the first organic markers applied for TRWP quantification (Appendix Table AP1) [33]. ...
As one of the largest sources of microplastic particle emissions, tire-road wear particle mixtures (TRWPs) pose a potentially high threat to various environmental compartments. Their heterogenous properties, from varying particle size, density, shape, texture, elemental and chemical composition, cause challenging analytical workflows. Current analytical methods for TRWP can be summarized in two main groups: single-particle-based and bulk-based methods. Both groups include a large variation of methods, with different demands for sampling and sample pre-treatment, and different possible outputs. This review provides an overview of the current analytical methods used for TRWP studies and in particularly quantifications, with focus on methods that have been peer-reviewed and tested for environmental samples. The review presents current possibilities and limitations with the different analytical approaches, as well as highlighting gaps in the current TRWP knowledge and information needed to move this research field forward.
... It has been shown that tire wear is a major source of PPDs in the environment (Huang et al., 2021). In addition to the abovementioned additives, the conversion products of 6PPD have been identified in TRWMPs, including 4-aminodiphenylamine (4-ADPA), 4-nitrodiphenylamine (4-NDPA), 4-hydroxydiphenylamine (4-HDPA), and diphenylamine (DPA) (Klöckner et al., 2021;Unice et al., 2015). ...
Tire and road wear microplastics (TRWMPs) are one of the main non-exhaust pollutants of motor vehicles, which cause serious environmental and health issues. Here, TRWMPs in PM2.5 samples were collected in a tunnel in urban Xi'an, northwest China, during four periods [I: 7:30-10:30, II: 11:00-14:00, III: 16:30-19:30, IV: 20:00-23:00 local standard time (LST)] in summer of 2019. The chemical components of rubbers, benzothiazoles, phthalates, and amines in TRWMPs were quantified, with a total concentration of 6522 ± 1455 ng m-3 (mean ± standard deviation). Phthalates were predominant in TRWMPs, accounting for 64.8% on average, followed by rubbers (33.2%) and benzothiazoles (1.19%). The diurnal variations of TRWMPs showed the highest concentration in Period III (evening rush hour) and the lowest concentration in Period I (morning rush hour), which were not exactly consistent with the variation of the number of light-duty vehicles passed through the tunnel. The result implied that the number of vehicles might not be the most important contributor to TRWMPs concentration, whereas meteorological variables (i.e., precipitation, and relative humidity), vehicle speed, vehicle class, and road cleaning also affected their abundances. The non-carcinogenic risk of TRWMPs in this study was within the international safety threshold, but their carcinogenic risk exceeded the threshold by 2.7-4.6 times, mostly dominated by bis(2-ethylhexyl)phthalate (DEHP). This study provides a new basis for the source apportionment of urban PM2.5 in China. The high concentrations and high potential cancer risks of TRWMPs represent the requirement for more efficient measures to control light-duty vehicle emissions.
... 1,3-diphenylguanidine (1,3-DPG)] are freely leached from TWPs in the environment and are frequently associated with urban stormwater mortality signatures for several sensitive organisms (Peter et al. 2018, Wiener andLefevre 2022). Up to 14% of the initial tire mass is attributable to these compounds, accounting for 1.3 kg released over the lifetime of a tire (Unice et al. 2015). ...
Aim:
Stormwater is a major source of many contaminants of emerging concern, which can be toxic to both aquatic and terrestrial organisms. This project aimed to identify novel biodegraders of toxic tire wear particle contaminants associated with coho salmon mortality.
Methods and results:
This study has: i) characterized the prokaryotic communities of stormwater in both urban and rural settings; ii) evaluated the ability of stormwater isolates to degrade two model tire wear particle contaminants, hexa(methoxymethyl)melamine and 1,3-diphenylguanidine; and iii) evaluated the toxicological impact of these model contaminants on the growth of six model bacteria. Rural stormwater possessed a diverse microbiome dominated by Oxalobacteraceae, Microbacteriaceae, Cellulomonadaceae, and Pseudomonadaceae taxa, while urban stormwater showed much less microbial diversity overall. Additionally, multiple stormwater isolates appeared capable of using model tire wear particle contaminants as their sole carbon source. Each model contaminant was also found to alter growth patterns of model environmental bacteria including, with 1,3-DPG appearing more acutely toxic at high concentrations.
Conclusion:
This study identified several stormwater isolates that have the potential to be used as a sustainable solution to stormwater quality management.
... 1,3-Diphenylguanidine (DPG) is a PMOC that is used as a vulcanization accelerator in rubber products such as tires [8,9]. It was detected as one of the main leachables in lab-scale tire wear extraction experiments [10] and was classified as a tire-related chemical in source-related smart suspect screening in water [11]. ...
Persistent and mobile organic compounds (PMOCs) are highly soluble in water, thereby posing a threat to water resource quality. Currently, there are no methods that can accurately quantify guanidine derivative PMOCs, other than 1,3-diphenylguanidine (DPG) and cyanoguanidine (CG), in aqueous media. In this study, we developed a quantitation method that combines solid-phase extraction and liquid chromatography (LC)-tandem mass spectrometry to detect seven guanidine derivatives in aquatic environments and applied it to environmental water samples. Five LC columns were examined, and among them, a hydrophilic interaction liquid chromatography column was chosen owing to its suitable instrument detection limit and retention factor. Method precision was assessed using seven replicate analyses of river water. The corresponding analyte recoveries ranged from 73 to 137% (coefficient of variation = 2.1–5.8%). DPG and CG were detected in ultrapure water samples at levels up to 0.69 and 150 ng L ⁻¹ , respectively; DPG and CG levels up to 44 and 2600 ng L ⁻¹ , respectively, were detected in lake water, river water, sewage effluent, and tap water sampled in Western Japan. This is the first reported detection of DPG in the surface water of Japan, revealing that DPG and CG are ubiquitous compounds in aquatic environments. Moreover, this is the first study to detect 1-( o -tolyl)biguanide and N , N′′′ -1,6-hexanediylbis( N′ -cyanoguanidine) in water. This study provides a foundation for further research on the distribution, fate, and emission source of these pollutants, which is critical to maintain high water quality and to determine regulatory limits for these pollutants.
Graphical Abstract
... N-O stretching of nitro compounds are represented by the peaks between 1560 cm − 1 and 1506 cm − 1 (Varrica et al., 2019;. Certain nitrogenous compounds have also been reported by Unice et al. (2015), suggesting release of chemicals used in tires: N-cyclohexylbenzothiazole-2-sulfenamide, N-(1,3-dimethylbutyl)-N ′ -phenyl-1, 4-phenylenediamine and 1,3-diphenylguanidine. There were certain events of burning of tires near sampling site. ...
The development-oriented anthropogenic activities have led to intensive increase in emission of various organic pollutants, which contribute considerably to human health risk. In the present study, chemical, physical and spectral characterisation of fine particulate matter (PM2.5), collected at Faridabad city, in northern India, were examined. Seasonal variation of organic compounds [n-alkanes, polyaromatic hydrocarbons (PAHs) and phthalic acid esters (PAEs)], and potential health risk of Polyaromatic hydrocarbons (PAHs) exposure using toxic equivalency potential (TEQ) approach had been assessed. These showed seasonal average values ranging from 156.4 ± 57.0 ng/m³ to 217.6 ± 72.9 ng/m³, 98.0 ± 21.4 ng/m³ to 177.8 ± 72.8 ng/m³, and 30.9 ± 11.9 ng/m³ to 82.5 ± 29.2 ng/m³, respectively, with the highest value for winter. It is noteworthy that unlike, n-alkanes and PAEs, PAHs were least during spring. The high molecular weight PAHs (BaP, BkF, DahA and IcdP) were found to exhibit higher TEQ values (ranging from 0.7 to 9.7) despite of their lower concentrations. The PAH diagnostic ratio, carbon preference index and total index revealed the enhanced impact of biogenic sources of emissions in comparison to diesel emission sources during winter.
... Leaching determines the bioavailability of chemicals. In general, only a small fraction of the chemicals in tyre rubber is available (Unice et al, 2015). Bioavailability depends on the particle size and the environmental conditions, such as the pH, as well as on the solubility of the substance. ...
The rubber tyre case study (RTC) is one of the case studies within the European NMBP13 projects, that are active in 2019-2023 with the development and establishment of a solid, well-balanced nano risk governance approach for Europe. The RTC investigates what can be learned from applying this nano risk governance approach to the problem of tyre wear generated by car driving activities. Within the frame of the NMBP13 project there is a special focus on the nanomaterials.
As part of the RTC, this paper collects available risk-related scientific information about environmental release of tyre wear particles (TWP), which generally associates with road wear to form TRWP (Tyre and Road Wear Particles). The particles’ size distribution concerns coarse, micro-sized and nano-sized particles and its associates.
Key questions concerned in this study are: ‘What are the risks of nanoparticles released during the use of rubber tyres?’ And if there are risks, how could these be controlled?
... More recent estimates put the yearly usage of DPG up to 10,000 metric tons in Europe alone (ECHA, 2018). DPG has been identified as one of the main components leached from tire particles (Seiwert et al., 2020;Unice et al., 2015;Wik and Dave, 2009;Zahn et al., 2019) and being ubiquitously found in water sample across the globe from low ng/L to mg/L concentrations. Previous studies have also reported the migration of DPG from HDPE pipes resulting in water sample with concentrations ranging from 0.12 to 0.74 mg/L . ...
1,3-diphenylguanidine (DPG) is a commonly used rubber and polymer additive, that has been found to be one of the main leachate products of tire wear particles and from HDPE pipes. Its introduction to aquatic environments and potentially water supplies lead to further questions regarding the effects of disinfection by-products potentially formed. Using different bioassay approaches and NGS RNA-sequencing, we show that some of the chlorinated by-products of DPG exert significant toxicity. DPG and its chlorinated by-products also can alter cell bioenergetic processes, affecting cellular basal respiration rates and ATP production, moreover, DPG and its two chlorination products, 1,3-bis-(4-chlorophenyl)guanidine (CC04) and 1-(4-chlorophenyl)-3-(2,4-dichlorophenyl)guanidine (CC11), have an impact on mitochondrial proton leak, which is an indicator of mitochondria damage. Evidence of genotoxic effects in the form of DNA double strand breaks (DSBs) was suggested by RNA-sequencing results and further validated by an increased expression of genes associated with DNA damage response (DDR), specifically the canonical non-homologous end joining (c-NHEJ) pathway, as determined by qPCR analysis of different pathway specific genes (XRCC6, PRKDC, LIG4 and XRCC4). Immunofluorescence analysis of phosphorylated histone H2AX, another DSB biomarker, also confirmed the potential genotoxic effects observed for the chlorinated products. In addition, chlorination of DPG leads to the formation of different chlorinated products (CC04, CC05 and CC15), with analysed compounds representing up to 42% of formed products, monochloramine is not able to effectively react with DPG. These findings indicate that DPG reaction with free chlorine doses commonly applied during drinking water treatment or in water distribution networks (0.2-0.5 mg/L) can lead to the formation of toxic and genotoxic chlorinated products.
... As an antioxidant, 6PPD is designed to react readily and produce transformation products including 6PPD-Q. It is known that chemicals other than 6PPD-Q are newly formed in road, atmospheric, and aquatic environments (Klöckner et al., 2021a;Unice et al., 2015). These transformation products may possess physicochemical properties and exert biological effects that are different from those of the parent chemical, 6PPD, as demonstrated by the example of 6PPD-Q (Tian et al., 2021); therefore, further research is needed to investigate not only the environmental occurrence and fate, but also the ecotoxicological impacts, of these transformation products. ...
A recently identified chemical, 2-((4-Methylpentan-2-yl)amino)-5-(phenylamino)cyclohexa-2,5-diene-1,4-dione (6PPD-quinone; 6PPD-Q), is a transformation product of an additive used in the manufacture of tire rubber and causes acute lethality in coho salmon (Oncorhynchus kisutch) in urban watersheds. Despite its potential presence and ecotoxicity in receiving waters worldwide, information on the occurrence and fate of 6PPD-Q is limited. Here, we investigated the concentrations of 6PPD-Q and its parent chemical, 6PPD, in road dust collected from arterial and residential roads in Tokyo, Japan from May to October 2021. 6PPD-Q concentrations were highest from May to June, when atmospheric ozone concentrations are the highest in Japan; a correlation between 6PPD-Q and photochemical oxidants, as an alternative to ozone, corroborated this finding. We also found that 6PPD-Q concentrations at photochemical oxidant concentrations ranging from 35 to 47 ppbv were higher in dust collected from roads with high traffic volumes (i.e., arterial roads; median: 8.6 μg/g-OC) than in dust collect from roads with lower traffic volumes (i.e., residential roads; median: 6.3 μg/g-OC), indicating that 6PPD-Q is generated from traffic-related sources. We also found that 6PPD-Q was leached from dust particles within a few hours, with a log partitioning coefficient between organic carbon and water (KOC) of about 3.0. The present results will help to understand the environmental occurrence, fate, and behavior of 6PPD-Q.
... About 60% of the leachables were classified as mobile compounds, indicating a large potential for transport in the environment (Müller et al., 2022)). Examples of tire-derived chemicals that have been found to be harmful to organisms are benzothiazoles, N-1,3dimethylbutyl-N 0-phenyl-p-phenylenediamine (6-PPD), 1,3-diphenylguanidine (DPG) and different polycyclic aromatic hydrocarbons (PAHs) (Halsband et al., 2020;Seiwert et al., 2020;Tian et al., 2021;Unice et al., 2015). ...
According to estimates put forward in multiple studies, tire and road wear particles are one of the largest sources to microplastic contamination in the environment. There are large uncertainties associated with local emissions and transport of tire and road wear particles into environmental compartments, highlighting an urgent need to provide more data on inventories and fluxes of these particles. To our knowledge, the present paper is the first published data on mass concentrations and snow mass load of tire and polymer-modified road wear particles in snow. Roadside snow and meltwater from three different types of roads (peri-urban, urban highway and urban) were analysed by Pyrolysis Gas Chromatography Mass Spectrometry. Tire particle mass concentrations in snow (76.0-14,500 mg/L meltwater), and snow mass loads (222-109,000 mg/m2) varied widely. The concentration ranges of polymer-modified particles were 14.8-9550 mg/L and 50.0-28,800 mg/m2 in snow and meltwater, respectively. Comparing the levels of tire and PMB particles to the total mass of particles, showed that tire and PMB-particles combined only contribute to 5.7% (meltwater) and 5.2% (mass load) of the total mass concentration of particles. The large variation between sites in the study was investigated using redundancy analysis of the possible explanatory variables. Contradictory to previous road studies, speed limit was found to be one of the most important variables explaining the variation in mass concentrations, and not Annual Average Daily Traffic. All identified variables explained 69% and 66%, for meltwater and mass load concentrations, respectively. The results show that roadside snow contain total suspended solids in concentrations far exceeding release limits of tunnel and road runoff, as well as tire particles in concentrations comparable to levels previously reported to cause toxicity effects in organisms. These findings strongly indicate that roadside snow should be treated before release into the environment.
... About 60% of the leachables were classified as mobile compounds, indicating a large potential for transport in the environment (Müller et al., 2022). Examples of tirederived chemicals that have been found to be harmful to organisms are benzothiazoles, N-1,3-dimethylbutyl-N 0-phenyl-p-phenylenediamine (6-PPD), 1,3-diphenylguanidine (DPG) and different polycyclic aromatic hydrocarbons (PAHs) (Halsband et al., 2020;Seiwert et al., 2020;Tian et al., 2021;Unice et al., 2015). ...
... The suspect screening analyses tentatively identified N,N′-diphenylguanidine (DPG), N,N-dicyclohexylmethylamine (DCA), N,N′dicyclohexylurea (DCU), and 1-cyclohexyl-3-phenylurea (CPU) in the storm runoff and snowmelt samples. These four bicyclic amines are associated with tire rubber manufacturing and have been detected in tire rubber leachate, 28 and road runoff. 7,13 These four compounds also had readily available authentic standards. ...
Recent findings that 2-anilo-5-[(4-methylpentan-2-yl)amino]cyclohexa-2,5-diene-1,4-dione (6PPD-quinone), the transformation product of a common tire rubber antioxidant, is acutely toxic in stormwater-impacted streams has highlighted the need for a better understanding of contaminants in urban runoff. This study represents one of the first reports of 6PPD-quinone and other tire rubber-derived compounds in stormwater and snowmelt of a cold-climate Canadian city (Saskatoon, 2019–2020). Semiquantification of the five target compounds, N,N′-diphenylguanidine (DPG), N,N-dicyclohexylmethylamine (DCA), N,N′-dicyclohexylurea (DCU), 1-cyclohexyl-3-phenylurea (CPU), and 6PPD-quinone, revealed DPG was most abundant, with average concentrations of 60 μg L–1 in stormwater and 1 μg L–1 in snowmelt. Maximum observed concentrations of DPG were greater than 300 μg L–1, equivalent to loadings of 15 kg from a single rain event. These concentrations of DPG represent some of the highest reported in urban runoff globally. 6PPD-Quinone was detected in 57% (12/21) of stormwater samples with a mean concentration of approximately 600 ng L–1 (2019) and greater than 80% (28/31) of snowmelt samples with mean concentrations of 80–370 ng L–1 (2019 and 2020). Concentrations of 6PPD-quinone exceeded the acute LC50 for coho salmon (0.8–1.2 μg L–1) in greater than 20% of stormwater samples. Mass loadings of all target chemicals correlated well with roads and residential land-use area.
Fluridone is an aquatic herbicide commonly used to treat invasive freshwater plant species such as Eurasian watermilfoil, hydrilla, and curly-leaf pondweed. However, required exposures times are very long and often...
Numerous toxic substances are directly and indirectly discharged by humans into water bodies, causing distress to the organisms living on it. 6PPD, an amino antioxidant from tires reacts with ozone to form 6PPD-Q, which has garnered global attention due to its lethal nature to various organisms. This review aims to provide an understanding of the sources, transformation, and fate of 6PPD-Q in water and the current knowledge on its effects on aquatic organisms. Furthermore, we discuss research gaps pertaining to the mechanisms by which 6PPD-Q acts within fish bodies. Previous studies have demonstrated the ubiquitous presence of 6PPD-Q in the environment, including air, water, and soil. Moreover, this compound has shown high lethality to certain fish species while not affecting others. Toxicological studies have revealed its impact on the nervous system, intestinal barrier function, cardiac function, equilibrium loss, and oxidative stress in various fish species. Additionally, exposure to 6PPD-Q has led to organ injury, lipid accumulation, and cytokine production in C. elegans and mice. Despite studies elucidating the lethal dose and effects of 6PPD-Q in fish species, the underlying mechanisms behind these symptoms remain unclear. Future studies should prioritize investigating the mechanisms underlying the lethality of 6PPD-Q in fish species to gain a better understanding of its potential effects on different organisms.
Tire wear particles (TWPs) are increasingly being found in the aquatic environment. However, there is limited information available on the environmental consequences of TWP constituents that may be release into water. In this study, TWP leachate samples were obtained by immersing TWPs in ultrapure water. Using high-resolution mass spectrometry and toxicity identification, we identified potentially toxic organic substances in the TWP leachates. Additionally, we investigated their toxicity and underlying mechanisms. Through our established workflow, we structurally identified 13 substances using reference standards. The median effective concentration (EC50) of TWP leachates on Scenedesmus obliquus growth was comparable to that of simulated TWP leachates prepared with consistent concentrations of the 13 identified substances, indicating their dominance in the toxicity of TWP leachates. Among these substances, cyclic amines (EC50: 1.04-3.65 mg/L) were found to be toxic to S. obliquus. We observed significant differential metabolites in TWP leachate-exposed S. obliquus, primarily associated with linoleic acid metabolism and purine metabolism. Oxidative stress was identified as a crucial factor in algal growth inhibition. Our findings shed light on the risk posed by TWP leachable substances to aquatic organisms.
Stormwater runoff from roadways is a global threat to water quality, aquatic organisms, and ecosystems. Tire tread wear particles (TWP) from roadway runoff may lead to urban runoff mortality syndrome (URMS) in some aquatic organisms. We tested the hypothesis that urban runoff from roadways can kill zooplankton. Both roadway runoff and TWP leachate were acutely lethal to a model species, the water flea Daphnia pulex. Life table experiments further revealed the lowered survival rates, intrinsic rate of increase, average life span, and net productive rate of D. pulex when exposed to roadway runoff and TWP leachate. The tire rubber antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) mainly contributed to the TWP toxicity. The toxicity of TWP and 6PPD extracted varied with time in nature. Cladocerans and rotifers were more sensitive to TWP and 6PPD than copepods. These results demonstrate the presence of URMS in zooplankton, which may cascade through food webs and affect aquatic ecosystems.
Recently, roadway releases of N,N'-substituted p-phenylenediamine (PPD) antioxidants and their transformation products (TPs) received significant attention due to the highly toxic 6PPD-quinone. However, the occurrence of PPDs and TPs in recycled tire rubber products remains uncharacterized. Here, we analyzed tire wear particles (TWPs), recycled rubber doormats, and turf-field crumb rubbers for seven PPD antioxidants, five PPD-quinones (PPDQs), and five other 6PPD TPs using liquid chromatography-tandem mass spectrometry. PPD antioxidants, PPDQs, and other TPs were present in all samples with chemical profiles dominated by 6PPD, DTPD, DPPD, and their corresponding PPDQs. Interestingly, the individual [PPDQ]/[PPD] and [TP]/[PPD] ratios significantly increased as total concentrations of the PPD-derived chemical decreased, indicating that TPs (including PPDQs) dominated the PPD-derived compounds with increased environmental weathering. Furthermore, we quantified 15 other industrial rubber additives (including bonding agents, vulcanization accelerators, benzotriazole and benzothiazole derivatives, and diphenylamine antioxidants), observing that PPD-derived chemical concentrations were 0.5-6 times higher than these often-studied additives. We also screened various other elastomeric consumer products, consistently detecting PPD-derived compounds in lab stoppers, sneaker soles, and rubber garden hose samples. These data emphasize that PPD antioxidants, PPDQs, and related TPs are important, previously overlooked contaminant classes in tire rubbers and elastomeric consumer products.
N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) is a globally ubiquitous tire rubber antioxidant. Its transformation product, 6PPD-quinone, has been identified as a potent toxicant responsible for the acute mortality of coho salmon in Pacific Northwest during storm events, a phenomenon called “urban runoff mortality syndrome” that persists for decades. As a consequence, there has been mounting interest in understanding the occurrence, environmental fate and biotoxicity of this emerging contaminant. In this article, we review the current status of mass spectrometry (MS) as a preeminent analytical tool for analysis of 6PPD-quinone across multiple environmental compartments, including urban road runoff and watersheds, dust, and fine particulate matters. Novel strategies and refinements for MS data acquisition and the synergistic use of chromatographic techniques for enhanced identification and quantification are introduced. Concurrently, we summary the technical dissimilarities between currently available methods regarding their instrumental settings, data acquisition modes, and analytical performance. In addition, we highlight the utility of MS-based methodologies for interrogation of toxicological effects of 6PPD-quinone in living organisms, especially aquatic species. Finally, we comment on the foreseen applications of MS-based techniques for better understanding environmental relevance, ecological toxicity, and human exposure risks of this emerging contaminant.
Laboratory studies used to assess the environmental
fate of organic chemicals such as pesticides fail to replicate
environmental conditions, resulting in large errors in predicted
transformation rates. We combine laboratory and field data to
identify the dominant loss processes of the herbicide 2,4-
dichlorophenoxyacetic acid (2,4-D) in lakes for the first time.
Microbial and photochemical degradation are individually assessed
using laboratory-based microcosms and irradiation studies,
respectively. Field campaigns are conducted in six lakes to quantify
2,4-D loss following large-scale herbicide treatments. Irradiation
studies show that 2,4-D undergoes direct photodegradation, but
modeling efforts demonstrated that this process is negligible under
environmental conditions. Microcosms constructed using field inocula show that sediment microbial communities are responsible
for degradation of 2,4-D in lakes. Attempts to quantify transformation products are unsuccessful in both laboratory and field studies,
suggesting that their persistence is not a major concern. The synthesis of laboratory and field experiments is used to demonstrate
best practices in designing laboratory persistence studies and in using those results to mechanistically predict contaminant fate in
complex aquatic environments.
The environmental threat represented by tire and road wear particles (TRWPs) has highlighted the need for effective analytical strategies for their detection and quantitation in different matrices. To date, however, there is little consensus in the literature on how to obtain reliable data on TRWPs in environmental samples, which chemical marker should be used, and how analytical results can be correlated with the amount of particulate. This review compares the analytical strategies described in the literature from a critical point of view and outlines the most crucial aspects, giving an overview of the current knowledge and discussing the analytical challenges that need to be addressed. The literature highlights the critical role played by the selection of detection and quantitation markers, the variations in the formulation of the tires, the environmental degradation pathways of TRWPs components, and the effects of the sample matrix and composition on the analytical response.
The antiozonant N-phenyl-N’-(1,3-dimethylbutyl)-p-phenylenediamine (6-PPD) is added to tires to increase their lifetime and is emitted with tire and road wear particles into the environment. Recently, one of its transformation products (TPs), 6-PPD quinone (6-PPDQ), has gained attention due to its toxicity towards coho salmon. In this study, the abiotic oxidative transformation of 6-PPD is investigated by a series of ozonation experiments in the lab followed by analysis of TPs using liquid chromatography-high resolution-mass spectrometry (LC-HRMS). A total of 38 TPs were detected and tentatively identified, which were formed either directly from 6-PPD or via 6-PPDQ as intermediate. A suspect screening by LC-HRMS showed 32 of these TPs to occur in snow collected from urban roads as surrogate of road-runoff, where 6-PPDQ, 4-aminodiphenylamine (4-ADPA), TP 213, and TP 249 were the most prominent besides 6-PPD. More than 90% of the total load of 6-PPD and its TPs was found in the particulate fraction of snow. Thus, retaining the particulate fraction of road runoff before its discharge into surface water would substantially reduce the emission of 6-PPD and many of its TPs. Some TPs prevailed in the water phase of the snow due to their higher polarity. A total of 13 TPs were detected by suspect screening in the dissolved phase of a wastewater treatment plant (WWTP) influent. Their total load was markedly enhanced during a day of snowmelt (approx. 1100 g/d) and rainfall (approx. 2000 g/d) compared to dry weather (approx. 190 g/d). 6-PPD and 6-PPDQ contributed to less than 1% to this total load in the water phase (estimated concentrations of max 0.1 µg/L). The elimination of the estimated total loads of 6-PPD related TPs from the water phase in WWTP ranged from 22 to 67% depending on weather conditions. Eventually TP 249, 4-ADPA and TP 259_2 dominated in WWTP effluent (estimated concentration from 0.5 up to 2 µg/L). Thus TP 249 and TP 259_2 are, likely, the most specific and stable TPs of 6-PPD to be determined in the environment.
Tire-derived particles and polyethylene (PE) debris co-exist in estuaries and potentially deteriorate water quality. Chemicals can be emitted from tire-derived particles and resorb to PE debris. However, there was lack of information about the interaction (e.g., sorption and desorption) between tire-derived chemicals and PE debris. By combining batch sorption and desorption experiments along with in situ field deployment of PE sheets, we examined the utility of benzothiazoles (BTZs) sorbed in PE as suitable markers of tire-derived inputs. The sorptive characteristics and PE-water partition coefficients (often designated as Kpew) of selected tire-derived marker candidates, i.e., polycyclic aromatic hydrocarbons (PAHs), benzothiophenes (BTPs) and BTZs, were measured. Moderately polar BTPs and BTZs (except for 2-(4-morpholinyl) benzothiazole) reached equilibrium within 2–8 days, compared to 20 days for nonpolar PAHs. The measure Kpew values and octanol-water partition coefficients of PAHs, BTPs and BTZs were linearly correlated with each other (r² > 0.80; p < 0.05). The desorption potentiality of PAHs and BTZs from tire particles is consistent with the hydrophilic properties of the target chemicals, while desorption ratios of BTZs and PAHs are 25–87% and <20%, respectively. Samplers with PE sheets as the sorbent phase were deployed in Hailing Bay, an urbanized estuary in South China, to measure concentrations of PAHs, BTPs and BTZs. Benzothiazoles sorbed in PE samples were associated with the massive utilization of automobile tires, while PAHs were linked to the boat maintenance facilities and BTPs were not detected in any tire particle and field PE samples. Therefore sorbed BTZs in PE can potentially serve as chemical markers of tire-derived inputs to estuaries.
The environmental fate of tire and road wear particles (TRWPs) receives increasing attention due to the per capita emission volumes of 0.2–5.5 kg/(cap year) and recent reports on the environmental hazard of TRWP constituents. It is expected that aging impacts TRWPs fate in the environment but detailed knowledge is quite limited, yet. Making use of information on tire aging, the available knowledge on environmental aging processes such as thermooxidation, photooxidation, ozonolysis, shear stress, biodegradation and leaching is reviewed here. Experimental techniques to simulate aging are addressed as are analytical techniques to determine aging induced changes of TRWPs, covering physical and chemical properties. The suitability of various tire wear test materials is discussed. Findings and methods from tire aging can be partially applied to study aging of TRWPs in the environment. There is a complex interplay between aging processes in the environment that needs to be considered in future aging studies. In addition to existing basic qualitative understanding of the aging processes, quantitative understanding of TRWP aging is largely lacking. Aging in the environment needs to consider the TRWPs as well as chemicals released. Next steps for filling the gaps in knowledge on aging of TRWPs in the environment are elaborated.
Tire and road wear particles (TRWP) consist of a complex mixture of rubber, and pavement released from tires during use on road surfaces. Subsequent transport of the TRWP into freshwater sediments has raised some concern about the potential adverse effects on aquatic organisms. Previous studies have shown some potential for toxicity for tread particles, however, toxicity studies of TRWP collected from a road simulator system revealed no acute toxicity to green algae, daphnids, or fathead minnows at concentrations up to 10,000 mg/kg under conditions representative of receiving water bodies. In this study, the chronic toxicity of TRWP was evaluated in four aquatic species. Test animals were exposed to whole sediment spiked with TRWP at concentrations up to 10,000 mg/kg sediment or elutriates from spiked sediment. Exposure to TRWP spiked sediment caused mild growth inhibition in Chironomus dilutus but had no adverse effect on growth or reproduction in Hyalella azteca. Exposure to TRWP elutriates resulted in slightly diminished survival in larval Pimephales promelas but had no adverse effect on growth or reproduction in Ceriodaphnia dubia. No other endpoints in these species were affected. These results, together with previous studies demonstrating no acute toxicity of TRWP, indicate that under typical exposure conditions TRWP in sediments pose a low risk of toxicity to aquatic organisms.
Human pharmaceutical active ingredients that are orally or parenterally administered may be metabolised in the body and after excretion may be further transformed in the receiving environmental compartments. The optimal outcome from an environmental point of view-complete mineralisation-is rarely observed. Small molecule pharmaceuticals are commonly not readily biodegradable according to Organisation for Economic Cooperation and Development (OECD) 301 tests. However, primary transformation is often observed. To gain information on the transformation of active ingredients in the environment, long-term studies like transformation in aquatic water/sediment systems according to OECD guideline 308 are required for the environmental risk assessment for human active pharmaceutical ingredients. Studies received until mid 2010 as part of the dossiers for marketing authorisation applications were evaluated concerning transformation products. The evaluation revealed that in 70 % of the studies, at least one transformation product (TP) is formed above 10 % of the originally applied dose, but in only 26 % of the studies are all TP identified. The evaluation also revealed that some TP of pharmaceutical active ingredients show a considerably longer DT50 compared to the parent compound. An example is the TP (val)sartan acid that is formed from an antihypertensive compound.
Pyrolysis(pyr)-GC/MS analysis of characteristic thermal decomposition fragments has been previously used for qualitative fingerprinting of organic sources in environmental samples. A quantitative pyr-GC/MS method based on characteristic tire polymer pyrolysis products was developed for tread particle quantification in environmental matrices including soil, sediment, and air. The feasibility of quantitative pyr-GC/MS analysis of tread was confirmed in a method evaluation study using artificial soil spiked with known amounts of cryogenically generated tread. Tread concentration determined by blinded analyses was highly correlated (r2 ³ 0.88) with the known tread spike concentration. Two critical refinements to the initial pyrolysis protocol were identified including use of an internal standard and quantification by the dimeric markers vinylcyclohexene and dipentene, which have good specificity for rubber polymer with no other appreciable environmental sources. A novel use of deuterated internal standards of similar polymeric structure was developed to correct the variable analyte recovery caused by sample size, matrix effects, and ion source variability. The resultant quantitative pyr-GC/MS protocol is reliable and transferable between laboratories.
Background, aim and scope
Over 50% of the global population live in urban centres and, therefore, an understanding of the processes acting upon urban systems is a global issue. The nature of human-made, often impervious, land surfaces and heavily engineered waterways results in hydrological and sedimentological systems in urbanised basins which contrast significantly to those within more natural (i.e. pristine, forested, agricultural) aquatic systems. In addition, the abundance of contamination sources in urban systems results in chemical pressures often manifested as high pollution concentrations or loadings, which in turn have detrimental impacts on human and ecosystem health. These lead to management and sustainability issues not generally encountered in more natural environments. The purpose of this review is to provide a state-of-the-art assessment of sediment sources, pathways and storage within urban river systems, to consider sediment management within urban systems and river basins, and examine the role of local and global environmental changes on sediment processes and management. Inevitably, much of the sediment that is transported within urbanised basins is contaminated, so this review also considers sediment–contaminant sources and interactions.
Conclusions and recommendations
We reach a number of conclusions and recommendations for future research. There is a need for better sampling and monitoring of sediment and sediment-associated contaminant fluxes and cycling in urban river channels and basins. This should include better techniques and studies to identify sources and transfers of road-deposited sediment (RDS), airborne particulate matter and sediments in the river system. Greater interdisciplinary research, combining sedimentologists, hydrologists, urban planners, urban archaeologists, chemists and biologists, is needed. More attention needs to focus on upscaling and connecting urban areas to the rest of the river basin, both upstream and downstream. Finally, there is a need to balance multiple needs (urban population, water resources) with likely trends in both urban development and global environmental change.
Previous studies have indicated that tire tread particles are toxic to aquatic species, but few studies have evaluated the toxicity of such particles using sediment, the likely reservoir of tire wear particles in the environment. In this study, the acute toxicity of tire and road wear particles (TRWP) was assessed in Pseudokirchneriella subcapita, Daphnia magna, and Pimephales promelas using a sediment elutriate (100, 500, 1000 or 10000 mg/l TRWP). Under standard test temperature conditions, no concentration response was observed and EC/LC(50) values were greater than 10,000 mg/l. Additional tests using D. magna were performed both with and without sediment in elutriates collected under heated conditions designed to promote the release of chemicals from the rubber matrix to understand what environmental factors may influence the toxicity of TRWP. Toxicity was only observed for elutriates generated from TRWP leached under high-temperature conditions and the lowest EC/LC(50) value was 5,000 mg/l. In an effort to identify potential toxic chemical constituent(s) in the heated leachates, toxicity identification evaluation (TIE) studies and chemical analysis of the leachate were conducted. The TIE coupled with chemical analysis (liquid chromatography/mass spectrometry/mass spectrometry [LC/MS/MS] and inductively coupled plasma/mass spectrometry [ICP/MS]) of the leachate identified zinc and aniline as candidate toxicants. However, based on the high EC/LC(50) values and the limited conditions under which toxicity was observed, TRWP should be considered a low risk to aquatic ecosystems under acute exposure scenarios.
Organic chemicals have been detected at trace concentrations in the freshwater environment for decades. Though the term trace pollutant indicates low concentrations normally in the nanogram or microgram per liter range, many of these pollutants can exceed an acceptable daily intake (ADI) for humans. Trace pollutants referred to as emerging contaminants (ECs) have recently been detected in the freshwater environment and may have adverse human health effects. Analytical techniques continue to improve; therefore, the number and frequency of detections of ECs are increasing. It is difficult for regulators to restrict use of pollutants that are a human health hazard; scientists to improve treatment techniques for higher priority pollutants; and the public to modify consumption patterns due to the vast number of ECs and the breadth of literature on the occurrence, use, and toxicity. Hence, this paper examines literature containing occurrence and toxicity data for three broad classes of trace pollutants and ECs (industrials, pesticides, and pharmaceuticals and personal care products (PPCPs)), and assesses the relevance of 71 individual compounds. The evaluation indicates that widely used industrials (BPF) and PPCPs (AHTN, HHCB, ibuprofen, and estriol) occur frequently in samples from the freshwater environment but toxicity data were not available; thus, it is important to establish their ADI. Other widely used industrials (BDE-47, BDE-99) and pesticides (benomyl, carbendazim, aldrin, endrin, ethion, malathion, biphenthrin, and cypermethrin) have established ADI values but occurrence in the freshwater environment was not well documented. The highest priority pollutants for regulation and treatment should include industrials (PFOA, PFOS and DEHP), pesticides (diazinon, methoxychlor, and dieldrin), and PPCPs (EE2, carbamazepine, βE2, DEET, triclosan, acetaminophen, and E1) because they occur frequently in the freshwater environment and pose a human health hazard at environmental concentrations.
Water solubility enhancements by dissolved humic and fulvic acids from soil and aquatic origins and by synthetic organic polymers have been determined for selected organic pollutants and pesticides (p,p'-DDT,2,4,5,2',5'-PCB, 2,4,4'-PCB, 1,2,3,-trichlorobenzene, and lindane). Significant solubility enhancements of relatively water-insoluble solutes by dissolved organic matter (DOM) of soil and aquatic origins may be described in terms of a partition-like interaction of the solutes with the microscopic organic environment of the high-molecular-weight DOM species; the apparent solute solubilities increase linearly with DOM concentration and show no competitive effect between solutes. The K/sub dom/ values of solutes with soil-derived humic acid are approximately 4 times greater than with soil fulvic acid and 5-7 times greater than with aquatic humic and fulvic acids. The effectiveness of DOM in enhancing solute solubility appears to be largely controlled by the DOM molecular size and polarity. The relative inability of high-molecular-weight poly(acrylic acids) to enhance solute solubility is attributed to their high polarities and extended chain structures that do not permit the formation of a sizable intramolecular nonpolar environment. 41 references, 6 figures, 3 tables.
During sulfur vulcanization accelerated by guanidines (OTBG, DPG, DOTG) isothiocyanates (ITC) are formed inevitably. ITC are obtained both by splitting of thiourea originated from guanidines and by reaction of primary amines with CS2 (COS) donating compounds. The mechanism of the ITC formation was studied on unfilled IR compounds vulcanized at 180 and 210°C. The reaction products were analysed by GC/MS and HPLC/MS. Increasing sulfur dosage and higher vulcanization temperature promote the emission of ITC. Among the guanidines the highest amount of ITC is formed with OTBG. By addition of thiurams to the guanidine mixtures the amount of ITC increases frequently. Against that, MBT as secondary accelerator causes a retarding effect. Especially with OTBG/MBT-mixtures the lowest amounts of ITC are reached. Therefore small changes to either formulation or processing conditions can significantly reduce ITC in fumes.
Nonpolar compounds associate with organic carbon in the environment. The interaction between pollutants and dissolved organic carbon in natural waters is not as well defined as that between pollutants and sedimentary organic matter. The limitations of experimental techniques and extraction and concentration procedures are partially responsible for the incomplete description of pollutant-DOC (dissolved organic carbon) interactions. Despite the lack of complete understanding of the phenomenon, the association of nonpolar compounds with natural DOC can exert a significant influence on their environmental partitioning. Mathematical models of environmental behavior should include dissolved organic carbon in both overlying and sedimentary interstitial waters as compartments for equilibrium partitioning.
The purpose of this research is to determine the conditions whereby a new tire can be artificially aged in an accelerated manner, in order to duplicate the actual mechanism of chemical aging observed in field-aged tires. The ultimate goal of the study is to age tires to a desired level, say equivalent to 4 years old, and then test the tires in durability, high speed, and performance tests. The previous paper described various oven aging methodologies and the data analysis techniques used. This paper will build on the previously described data analysis techniques developed for elongation at break measurements and apply them to swelling ratio data and peel strength data. By utilizing the method initially developed by Gillen and modified by this laboratory for use with tires, it has been shown that the skim rubber of tires oxidatively ages at oven temperatures between 40 degrees C and 70 degrees C when mounted and inflated with either air or a blend of 50/50 N-2/O-2. The methodology has been successfully extended from elongation at break data to peel strength and swelling ratio data. The calculation of the Arrhenius activation energy for diffusion of oxygen through new and aged rubber was also determined. The effect of aging on permeability is to reduce the permeability of oxygen and increase the activation energy. These results have important implications when attempting to model the diffusional aging characteristics of inflated tires. The effect of changing the partial pressure of oxygen and its concomitant effect on the acceleration of aging was also investigated. The results indicate that by doubling the partial pressure of oxygen, the rate of oxidation is increased by approximately 1.5 times. This result is entirely consistent with the theory of diffusion limited oxidation(1).
Ciprofloxacin, griseofulvin, and rifampicin are three human antibiotics that are also widely used in the shrimp culture of Cangio coastal wetland (Vietnam, 10 degrees 24' 38" N, 106 degrees 57' 17" E). They have been detected in shrimp larvae pond and receiving water bodies. However, the environmental fate of these antibiotics in coastal wetland milieu is currently unknown. The aim of this study was to determine the degradation potential of these antibiotics in water and sediments from Cangio coastal wetlands. The effects of light, microbial activities, and presence of sediments on the degradation of all three antibiotics were investigated in "water-only" and "water-sediment" experiments. Results indicate that the environmental fate of those antibiotics was quite complex. Photodegradation seemed to play a major role in "water-only" system, since shorter t(1/2) was observed for ciprofloxacin, griseofulvin, and rifampicin, with light than in the dark, for both sterile and non-sterile conditions. Biodegradation played a minor role in the disappearance of the antibiotics and was overlaid by photodegradation. In addition, sorption to sediment was of major importance for antibiotics, especially for ciprofloxacin and rifampicin. The t(1/2) of these antibiotics in aqueous phase of "water-sediment" system was higher than for "water-only" experiments, indicating that a part of antibiotics were adsorbed by sediment. The biodegradation did not play a major role on sediment sorption of CIP and RIF, since no statistically significant differences between non-sterile and sterile conditions were observed. Only for GRI, the impact of the biodegradation to the sediment sorption could be found and led to the weak affinity to sediment sorption of this antibiotic. All three antibiotics were more sensitive to photodegradation than to biodegradation; however, the degradation rate was low. In addition, the sorption by sediment occurred also with a slow rate, so these antibiotics could recalcitrant persist in the coastal wetland environment.
The kinetics of aging of key tire properties both in the field and in oven exposures at different temperatures has been interpreted by using a combination of empirical models and accelerated shift factors. Crosslink density and rubber modulus increase with aging while peel strength and elongation-to-break decrease. In the case of oven aging, the rate of property change increases from 40 degrees C to 70 degrees C and then decreases. In the case of field aging, the rate of property change is greatest in hotter climates such as Phoenix and is slower in cooler climates such as Detroit. Spare tires age at a rate that is similar to 70% as fast as on-road tires. Below 70 degrees C, the rate data for all of the aging changes can be fit to an Arrenhius relationship with an activation energy of similar to 69 kJ/mole, a value that is consistent with the aging process resulting from diffusion limited oxidation. The measured acceleration factor of oven aging at 70 degrees C relative to on-road aging in Phoenix is independent of the property change measured confirming that it is possible to chemically age tires in ovens. It takes 67 weeks of oven aging at 70 degrees C to produce a tire that is aged 4 years in Phoenix. Field results show that the rate of tire aging varies by over a factor of 5 for the different tire types and brands studied in this work. The implications for tire durability testing are discussed.
The purpose of this research is to determine the conditions whereby a new tire can be artificially aged in an accelerated manner, in order to duplicate the actual mechanism of chemical aging observed in field-aged tires. The ultimate goal of the study is to age tires to a desired level, say equivalent to 4 years old, and then test the tires in various durability, high speed and performance tests. The first step was to determine the aging characteristics of field-aged tires, which has been the subject of another paper. 1 For this work, tires were statically aged in ovens. Tires were mounted, inflated, then oven aged continuously at temperatures ranging from 40 °C to 100 °C for various periods of times (from 2 weeks to 12 weeks). Both air and a 50/50 blend of N 2/O 2 were used as the inflation media. The tires were then dissected and analyzed for tensile and elongation properties of the rubber at the end of the steel belts. The results show that as the temperature was increased from 40 °C to 70 °C, the property degradation of the steel belt rubber accelerated. Shift factors were determined based on time-temperature superposition and the results analyzed by using the Arrhenius methodology. The oven results were similar to the field data, meaning the chemical aging mechanism was the same for both. As the oven temperature increased above 70 °C, degradation reactions began to dominate and the apparent aging mechanism changed.
One concern for recycle and reuse of scrap tires is the leaching of tire constituents (organic and inorganic) with time, and their subsequent potential harmful impacts in environment. The main objective of this study was to examine the leaching of dissolved organic carbon (DOC), dissolved nitrogen (DN), and selected inorganic constituents from scrap tires. Different sizes of tire chips and crumb rubber were exposed to leaching solutions with pH's ranging from 3.0 to 10.0 for 28days. The leaching of DOC and DN were found to be higher for smaller size tire chips; however, the leaching of inorganic constituents was independent of the size. In general, basic pH conditions increased the leaching of DOC and DN, whereas acidic pH conditions led to elevated concentrations of metals. Leaching was minimal around the neutral pH values for all the monitored parameters. Analysis of the leaching rates showed that components associated with the rubbery portion of the tires (DOC, DN, zinc, calcium, magnesium, etc.) exhibited an initial rapid followed by a slow release. On the other hand, a constant rate of leaching was observed for iron and manganese, which are attributed to the metal wires present inside the tires. Although the total amounts that leached varied, the observed leaching rates were similar for all tire chip sizes and leaching solutions. Operation under neutral pH conditions, use of larger size tire chips, prewashing of tires, and removal of metal wires prior to application will reduce the impact of tire recycle and reuse.
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In the reported experiments, the ozonation products of a common rubber antiozonant, N-(1,3-dimethyl-butyl)-N'-phenyl-p-phenylenediamine (HPPD), have been separated by liquid chromatography and identified by mass spectrometry. Three principal mechanisms appear to govern the ozonation of HPPD. Amine oxide formation leads to observed nitrosoaryl and nitroaryl products. Side-chain oxidation lead to several low molecular weight products, including some that contain an amide moiety. Nitroxide radical formation leads to a nitrone that is the most abundant ozonation product; a dinitrone is also formed. Ozonation of HPPD occurs mainly with degradation of the alkyl portion of the molecule. The results of this study are consistent with a combined ″scavenger-protective film″ theory of antiozonant protection of rubber compounds.
Previous studies revealed large differences in the transformation of pharmaceuticals in rivers with similar characteristics. The present work aimed at answering the question whether these differences are related to the transformation capacity of the specific river sediments. More generally, we also aimed at evaluating the overall diagnostic power of water/sediment tests. Incubation experiments with 9 pharmaceuticals were carried out with sediments sampled from three rivers. All compounds expect carbamazepine were removed at dissipation half-lives between 2.5 and 56 days; biotransformation was identified as the major removal process. Interestingly, sediment from river Roter Main was more efficient in removing pharmaceuticals than sediment from river Gründlach, while the opposite pattern was observed in previous field studies. Obviously, the physical boundary conditions are governing the actual elimination of pharmaceuticals and not the transformation potential of the specific sediments. In a separate experiment, an immediate onset of transformation was observed after introducing oxygen to an anoxic water/sediment system. Transformation rates in sediments sampled from several sites within one river varied up to a factor of 2.5. This considerable in-stream variability is a critical factor for environmental risk assessment where single cutoff values are being used for evaluating a compound's persistence.
In developing countries, wastes are usually not separated before being disposed of in solid-waste landfills, most of which are open dumps without adequate measures to prevent environmental pollution. To understand the leaching behavior of brominated flame retardants (BFRs) from waste consumer products in landfills, we have been conducting a long-term landfill lysimeter experiment since 2006 under conditions designed to mimic three types of landfill conditions in developing countries: aerobic, semi-aerobic, and anaerobic. Pilot-scale lysimeters (60-cm i.d.) were filled with a 400-cm layer of mixed wastes consisting of 35wt% food, 20wt% paper, 20wt% paper pulp, 13wt% plastic, 10wt% wood chips, 1wt% glass, and 1wt% metals, proportions that are typical of unsorted municipal solid waste in Asian developing countries. In the present study, we determined the concentrations of polybrominated diphenyl ethers, tetrabromobisphenol A, tribromophenols, and hexabromocyclododecanes in leachate samples collected from the lysimeters during the first 3.5years of the experiment, to evaluate BFR elution behavior in early-stage landfills. Under all three conditions, BFR elution started at the beginning of the experiment. The BFR concentrations in the leachates from the aerobic lysimeter tended to be lower than those from the anaerobic lysimeter, suggesting that the presence of air inside landfills considerably reduces BFR elution to the surrounding environment. During the 3.5-year experiment, BFR outflow from the lysimeters was only 0.001-0.58% of the total BFRs in the loaded waste; that is, most of the BFRs in the waste remained in the lysimeters.
Current concerns about the environmental safety of coal combustion fly ash have motivated this evaluation of the impact of fly ash use as a cement replacement in concrete materials on the leaching of constituents of potential concern. The chemical effects of fly ash on leaching were determined through characterization of liquid-solid partitioning using EPA Method 1313 for four fly ash materials as well as concrete and microconcrete materials containing 0% (control materials), 25% and 45% replacement of portland cement with the fly ash source. All source materials, concrete formulations and replacement levels are representative of US concrete industry practices. Eluate concentrations as a function of pH were compared to a broader range of available testing results for international concretes and mortars for which the leaching characteristics of the component fly ashes were unknown. The chemistry of the hydrated cement fraction was found to dominate the liquid-solid partitioning resulting in reduced leaching concentrations of most trace metals compared to concentrations from fly ash materials alone. Compared to controls, eluate concentrations of Sb, As, B, Cr, Mo, Se, Tl and V from concrete products containing fly ash were essentially the same as the eluate concentrations from control materials produced without fly ash replacement indicating little to no significant impact on aqueous partitioning.
The bioaccessibility of Zn in tire wear particles (TWP) has been studied in incubations in the presence of estuarine sediment and solutions that mimic the digestive chemistry of sediment-ingesting invertebrates. Sea water solutions of the protein bovine serum albumin (BSA), a surrogate for digestive amino acids, released about 2 % of total Zn from sediment–TWP preparations (in ratios of 100:1, 12:1 and 6:1) after a 5-h period. Although sodium taurocholate, a surrogate of digestive surfactancy, released quantities of Zn that were not always greater than those released by a sea water control, addition of taurocholate to BSA in sea water enhanced Zn release by solutions of the protein alone. Time courses of Zn release by BSA, with or without taurocholate, conformed to a diffusion-controlled reaction, with rate constants ranging from about 0.1 to 2 mg L−1 h−1/2. Results of the study suggest that sediment-ingesting invertebrates inhabiting coastal environments impacted by urban runoff are instrumental to the mobilisation of Zn.
The Standard Leaching Test (SLT) is drafted in order to make an estimate of the metal emission from metal contaminated waste-materials. A modification of SLT is developed and tested for research of the leaching behaviour of hydrophobic organic compounds. It encompasses the leaching procedure, treatment and enrichment of the percolate fractions. A cartridge sampling technique is described for the collection of polycyclic aromatic hydrocarbons (PAH) from the percolates. The modified SLT is applied succesfully on two environmental samples, polluted with PAH. Data from the SLT are used to classify waste materials according to Dutch governmental regulations dealing with re-use and landfilling.
A leaching test procedure for granular waste materials has been developed by a Nordic expert group. The Dutch leaching test procedure, especially the column test, was chosen as a starting point, as it best fullfilled the requirements for a leaching test. Furthermore, critical test parameters in the performance of the leaching tests are discussed. The following test procedure is recommended as a Nordic leaching test procedure for granular waste materials, especially ashes and slags from energy production: (1) a column test to LS 1–2, which gives information on the composition and variations in first leachates that appears in a landfill; (2) a batch leaching test with two or possibly three leaching steps (LS 2, LS 10 cumulative and possible LS 50 cumulative), which gives a rough estimate of the leached amounts and the leaching behaviour on a landfill, and also an estimate of the long-term leaching. This test is also recommended for routine testing and for small waste amounts; (3) especially for screening: an availability test (LS 200) which gives information on the totally leachable amounts in extreme test conditions.
Impacts of surface runoff to aquatic species are an ongoing area of concern. Tire and road wear particles (TRWP) are a constituent of runoff, and determining accurate TRWP concentrations in sediment is necessary in order to evaluate the likelihood that these particles present a risk to the aquatic environment. TRWP consist of approximately equal mass fractions of tire tread rubber and road surface mineral encrustations. Sampling was completed in the Seine (France), Chesapeake (U.S.), and Yodo-Lake Biwa (Japan) watersheds to quantify TRWP in the surficial sediment of watersheds characterized by a wide diversity of population densities and land uses. By using a novel quantitative pyrolysis-GC/MS analysis for rubber polymer, we detected TRWP in 97% of the 149 sediment samples collected. The mean concentrations of TRWP were 4500 (n = 49; range = 62-11 600), 910 (n = 50; range = 50-4400) and 770 (n = 50; range = 26-4600) μg/g d.w. for the characterized portions of the Seine, Chesapeake and Yodo-Lake Biwa watersheds, respectively. A subset of samples from the watersheds (n = 45) was pooled to evaluate TRWP metals, grain size and organic carbon correlations by principal components analysis (PCA), which indicated that four components explain 90% of the variance. The PCA components appeared to correspond to (1) metal alloys possibly from brake wear (primarily Cu, Pb, Zn), (2) crustal minerals (primarily Al, V, Fe), (3) metals mediated by microbial immobilization (primarily Co, Mn, Fe with TOC), and (4) TRWP and other particulate deposition (primarily TRWP with grain size and TOC). This study should provide useful information for assessing potential aquatic effects related to tire service life.
The chemical product diaryl-p-phenylene diamine (DAPD), produced by The Goodyear Tire & Rubber Company as POLYSTAY 100® (CAS 68953-84-4), is employed as an antidegradant in polymers used in tires and industrial rubber products. Previous evaluations pertaining to the ecological fate of DAPD indicated a lack of biodegradative activity in aquatic media. In order to further pursue the biodegradation potential of DAPD, it was deemed necessary to enhance the sensitivity of the aquatic biodegradation assay through (a) employment of a radiotracer of the test substance, and (b) optimisation of conditions for achieving maximal solubilisation of test material in the aquatic media of the incubation vessels. Test vessels were prepared according to the OECD ready biodegradability test guidelines, with DAPD added on silica gel at concentrations of 10 or 100μgL(-1), together with a surfactant to aid solubilisation. After 63d incubation up to 37% mineralisation was measured and up to 29% of the applied radioactivity was incorporated into cell biomass. Also, after 28d no DAPD could be measured in solution by radio-TLC and HPLC-MS. These three results demonstrate that the antioxidant DAPD undergoes microbiologically mediated biodegradation and is highly unlikely to persist in the environment.
This paper is directed to air pollution scientists interested in special mobile emission sources. The purpose was to determine the contribution which automobile tires make to air pollution. The gaseous hydrocarbon and sulfur compounds emitted in laboratory tests were identified. Although these hydrocarbons can participate in smog reactions, their mass emission rate is less than 0.1 % of the current exhaust hydrocarbon emission rate. Hydrocarbons from tires are not measurable near a freeway. The particulate emitted from tires ranges in size from 0.01 μm to more than 30 μm, with the larger particles dominating the total mass. Measurements along a California freeway showed that most of the tire debris had settled within 5 m of the pavement edge. Airborne rubber concentrations were less than 0.5 μg/m, or less than 5% of the total tire wear. These field measurements confirm the indoor emission pattern and verify that tire wear products are not a significant air pollution problem.
The OECD 308 water-sediment transformation test has been routinely conducted in Phase II Tier A testing of the environmental risk assessment (ERA) for all human pharmaceutical marketing authorization applications in Europe since finalization of Environmental Medicines Agency (EMA) ERA guidance in June 2006. In addition to the 'Ready Biodegradation' test, it is the only transformation test for the aquatic/sediment compartment that supports the classification of the drug substance for its potential persistence in the environment and characterizes the fate of the test material in a water-sediment environment. Presented is an overview of 31 OECD 308 studies conducted by 4 companies with a focus on how pharmaceuticals behave in these water-sediment systems. The geometric mean (gm) parent total system half-life for the 31 pharmaceuticals was 30 days with 10(th) / 90(th) percentile (10/90%ile) of 14.0/ 121.6 days respectively, with cationic substances having an half-life about 2 times that of neutral and anionic substances. The formation of non-extractable residues was considerable, with gm (10/90%ile) of 38% (20.5/81.4) of the applied radioactivity: cationic substances 50.8% (27.7/87.6), neutral substances 31.9% (15.3/52.3) and anionic substances 16.7% (9.5/30.6). In general, cationic substances had fewer transformation products and more unchanged parent remaining at day 100 of the study. A review of whether a simplified one-point analysis could reasonably estimate the parent total system half-life showed that the total amount of parent remaining in the water and sediment extracts at day 100 followed first-order kinetics and that the theoretical half-life and the measured total system half-life values agreed to within a factor of 1.68. Recommendations from this 4 company collaboration addressed: 1) the need to develop a more relevant water-sediment transformation test reflecting the conditions of the discharge scenario more representative of human pharmaceuticals; 2) potential use of a one-point estimate of parent total system half-life in the EMA ERA screening phase of testing; 3) the need for a more consistent and transparent interpretation of the results from the transformation study; consistent use of terminology such as dissipation, transformation, depletion and degradation in describing their respective processes in the ERA; 4) use of the parent total system dissipation half-life in hazard classification schemes and in revising predicted environmental concentration in ERA; and 5) further research into cationic pharmaceuticals to assess whether their classification as such serves as a structural alert to high levels of non-extractable residues; and whether this results in reduced bioavailability of those residues. Integr Environ Assess Manag © 2013 SETAC.
Log–log plots of measured organic carbon-normalized sediment pore-water distribution coefficients (K′OCS) for several polycyclic aromatic hydrocarbons (PAHs) versus their octanol-water partition coefficients (K′owS) at two sites in the Elizabeth River, Virginia, show large deviations from linearity. Organic-carbon normalized distribution coefficients for these PAHs between sediments and pore waters decreased by more than two orders of magnitude with depth as well. To determine to what extent pore water dissolved and colloidal organic carbon (DOC) was responsible for the observed nonlinearity and decrease in K′OC, a three-phase model was used to estimate pore-water PAH-DOC binding coefficients (KDOC). Partitioning of PAHs to pore-water DOC (i.e., KDOC) enhances the observed “dissolved” phase PAH concentration, especially for high-Kow compounds, contributing to the nonlinearity in K′OC-Kow plots. However, our application of the three-phase partitioning model to these data indicate that, at most, pore-water PAH-DOC binding accounts for one order of magnitude of the observed decrease in K′OC with depth in the sediment bed. The results of this study are consistent with three-phase partitioning theory for hydrophobic organic compounds between sediment organic matter, pore-water DOC, and freely dissolved aqueous phases in natural systems.
Synthetic athletic tracks and turf areas for outdoor sporting grounds may release contaminants due to the chemical composition of some components. A primary example is that of zinc from re-used scrap tires (main constituent, styrene butadiene rubber, SBR) - that might be harmful to the environment. Thus methods for the risk assessment of those materials need to be developed. Laboratory leaching methods like batch and column tests are widely used to examine the soil-groundwater pathway. We tested several components for artificial sporting grounds with batch tests at a liquid-to-solid (LS) ratio of 2 L/kg and column tests with an LS up to 26.5 L/kg. We found a higher zinc release in the batch test eluates for all granules, ranging from 15 % higher to 687 % higher versus data from column tests for SBR granules. The accompanying parameters, especially the very high turbidity of a special ethylene propylene diene monomer rubber (EPDM), or thermoplastic elastomer (TPE) eluates, reflect the stronger mechanical stress of batch testing. This indicates that the batch test procedure might not be suitable for the risk assessment of synthetic sporting ground components. Column tests on the other hand represent field conditions more closely and allow for determination of the time dependent contaminants release.
Because tires contain approximately 1-2% zinc by weight, zinc leaching is an environmental concern associated with civil engineering applications of tire crumb rubber. An assessment of zinc leaching data from 14 studies in the published literature indicates that increasing zinc leaching is associated with lower pH and longer leaching times, but the data display a wide range of zinc concentrations, and do not address the effect of crumb rubber size or the dynamics of zinc leaching during flow through porous crumb rubber. The present study was undertaken to investigate the effect of crumb rubber size using the Synthetic Precipitation Leaching Procedure (SPLP), the effect of exposure time using quiescent batch leaching tests, and the dynamics of zinc leaching using column tests. Results indicate that zinc leaching from tire crumb rubber increases with smaller crumb rubber and longer exposure time. Results from SPLP and quiescent batch leaching tests are interpreted with a single-parameter leaching model that predicts a constant rate of zinc leaching up to 96 hr. Breakthrough curves from column tests displayed an initial pulse of elevated zinc concentration (~3 mg/L) before settling down to a steady-state value (~0.2 mg/L), and were modeled with the software package HYDRUS-1D. Washing crumb rubber reduces this initial pulse but does not change the steady-state value. No leaching experiment significantly reduced the reservoir of zinc in the crumb rubber.
Benzothiazole (BT), 2-hydroxybenzothiazole (HOBT), and 2-(4-morpholino)benzothiazole (24MoBT) leach from crumb rubber material (CRM) and asphalt containing 1−3% CRM. To determine whether benzothiazoles would be an environmental problem if roads containing CRM-modified asphalt (CMA) were built in the state of Rhode Island, the source and fate of these compounds were investigated. Benzothiazoles enter the environment from a number of sources such as the leaching of rubber products, fine particles of automobile tires, and antifreeze. Compared to the fluxes of benzothiazoles currently entering rivers from urban runoff, CMA roads may initially deliver substantially more benzothiazoles to the environment; however, with time this source may diminish as the road ages. Because the benzothiazoles are water soluble, it is unlikely that they will sorb to particles, settle to sediments, or be bioaccumulated. In addition, BT can be volatilized, and BT and HOBT can be microbially degraded. Therefore, the environmental chemistry of these compounds suggests that the inputs of benzothiazoles from CMA should not be harmful.
If precautions are taken to eliminate or account for nonsettling (or nonfilterable) microparticles or organic macromolecules that remain in the aqueous phase during laboratory sorption tests, the observed partition coefficients (Kp or Koc) for a group of model hydrophobic organic compounds (PCBs) are found to remain constant over a wide range of solid-to-solution ratios. Further, the partition coefficients for either sorptive uptake or desorptive release are indistinguishable and confirm the reversible nature of hydrophobic sorption. It is proposed that descriptions of the 'speciation' of hydrophobic compounds in natural waters should include not only dissolved and sorbed-to-sediment fractions but also a component sorbed to nonsettling microparticles or organic macromolecules.
More than 100 organic compounds are quantified in these samples, including n-alkanes, n-alkanoic acids, n-alkenoic acids, n-alkanals, n-alkanols, benozoic acids, benzaldehydes, polyalkylene glycol ethers, PAH, oxy-PAH, steranes, hopanes, natural resins and other compound classes. Paved road dust acts as a repository for vehicle-related particles, which can then be resuspended by the passing traffic. To evaluate the contributions from major urban sources to the road dust complex, source profiles representing different types of vehicle exhaust, brake dust, tire debris, and vegetative detritus are compared, and their fractional contributions are estimated using several groups of organic tracer compounds. -from Authors
The potential risk of toxic metals that could leach into a beach environment from plastic litter washed ashore on Ookushi Beach, Goto Islands, Japan was estimated by balloon aerial photography, in situ beach surveys, and leaching experiments in conjunction with a Fickian diffusion model analysis. Chromium (Cr), cadmium (Cd), tin (Sn), antimony (Sb), and lead (Pb) were detected in plastic litter collected during the beach surveys. Polyvinyl chloride (PVC) fishing floats contained the highest quantity of Pb. Balloon aerial photography in conjunction with a beach survey gave an estimated mass of Pb derived from plastic litter of 313 ± 247 g. Lead leaching experiments on collected PVC floats showed that Pb in the plastic litter could leach into surrounding water on the actual beach, and that plastic litter may act as a "transport vector" of toxic metals to the beach environment. Using the experimental data, the total mass of Pb that could leach from PVC plastic litter over a year onto Ookushi Beach was estimated as 0.6 ± 0.6 g/year, suggesting that toxic metals derived from plastic beach litter are a potential "pathway" to contamination of the beach environment due to their accumulation in beach soil over time.
The 6:2 FTOH [F(CF(2))(6)CH(2)CH(2)OH] is a major raw material being used to replace 8:2 FTOH [F(CF(2))(8)CH(2)CH(2)OH] to make FTOH-based products for industrial and consumer applications. A novel aerobic sediment experimental system containing 20g wet sediment and 30mL aqueous solution was developed to study 6:2 FTOH biotransformation in river sediment. 6:2 FTOH was dosed into the sediment to follow its biotransformation and to analyze transformation products over 100d. The primary 6:2 FTOH biotransformation in the aerobic sediment system was rapid (T(1/2)<2d). 5:3 acid [F(CF(2))(5)CH(2)CH(2)COOH] was observed as the predominant polyfluorinated acid on day 100 (22.4mol%), higher than the sum of perfluoropentanoic acid (10.4mol%), perfluorohexanoic acid (8.4mol%), and perfluorobutanoic acid (1.5mol%). Perfluoroheptanoic acid was not observed during 6:2 FTOH biotransformation. The 5:3 acid can be further degraded to 4:3 acid [F(CF(2))(4)CH(2)CH(2)COOH, 2.7mol%]. This suggests that microbes in the river sediment selectively degraded 6:2 FTOH more toward 5:3 and 4:3 acids compared with soil. Most of the observed 5:3 acid formed bound residues with sediment organic components and can only be quantitatively recovered by post-treatment with NaOH and ENVI-Carb™ carbon. The 6:2 FTCA [F(CF(2))(6)CH(2)COOH], 6:2 FTUCA [F(CF(2))(5)CF=CHCOOH], 5:2 ketone [F(CF(2))(5)C(O)CH(3)], and 5:2 sFTOH [F(CF(2))(5)CH(OH)CH(3)] were major transient intermediates during 6:2 FTOH biotransformation in the sediment system. These results suggest that if 6:2 FTOH or 6:2 FTOH-based materials were released to the river or marine sediment, poly- and per-fluorinated carboxylates could be produced.
A method was developed for the analysis of 2-substituted benzothiazoles from wastewaters by reversed-phase liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS). While benzothiazole (BT), 2-amino- (ABT), 2-methyl-, 2-thiocyanomethylthio- and 2-methylthiobenzothiazole were separated with a methanol gradient acidified with formic acid and detected in the positive mode, 2-mercapto- and 2-hydroxybenzothiazole (OHBT) as well as benzothiazole-2-sulfonic acid (BTSA) were separated with the addition of ammonium acetate and detected in the negative ion mode. Detection limits range from 10 ng L−1 for ABT to 200 ng L−1 for OHBT after direct injection of 100 µL sample volumes, while BT requires 2.5 µg L−1. The method is, thus, suitable for direct analysis in wastewaters. Its application to tannery effluent samples revealed, that, besides a 90–95% elimination of total benzothiazoles, the concentration of OHBT and BTSA increased during the biological treatment. Copyright © 2000 John Wiley & Sons, Ltd.
In this chapter, the wastes to be tested for their ecotoxicological response by exposing them to the eluate as obtained from
EN 14735 are characterized in greater detail by the leaching tests developed in CEN/TC292/WG 6 (pH dependence leaching tests
TS 14429 and percolation test TS 14405). These methods allow chemical speciation modeling, which provides information on the
“free” forms of inorganic and organic substances in solution as opposed to dissolved organic carbon (DOC) associated and colloid
bound forms. The unbound form of the substances is considered bioavailable and thus responsible for the observed response.
In addition, the repartitioning of substances between bound and unbound forms as a result of the dilution of the eluate with
a medium to quantify the ecotoxicological response can be modeled; it has been shown not to be a simple dilution factor as
the relative concentration of the “free” forms increased upon dilution. The combination of more detailed leach testing and
ecotoxicological studies provided the basis for a more detailed evaluation of ecotoxicological response than was possible
earlier.
KeywordsLeaching-Chemical speciation-Waste characterization-Bioavailability
In recent years leaching tests for construction materials and wastes have been developed with the emphasis on using them as prediction tools for release in the long term rather than as arbitrary pass/fail tests. In the first stages of development, the mechanisms of release and release-controlling parameters have been assessed. For each of these aspects leaching tests have been selected, developed and in part standardized. Not all relevant aspects of leaching are yet covered. The reducing properties of materials, for example, are still not taken into account properly. The need for these more elaborate tests is increasing as the policy of re-using waste materials in construction is expanding. As a consequence, the desire to improve material quality is increasing. For this purpose more detailed knowledge on the chemical speciation of contaminants is needed, as a treatment of waste carried out to reduce a few contaminants with too high leach rates may lead to an undesired increase in the release of other contaminants, which were previously not a problem. This requires a more integral approach and a good understanding of the consequences of changes in material properties. Tests focused on two main aspects of leaching can be identified: (1) release as a function of time; (2) release as a function of main leaching controlling parameters, such as pH, redox and complexation. The relation between these tests and the data interpretation associated with them is discussed. Another distinction in the use of tests is related to the level of understanding needed. In CEN TC 292 tests have been distinguished as: characterization tests, compliance tests, and on-site verification tests. An important aspect of the new development of tests with release prediction capabilities is the verification of such predictions in the field. An example of the relation between predictions of release from laboratory test data and field observations is presented: release from MSWI bottom ash monofills. Finally, recent developments in the EC DGXII Standard, Measurements & Testing Programme and CEN TC 292 Characterization of Wastes are addressed.
The purpose of this study was to characterize the physical and chemical properties of particles generated from the interaction of tires and road surfaces. Morphology, size distribution, and chemical composition were compared between particles generated using different methods, including on-road collection, laboratory generation under simulated driving conditions, and cryogenic breaking of tread rubber. Both on-road collected and laboratory generated particles exhibited the elongated shape typical of tire wear particles, whereas tread particles were more angular. Despite similar morphology for the on-road collected and the laboratory generated particles, the former were smaller on average. It is not clear at this stage if the difference is significant to the physical and chemical behavior of the particles. The chemical composition of the particles differed, with on-road generated particles containing chemical contributions from sources other than tires, such as pavement or particulates generated from other traffic-related sources. Understanding the differences between these particles is essential in apportioning contaminant contributions to the environment between tires, roadways, and other sources, and evaluating the representativeness of toxicity studies using different types of particulate generated.
A laboratory study was conducted to determine if automobile tires immersed in fresh water leach chemicals which are toxic to aquatic biota. Three tire types were examined - tires obtained from a floating tire breakwater; road-worn tires from the same vehicle; and new tires. Whole tires were immersed in 300 L of water (natural groundwater) and subsamples (40 L) of water were removed at 5, 10, 20 and 40 d for use in acute static lethality tests. Overlying water from both new and used tires was lethal to rainbow trout (Oncorhynchus mykiss) but leachate from used tires was more toxic (96-h LC50s - 11.8 to 19.3 %v/v) than leachate from new tires (96-h LC50s - 52.1 to 80.4 %v/v). In addition, leachate remained relatively toxic to rainbow trout over time (8 d for new and 32 d for used) after tires were removed from the aquaria indicating that the chemicals responsible for toxicity degrade slowly and are non-volatile. No toxicity to cladocerans (Daphnia magna; 48-h exposure) or fathead minnows (Pimephales promelas; 96-h exposure to leachate from 20 and 40 d only) was observed with these same leachates. Tires from a floating tire breakwater which had been installed for several (10) years did not release chemicals which were toxic to any species tested. In separate experiments, concentrated (10X) leachate from tires immersed for 25 d in water inhibited bioluminescence in the marine bacterium, Photobacterium phosphoreum, (Microtox™ test), the enzyme, β-galactosidase, in mutant Escherichia coli (ToxiChromo™ Test) and the enzyme, NADH-coenzyme Q reductase, in the inner membrane of mitochondria (beef heart submitochrondria particle test). Several other screening tests (e.g., nematode lethality/mutagenicity test; bacterium (Spirillum volutans) motility inhibition test and the SOS-Chromotest with and without S-9 activation) were not sensitive to tire leachates. Further studies to identify the toxic compounds and to determne the extent of toxicity under field conditions of dilution are necessary.
Numerous ecological risk assessment methodologies have been developed over the last twenty years around the world for evaluating urban and industrial systems and installations, by both the organisations responsible for implementing regulations and the scientific community. Although these methodologies share the general principle underlying their use, they differ widely with respect to the approaches chosen and the resources employed to apply them. Also, they may even have different objectives: prior assessment as part of an impact study before building a new installation, or retrospective assessment, for example, in view to explaining the reasons for an impact recorded or for forecasting additional expected impacts. This article provides a synthesis of the different approaches used around the world for carrying out each of the major steps common to all ecological risk assessment methodologies. The advantages and limitations of these different options are discussed in order to provide elements for formulating any new methodology adapted to a given scenario. To conclude, perspectives for improving the tools required for these methodologies are proposed, and the research works to which priority should be given are identified.
Correctly predicting the leaching potential of arsenic (As) and selenium (Se) is critical for assessing the environmental impact of coal fly ash. This study investigated the impacts of several key environmental factors, including pH, leaching time, and ash washing on the batch leaching behavior of As and Se from bituminous coal fly ashes. The experimental results demonstrated that As and Se leaching from fly ash increased beyond the minimal leaching pH ranges. Increasing leaching time increased As leaching but decreased Se leaching in the alkaline pH condition. A speciation-based adsorption model was used to quantify the batch leaching data, and determine the intrinsic leaching parameters including the total batch leachable mass and the adsorption constant of As or Se. The modeling approach was validated by correctly predicting the independent batch leaching data in a broad pH range and a different L/S condition. Experimental and modeling results also demonstrated that ash washing and ash aging (longer leaching time) did not change the adsorption constants of As and Se on the ash surface. However, ash washing could increase the availability of As and Se for leaching.
Tire wear particles (TWP) abraded from end-of-life passenger car tires have been added at a concentration of 1 g L⁻¹ to river water, sea water and mixtures thereof in order to examine the chemical controls on the leaching of Zn from the rubber matrix. Results of time-dependent experiments conducted over a period of 5 days were consistent with a diffusion controlled leaching mechanism with rate constants of about 0.04 mg L⁻¹ h⁻½ in river water and between about 0.02 and 0.03 mg L⁻¹ h⁻½ in sea water. Additional experiments revealed a reduction in Zn dissolution with both increasing salinity and pH and enhancement of leaching in the presence of fluorescent light compared with dark conditions. In corresponding experiments conducted in the presence of a fixed quantity (0.8 g L⁻¹) of clean, fractionated estuarine sediment, aqueous Zn concentrations were reduced by at least an order of magnitude. Increasing the quantity of sediment resulted in a progressive reduction in Zn concentration until an apparent equilibrium was achieved, with partition coefficients defining the sediment-water distribution of Zn of about 550 mL g⁻¹ and 270 mL g⁻¹ in river water and sea water, respectively. Results are interpreted in terms of the dissolution of ZnO and other residual complexes from the matrix and the subsequent, rapid adsorption of Zn²⁺ ions to coexistent estuarine sediment. The findings of the study are discussed in terms of their implications for the transport, fate and effects of TWP Zn in aquatic environments that are likely to receive urban runoff.
The evaluation of the hazardous nature of a waste is frequently based on total composition in many jurisdictions, while for most cases the chemical form of the constituents and the release pathways that may result in exposure of man and organisms under conditions of handling, transport, disposal or beneficial use are the most important factors controlling potential environmental impact. Thus, leaching assessment related to possible management scenarios rather than total content can provide a much more robust basis for evaluating health risks and environmental risks for waterborne pathways. Standardized characterisation leaching tests based on intrinsic characteristics of a material provide a new foundation for needed decisions. Chemical speciation modelling using characterisation testing results provides a means to identify mechanisms controlling constituent release, including mineral or sorptive phases, and thus insights into the long-term release behaviour of the material and approaches to reducing potential impacts.
Rates of pesticide degradation in aquatic ecosystems often differ between those observed within laboratory studies and field trials. Under field conditions, a number of additional processes may well have a significant role, yet are excluded from standard laboratory studies, for example, metabolism by aquatic plants, phytoplankton, and periphyton. These constituents of natural aquatic ecosystems have been shown to be capable of metabolizing a range of crop protection products. Here we report the rate of degradation of six crop protection products assessed in parallel in three systems, under reproducible, defined laboratory conditions, designed to compare aquatic sediment systems which exclude macrophytes and algae against those in which macrophytes and/or algae are included. All three systems remained as close as possible to the Organisation for Economic Co-operation and Development (OECD) 308 guidelines, assessing degradation of parent compound in the total system in mass balanced studies using ((14) C) labeled compounds. We observed, in all cases where estimated, significant increases in the rate of degradation in both the algae and macrophyte systems when compared to the standard systems. By assessing total system degradation within closed, mass balanced studies, we have shown that rates of degradation are enhanced in water/sediment systems that include macrophytes and algae. The contribution of these communities should therefore be considered if the aquatic fate of pesticides is to be fully understood.
In 2006, the European Union (EU) promulgated a monumental regulatory initiative for the Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH). To date, several thousand pages of text have been needed to describe the expectations of this regulation. There were numerous reasons for the promulgation of REACH, but, by and large, it is an extension of the global desire to produce fewer industrial chemicals, to understand the possible human and ecological hazards of those that are produced, and to insure that any major threat is anticipated, as well as prevented. Most industry-related groups consider it the most wide-ranging and costly regulatory initiatives related to health risk assessment ever to be promulgated. This review presents a description of REACH that should inform scientists, managers, and others about its objectives and the means to satisfy them. Registration is required for all chemicals manufactured or imported into the EU, unless specifically exempted. Registration is expected to be a collaborative process among companies, which will generate a dossier containing data on physicochemical characteristics, as well as toxicological and ecotoxicological properties. Though the magnitude of the gaps in the data required for registration is uncertain at this point, it is clear that basic toxicology testing will have to be conducted for many chemical substances that have not undergone formal review up to this point. For many chemicals, an examination of hazards and risks arising from the use of these substances will also be required in the form of a chemical safety report (CSR). Beginning with the dual processes of dossier and substance evaluation, the European Chemicals Agency (ECHA), the Member States of the EU, and the European Commission will identify chemicals that may pose unacceptable hazards to human health and/or the environment, and will curtail or restrict their usage. The implementation of REACH will expand and deepen the fields of applied toxicology and exposure assessment by spurring activity and innovation in sampling and analysis, toxicology testing, exposure modeling, alternative toxicity testing, and risk assessment practices.
Leaching tests are becoming more relevant in assessing solid waste material, particularly with respect to groundwater risks. In the field, water infiltration is the dominant leaching mechanism, which is simulated in the lab with batch and column tests. In this study, we compared percolation, through analytical solutions of the advection-dispersion equation, to laboratory batch and sequential leaching tests. The analytical solutions are supported with comprehensive data from various field and laboratory leaching of different solutes from waste materials and soils collected in long-term joint research projects funded by the German Federal Ministry for Education and Research and the Federal Environment Agency. The comparison of theory and data is facilitated if concentrations and cumulative release are plotted versus the liquid-solid ratios (LS). Both theory and data indicate that leaching behaviour is independent of duration and physical dimensions of the leaching tests. This holds even if field lysimeters are compared to laboratory columns of different size, different flow velocities as well as different contact times. In general, laboratory batch tests over predict effluent concentrations (for LS<K(d)). Leaching of solutes from solid samples of certain materials (e.g. chloride from incineration ashes or sulphate from demolition waste) in column and lysimeter tests compares very well and agrees with the analytical solutions. Overall, reproducibility and agreement with theory of column tests are better than batch tests, presumably because the latter are prone to artefacts (e.g. in liquid-solid separation steps). Theory and data fit surprisingly well, despite the fact that the theory is based on the local equilibrium assumption; non-linear sorption and chemical reactions in the solid waste materials are not considered.
In order to determine whether shredded rubber mulches (RM) pose water quality risks when used in stormwater best management practices (BMPs) such as bioretention basins, batch leaching tests were conducted to identify and quantify constituents in leachates from RM such as metal ions, nutrients, total organic carbon (TOC), and aryl hydrocarbon receptor (AhR) activity (determined by the chemically activated luciferase gene expression (CALUX) bioassay) at varied temperature and initial pH values. The results indicate that aqueous extracts of RM contain high concentrations of zinc (Zn) compared with wood mulches (WM), and its concentration increased at lower pH and higher temperature. Although methanol extracts of RM displayed high AhR activity, none of the aqueous extracts of RM had significant activity. Hence, while unknown constituents that have significant AhR activity are present in RM, they appear to be not measurably extracted by water under environmental conditions relevant for stormwater (5<pH<9, 10<T<40 degrees C). Our results suggest that organic constituents in water extracts of RM which have AhR activity may not be of significant concern while leaching of Zn from RM appears to be a potentially larger water quality issue for RM.
Highway runoff has the potential to negatively impact receiving systems including stormwater retention ponds where highway particulate matter can accumulate following runoff events. Tire wear particles, which contain about 1% Zn by mass, make up approximately one-third of the vehicle derived particulates in highway runoff and therefore may serve as a stressor to organisms utilizing retention ponds as habitat. In this study, we focused on the potential contribution of tire debris to Zn accumulation by Rana sylvatica larvae and possible lethal or sublethal impacts resulting from exposure to weathered tire debris during development. Eggs and larvae were exposed to aged sediments (containing either ZnCl2 or tire particulate matter, both providing nominal concentrations of 1000 mg Zn kg(-1)) through metamorphosis. Water column Zn was elevated in both the ZnCl2 and tire treatments relative to the control treatment, indicating that aging allowed Zn leaching from tire debris to occur. Tissue Zn was also elevated for the ZnCl2 and tire treatments indicating that Zn in the treatments was available for uptake by the amphibians. Exposure to both ZnCl2 and tire treatments increased the time for larvae to complete metamorphosis in comparison with controls. We also observed that the longer the organisms took to complete metamorphosis, the smaller their mass at metamorphosis. Our results indicate that Zn leached from aged tire debris is bioavailable to developing R. sylvatica larvae and that exposure to tire debris amended sediments can result in measurable physiological outcomes to wood frogs that may influence population dynamics.
In this study, we investigated the contents of several brominated compounds in TV molding plastics, as well as their leaching characteristics in the presence of DHM. The PBDE content was about 3% of the sample weight, and deca-BDE was the most abundant homologue, accounting for over 80% of the total amount. TBBPA, PBPs and PBBs content was 8100, 4700 and 250 ng/g, respectively. Despite no detection of most of the lower brominated DEs in distilled water, most homologues could be detected in DHM solution, and their solubility increased according to the contact time; those of highly brominated compounds increased to 10 times their maximum solubility in distilled water. Especially, contrary to the relatively faster equilibrium in distilled water, BFR solubility in DHM solution was maintained even after 20 days. In addition, a modified first-order model adequately reflected rapid desorption for each compound in the initial period, but slow desorption afterwards. From an overall perspective, it is clear that hydrophobic BFRs can leach out to a great extent in the presence of DHM, which is a matter of great concern in E&E waste as the potential contaminant source of BFRs, especially in landfills and open dump sites that provide the perfect conditions for exposure of BFRs to abundant DHM.