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Adsorption-desorption studies of metalaxyl in fifteen agricultural soil samples from Southern Portugal and Spain were performed following a batch equilibration method. Very high sorption was observed on a clay soil of high content in altered illite, but, when this soil was excluded from regression analysis, organic matter (OM) was the most importan...
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We tested the capacity of biochar (made at 450 °C from a common reed species) to neutralise pH and remove metals in two acid drainage waters (pH 2.6 and 4.6) using column leaching and batch mixing experiments. In the column experiments, the acid drainage water was neutralised upon passage through the biochar with substantial increases (4-5 pH units...
Citations
... Soil containing organic amendments, and their hydrosoluble fraction, play an important factor on pesticide dissipation, affecting their adsorption and transport processes through various chemical interactions. 34,43,44,45,46,47 Although in most cases, addition of organic amendments increases sorption, leaching of the pesticides can be either reduced or promoted. On the contrary, organic matter content might enhance the retardation of organic pollutants through different coating processes such as cumulative sorption or cosorption. ...
The dissipation and side-effect of metribuzin (MBZ) were studied with various factors; two soil types (clay loam and sandy loam), soil amendment (wheat straw and without amendment), two temperature levels (25 and 50°C), sterilization (sterilized and unsterilized soil) and time of incubation (15 and 30 days) and designed by Windows version of MINITAB software package to reduce the time and the cost as well as increased the precision. Determination of MBZ by HPLC with recoveries ranged from 50.85 to 108.09%. The MBZ residues were detected in all samples up to 60 days of storage, respectively with decline in their concentrations with the time of incubation. The clay loam soil showed higher dissipation than the sandy loam soil. The different factors in the present study confirmed that the wheat straw amendment, non-sterilization and incubation at 50°C caused higher dissipation of MBZ than without wheat straw, sterilization and incubation at 25°C. The dissipation was described mathematically by a first order equation with t0.5 was ranged from 9.62 to 16.82 days in clay loam soil and from 10.01 to 16.04 days in sandy loam soil. The side-effect of MBZ was tested on soil dehydrogenase activity that can be considered as an indicator of the biological activity and microbial degradation. The result proved that the enzyme activity was significantly decreased in all treatments compared with the controls at 1 and 3 days of incubation then it was gradually increased at 7, 10, 15 and 30 days of incubation. Treatments of wheat straw, non-sterilized and incubated at 25°C or 50°C showed the lowest enzyme inhibition among all treatments.
... The adsorption of organic contaminants on clay minerals is affected by soil pH, because at neutral-alkaline values, they possess negative charges that favor the adsorption of cationic organic contaminants and contribute to electrostatic repulsions of anionic molecules [23,24]. In addition, soil texture is another parameter that influences the adsorption of CECs, because high percentages of clay minerals enhance the adsorption of CECs onto soils [25,26]. Iron, aluminum, and manganese oxyhydroxides have reactive oxygen functional groups and a high specific surface area that can help to adsorb CEC s , reducing their leaching into water or absorption by plants [27,28]. ...
Background
The irrigation with treated wastewaters can be a way for the introduction of organic contaminants in soils. However, their adsorption onto soils can allow a control of their bioavailability and leaching. The adsorption is influenced by properties of contaminants (water solubility, chemical structure) and soils (organic matter content, pH, mineralogy). This study aimed to investigate the effect of mineralogical composition, organic matter content and others parameters of soils on the adsorption of sulfamethoxazole (SMX) and diclofenac (DCF), two contaminants of emerging concerns (CECs), in real cases (Altamura, Sibari and Noci soils).
Results
The isotherms data showed that the adsorption of the two CECs closely matched the Freundlich model, even if the DCF could also fit the linear one. The only exception was the adsorption of SMX on the soil of Sibari, for which Langmuir's model fitted better. In all cases, the K d values were the highest for Altamura soil according mainly to its content of organic carbon. Positive correlations were found between K d value of DCF and the soil organic carbon and Al oxyhydroxides content, suggesting their roles in its adsorption, while SMX showed only a slight positive correlation with the soil organic carbon content. Finally, between the two CECs studied, DCF was more adsorbed than SMX also because of the lower water solubility of the former.
Conclusions
The good interaction between DCF and soil organic carbon suggests the organic amendment of soils before the application of treated watewaters. The low adsorption of SMX onto soils suggests greater leaching of this compound which is, therefore, potentially more dangerous than DCF. For this reason, the application of a filtration system with appropriate adsorbent materials before the application of wastewater to soils should be expected.
Graphical Abstract
... Overall hydrolyzable NERs and the extractable proportions after 10 d, as well as 92 d, were higher (irreversible) in the clay fraction than in the silt fraction (Fig. 5). According to other studies (Sukop and Cogger, 1992;Sukul and Spiteller, 2001;Fernandes et al., 2003;McAllister and Semple, 2010), metalaxyl has a preference for sorption to mineral surfaces. In particular, the interlamellar spaces of clay minerals, as well as diffusion of metalaxyl to cavities of microaggregates and organo-clay complexes, offer sites protected from enzymatic or microbial degradation; such residues are likely released to the environment under natural conditions. ...
... Binding constants based on Freundlich adsorption isotherms were highest in soils with high clay content with corresponding lowest mobility in such soils (Sharma and Awasthi, 1997). Similar results were reported by Fernandes et al. (2003), who compared 15 agricultural soils by performing batch equilibration studies. Besides the clay content, SOM was the most important soil property for metalaxyl sorption, which could even be enhanced when SOM was increased by organic amendments, such as biochar (Gámiz et al., 2016a). ...
The proportion of organic matter and mineral composition are important factors determining the formation and type of non-extractable residues (NERs) of pesticides in soil. In this study, we investigated the enantioselectivity in degradation and NER formation of the chiral fungicide metalaxyl in soil particle size fractions (silt and clay). Microbial and extracellular enzyme activities during these processes were monitored in incubation of silt and clay samples isolated from sterilized and non-sterilized soil samples collected from a long-term agricultural field experimental site in Ultuna, Sweden. The temporal influence on the fate of the fungicide was noted by short-term (10-d) and long-term (92-d) incubations. Besides the acquisition of quantitative data with gas chromatography-mass spectrometry (GC/MS), stereoselective analyses were performed with chiral GC/MS. Quantitative results pointed to a higher metabolism rate of the pesticide through microbial activity than through extracellular enzyme activity. This was also confirmed by the enantioselective depletion of R-metalaxyl and the subsequent formation of R-metalaxyl acid in microbially active samples from non-sterilized soil. The silt fraction containing a high amount of organic matter exhibited a significant hydrolyzable proportion of metalaxyl NERs that was releasable under alkaline conditions. On the contrary, the clay fraction showed an enhanced affinity for covalently bound residues. Based on our results, we recommend differentiating between reversibly and irreversibly bound proportions of pesticides in persistence and environmental risk assessment because the reversible fraction contained potentially bioavailable amounts of residues that may be released under natural conditions.
... Metalaxyl-M (methyl N-(2,6dimethylphenyl)-N-(methoxyacetyl)-D-alaninate)) is the biologically active R-enantiomer of the racemic compound metalaxyl. It is one of the most used fungicide worldwide and is highly persistent, mobile, and leachy in soil (Fernandes et al. 2003). Metribuzin (4-amino-6-tert-butyl-3methylsulfanyl-1,2,4-triazin-5-one) is a selective triazinone herbicide. ...
... Compared with unamended soil, the addition of CM and, especially, BC altered the distribution of this compound along the soil profile, counteracting its downward movement (Fig. 4a). Fernandes et al. (2003) reported that the adsorption of metalaxyl in soil was affected mainly by the organic fraction. The adsorption capacity of a CM-based biomixture for metalaxyl-M was much higher than that of the soil (Karanasios et al. 2010). ...
Hemp (Cannabis sativa L.) seedlings were used to remove from water the fungicide metalaxyl-M and the endocrine disruptor (EDC) bisphenol A (BPA) at concentrations ranging from 2 to 100 μg mL−1. In 7 days of exposure, despite the phytotoxicity of each compound that reduced elongation and biomass, the seedlings were able to remove between 67 and 94% of metalaxyl-M and between 86 and 95% of BPA. The amounts of metalaxyl-M and BPA extracted from plant dry biomass were in the range of 106–3861 μg g−1 and 16–101 μg g−1, respectively, and resulted positively correlated to both the dose of compound added (P ≤ 0.01) and the amount removed by the plants (P ≤ 0.01). Plant uptake and transformation were the main mechanisms involved in the removal of the compounds. In another set of experiments, hemp was used to remove a mixture of two pesticides, metalaxyl-M and metribuzin, and three EDCs, BPA, 17β-estradiol (E2), and 4-tert-octylphenol (OP), at concentrations of 10, 10, 10, 10, and 1 μg g−1, respectively, from soil column not added and added with 2.5% (w/w) of a green compost (CM) or a wood biochar (BC). In 25 days, plants did not alter considerably the distribution of the compounds along the soil profile and were capable of removing, on average, 12, 11, 10, 9, and 14% of metalaxyl-M, metribuzin, BPA, E2, and OP, respectively. During growth, hemp transformed the compounds and accumulated part of them (except OP) mainly in the shoots. CM and, especially, BC significantly protected the plants from the toxicity of the compounds and enhanced the retention of the latter in soil, contrasting leaching. Thus, the single or synergistic use of hemp and amendments deserves attention being a very low-cost and eco-sustainable strategy to remediate water and soil.
... The low metalaxyl adsorption in that soil was ascribed to its low organic C content which, in turn, would be generally responsible for the high product mobility and the consequent hazardousness for the environment (Bermúdez-Couso et al. 2011). Various authors reported that the adsorption of metalaxyl in soil depended mainly on the levels of soil OM and soil colloids, although some authors give more importance to the former property (Fernandes et al. 2003(Fernandes et al. , 2006Bermúdez-Couso et al. 2011) and others to the latter (Sharma and Awasthi 1997). To the best of our knowledge, no sorption kinetics studies of metalaxyl-M onto BC or VC are present in the literature. ...
... The K d value (1.27 L kg −1 ) obtained in our study for the non-amended soil was within the range of K d values (0.03-3.08 L kg −1 ) reported for soils by Bermúdez-Couso et al. (2011). The K d values of metalaxyl on a series of cultivated soils ranged between 0.64 and 1.76 L kg −1 (Fernandes et al. 2003). Such low sorption is related to the low hydrophobicity of metalaxyl-M. ...
... Although some researchers reported that the sorption of this fungicide was greatly affected by the clay content of soil (Sharma and Awasthi 1997), the role of soil OM cannot be questioned. The OM content is the main soil factor that controls metalaxyl adsorption, even if clay minerals may also play a relevant role in the process (Fernandes et al. 2003;Bermúdez-Couso et al. 2011). However, it is largely accepted that sorption of pesticides in soil is significantly influenced not only by the amount of OM present but, above all, by its nature, type and stability (Senesi and Loffredo 2018;Loffredo and Senesi, 2006). ...
This study aimed to investigate changes in metalaxyl-M sorption-desorption capacity of soil following the addition of two types of amendments. Two biochars (BC) from grapevine pruning residues (BC-G) and spruce wood (BC-S) and two vermicomposts (VC) obtained vermicomposting digestates from a mixture of manure and olive mill wastewater (VC-M) and buffalo manure (VC-B) were used. Using a batch equilibration method, the materials and a silt loam soil non-amended or amended with each material at 2% (w/w) were interacted with the fungicide at a concentration of 2 mg L⁻¹ for kinetics study and in the range 1–20 mg L⁻¹ for sorption isotherms. Kinetics results showed that metalaxyl-M onto the amendments and non-amended soil followed preferentially a pseudo-second-order model, thus indicating a chemisorption process. Sorption isotherm data of the product on BC and VC fitted well the Freundlich equation, whereas those on non-amended and amended soil followed preferentially a linear model. The KFads values were 995.2, 788.5, 55.2, 52.1, 6.4, 6.0, 3.4, 2.6 and 1.5 L kg⁻¹ for BC-G, BC-S, VC-M, VC-B, soil-BC-G, soil-BC-S, soil-VC-M, soil-VC-B and non-amended soil, respectively. Product desorption from each soil sample occurred to a lesser extent than sorption. Highly significant correlations (P < 0.005) were found between the values of sorption and desorption constants of all adsorbents and organic C content, thus confirming the prominent role of organic matter in the sorption process of metalaxyl-M.
... In organic soils Cu undergoes several adsorption processes in the organic fractions, such as particulate organic matter and humic acids, therefore acting as a reservoir increasing its availability for soil. In fact, the presence of copper at these elevated concentrations has been shown to produce considerable environmental effects (Fernandes et al. 2003;Calisi et al. 2009). ...
The paper reports the results of a laboratory test on the bioaccumulation and toxicological effects of sub-lethal soil concentration of copper, a widely used fungicide in organic farming, on DNA damage, a critical marker increasingly used in ecotoxicology in the earthworm Eisenia andrei. In the same experimental setting we evaluated gene expression of classical biomarker of stress induced by xenobiotic. [Heat Shock Protein 70 (HSP70) and Metallothionein (MET)], as well as genes coding for enzymes involved in detoxification of reactive oxygen species [Superoxide dismutase (SOD) and catalase (CAT)]. Additionally, expression of genes involved in the immune response were investigated: a Toll-like receptor (TLR), a receptor with cytolytic activity named Cytolytic Factor (CCF) and two antimicrobial peptides, fetidin (FET) and lysenin (LYS). Results showed significant time-dependent bioaccumulation of Cu and DNA damage at concentrations remarkably lower than those found in most agricultural soils worldwide. MET was increased as was FET and TLR. The present work gives new insights into the mechanisms of sub-lethal toxicity of copper as an environmental pollutant and in the identification of novel sub-lethal biomarkers of cellular response to the stressor such as immune response genes.
... These organic compounds are predominantly hydrophobic in nature. Hence, illite surfaces that are relatively more hydrophilic than non-swelling clays like kaolinite exhibit poor adsorption capacities for these pesticides, as low as 0.08 and 0.37 mg/g Dibenzothiophene sulfone [103] phenol [157] orthodiphenol [168] Humic Acid [170] Oil [155] Adsorption Capacity (mg/g) for linuron and atrazine respectively (Fig. 11) [83,168]. Charge density of clays may exert a significant impact on adsorption organic compounds. ...
... This could further inhibit adsorption on clay surface. In another instance, Illite-rich soils display reasonable uptake of metalaxyl fungicides at similar experimental settings [170]. However, a saline illite-rich soil (P10) obtained from marshes of southern Spain exhibited much higher adsorption affinity for metalaxyl in comparison. ...
Adsorption process has been widely used for treatment of wastewaters due to its simplicity and lower costs as compared to other traditional technologies. Among the alternative sorbent materials, the use of abundantly available clays for adsorption of organic pollutants has garnered increasing attention worldwide. Clays, in its natural and modified forms, have been extensively employed for the removal of organic contaminants from different wastewaters. The current review appraises the sorption performance of natural and modified clays for environmental remediation applications. The adsorption capacity of phenolic compounds, aromatic compounds, pesticides and herbicides, and other organic contaminants are comprehensively reviewed. The effect of the experimental conditions (pH, initial concentration (Co), surfactant loading, etc.) on the adsorption capacity is also appraised. Furthermore, the adsorption mechanisms, structures, and adsorptive characteristics of natural and modified clay sorbents are included. A statistical analysis of the adsorption isotherms reveals that Langmuir and Freundlich are the most examined models in fitting the experimental adsorption data. In addition, the adsorption kinetics is predominantly based on the pseudo-second-order model. The current review is an attempt to draw a prior knowledge about the technical viability of clay sorption process by assessing outcomes of the studies published between 2000 and 2018.
... The effects of pesticides have been widely investigated and several review articles have considered this type of contamination. Pesticides comprise a very wide group of substances with very different chemical structures that are targeted at different pest species and act very differently on soils (Fernandes et al., 2003;Arias et al., 2008;Gamble 2013). We therefore we did not consider them in this report. ...
Concern about environmental pollution has grown in the last few decades, amongst both specialists in the field and society at large. This concern is reflected in the numerous studies that have been published on this topic in recent years. Soil pollution has been somewhat neglected as a topic of study, relative to air and water pollution, which are considered harmful to human life. However, soil pollution is a particularly serious problem because of the impact on soil functioning and on the ecosystem as a whole. Although natural processes such as volcanic activity and weathering of the parent material contribute to soil pollution, anthropogenic activities represent the main cause of soil pollution. Apart from some accidental events, most pollution is generated by human activities such as industrial processes, transportation, construction, uncontrolled discharges, waste generation and agriculture. Agricultural land is particularly sensitive to pollution, partly because certain agricultural practices (soil preparation and tillage, soil fertilization, grazing, etc.) may affect basic soil properties, and partly because the soils usually display poor resilience. However, pollutants often reach already degraded agricultural soils and their impact will therefore be added to existing effects. The pollutants most frequently encountered in the agricultural sector include heavy metals, petroleum derived products, persistent organic pollutants, pesticides and fertilizers. Soil enzymes such as oxidoreductases and hydrolases have been widely used to investigate the impact of different pollutants on agricultural soils. However, the study findings are often inconclusive, because the impact of a given pollutant on the activity of different soil enzymes is influenced by various factors. In this report, we analyze the findings of different studies concerning pollution of agricultural soils.
... The effects of pesticides have been widely investigated and several review articles have considered this type of contamination. Pesticides comprise a very wide group of substances with very different chemical structures that are targeted at different pest species and act very differently on soils ( Fernandes et al., 2003;Arias et al., 2008;Gamble 2013). We therefore we did not consider them in this report. ...
Concern about environmental pollution has grown in the last few decades, amongst both specialists in the field and society at large. This concern is reflected in the numerous studies that have been published on this topic in recent years. Soil pollution has been somewhat neglected as a topic of study, relative to air and water pollution, which are considered harmful to human life. However, soil pollution is a particularly serious problem because of the impact on soil functioning and on the ecosystem as a whole. Although natural processes such as volcanic activity and weathering of the parent material contribute to soil pollution, anthropogenic activities represent the main cause of soil pollution. Apart from some accidental events, most pollution is generated by human activities such as industrial processes, transportation, construction, uncontrolled discharges, waste generation and agriculture. Agricultural land is particularly sensitive to pollution, partly because certain agricultural practices (soil preparation and tillage, soil fertilization, grazing, etc.) may affect basic soil properties, and partly because the soils usually display poor resilience. However, pollutants often reach already degraded agricultural soils and their impact will therefore be added to existing effects. The pollutants most frequently encountered in the agricultural sector include heavy metals, petroleum derived products, persistent organic pollutants, pesticides and fertilizers. Soil enzymes such as oxidoreductases and hydrolases have been widely used to investigate the impact of different pollutants on agricultural soils. However, the study findings are often inconclusive, because the impact of a given pollutant on the activity of different soil enzymes is influenced by various factors. In this report, we analyze the findings of different studies concerning pollution of agricultural soils.
... Metalaxyl has a water solubility of 8400 mg L À1 and a log P of 1.75 (Tomlin, 2006). It is highly polar and mobile in soils and besides organic matter, certain soil clay minerals may play an important role in its sorption (Bermúdez-Couso et al., 2011;Fernandes et al., 2003;Gondar et al., 2013;Sharma and Awasthi, 1997). The addition of organic amendments and modified clay minerals has been shown to enhance the retention of tebuconazole and/or metalaxyl in soils (Fenoll et al., 2011;Fernandes et al., 2006;Herrero-Hernández et al., 2011;Marín-Benito et al., 2012;Rodríguez-Cruz et al., 2007). ...
... The higher sorption of tebuconazole can be attributed to its greater hydrophobicity and affinity for soil organic matter ( Cadková et al., 2013) compared to metalaxyl. It is known that other factors, such as the amount and nature of mineral constituents, can dictate the sorption of metalaxyl in low organic carbon content soils (Bermúdez-Couso et al., 2011;Celis et al., 2013;Fernandes et al., 2003). In amended soil, sorption of tebuconazole and metalaxyl increased with the amount of clay and BC added, but the effect of adding clay was much more pronounced than that of adding BC. ...
Laboratory and field experiments were conducted to assess how the addition of oleate-modified hydrotalcite (clay) and biochar (BC) to an agricultural soil affected the sorption, leaching, persistence, and enantiomeric composition of soil residues of two chiral fungicides, tebuconazole and metalaxyl. Laboratory experiments showed that the sorption of both fungicides ranked as follows: unamended soil < BC-amended soil < clay-amended soil. The addition of clay at a rate of 1% increased metalaxyl soil sorption coefficient (Kd) from 0.34 to 3.14 L kg−1 and that of tebuconazole from 2.4 to 47.4 L kg−1. In our experimental set-up, field plots were either unamended or amended with clay (2 t ha−1) or BC (4 t ha−1), and subsequently treated with a mixture of tebuconazole and metalaxyl at 3 and 6 kg ha−1, respectively. The leaching, persistence, and enantiomer composition of fungicides residues were monitored by sampling at different soil depths (0–5, 5–10, 10–20 cm) for 98 days. No significant changes in the scarce mobility and long persistence of tebuconazole upon amending the soil with clay or BC were observed. In contrast, sorption to clay and BC particles reduced the leaching and degradation of metalaxyl and the clay increased its persistence in the topsoil compared to the unamended soil. The enantioselective analysis of tebuconazole and metalaxyl soil residues indicated that tebuconazole remained mostly racemic along the experiment, whereas for metalaxyl the concentration of S-enantiomer was greater than the concentration of R-enantiomer, more so at longer experimental times and deeper horizons. Nevertheless, for the top 0–5 cm soil layer metalaxyl remained more racemic in clay- and BC-amended soil than in unamended soil. Our results show that addition of amendments with high sorptive capacities can be beneficial in reducing leaching and degradation losses of chiral pesticide enantiomers from the topsoil, and that sorption by the amendments can influence the final enantiomeric composition of pesticide residues.
