Bioavailability of Lanthanides to Freshwater Organisms: Speciation, Accumulation and Toxicity
Abstract
The lanthanides consist of a group of fifteen homologous metals and together with scandium (Sc) and yttrium (Y) they are known as the rare earth elements (REE). Contrasting to what this name suggests they are not rare at all and lanthanides can be found in most soils and sediments in quantities comparable to those of Pb and Cd. However, their soluble concentrations are strongly limited by the low solubility products of lanthanides with carbonate and phosphate. The increasing industrial uses of lanthanides are accompanied by increasing emissions, which mainly end up in the aquatic environment. Therefore, it should be investigated if these emissions cause adverse effects on aquatic biota. This is the background of the research described here.
... Stauber and Binet, 2000;Lürling and Tolman, 2010;Bogers 1995c). Dissolved concentrations of La are mainly responsible for adverse effects (Weltje 2002). When EC50s are calculated from total concentrations, the toxicity is underestimated. ...
... e Effect concentration recalculated as mg lanthanum per liter, if necessary. f According to Weltje (2002) the applied medium reflects freshwater speciation conditions with an ionic strength between freshwater and seawater. g Estimated from graph. ...
... In contrast to the number of freshwater studies, very few tests were conducted with marine organisms and none were found for sediment or chronic studies. Weltje (2002) tested the sensitivity of the marine bacterium Aliivibrio fischeri (formerly: Vibrio fischeri) on lanthanum in a medium which reflects freshwater conditions (details in Table 5). Inhibition only occurred at high concentrations with an EC50 of 5.56 mg La L À 1 . ...
Rare earth elements (REE) used to be taken as tracers of geological origin for fluvial transport. Nowadays their increased applications in innovative environmental-friendly technology (e.g. in catalysts, superconductors, lasers, batteries) and medical applications (e.g. MRI contrast agent) lead to man-made, elevated levels in the environment. So far, no regulatory thresholds for REE concentrations and emissions to the environment have been set because information on risks from REE is scarce. However, evidence gathers that REE have to be acknowledged as new, emerging contaminants with manifold ways of entry into the environment, e.g. through waste water from hospitals or through industrial effluents. This paper reviews existing information on bioaccumulation and ecotoxicity of lanthanum in the aquatic environment. Lanthanum is of specific interest as one of the major lanthanides in industrial effluents. This review focuses on the freshwater and the marine environment, and tackles the water column and sediments. From these data, methods to derive quality criteria for sediment and water are discussed and preliminary suggestions are made.
... This behavior remains for LC 50 based on total nominal, total measured and calculated free ion concentrations ( Fig. 1b). Another experimental demonstration about lanthanide's ecotoxicity shows an increase in toxicity when increasing atomic numbers (Weltje, 2002;Weltje et al., 2004). In this study, phosphates were not present in the exposure medium and speciation calculation was taken into account to set the highest lanthanide concentration to avoid precipitation of lanthanide as carbonates and hydroxides. ...
... Stanley and Byrne (1990) found that gadolinium uptake by marine algae in carbonate-manipulated media was related to Gd 3+ but could not completely explain their observation based on Gd 3+ alone. Weltje (2002) concluded that effects of the free ion cannot be separated easily from those of its nitrate and carbonate complexes, and that total dissolved concentration may be used to express toxicity. However, we should note these conclusions derived from a study with a specific organism (V. ...
... Similar toxicity values were obtained when phosphates were present in exposure medium and endpoint was based on nominal concentration (Den Dooren de Jong, 1965;Tai et al., 2010). The data obtained by Weltje (2002), without presence of phosphate in the exposure medium and results based on measured concentration, show a strong increase in toxicity when increasing atomic number. It seems that, in the absence of ligands inducing Ln precipitation, ecotoxicity of lanthanide increases with an increasing atomic number. ...
... Also refers to US EPA 2012Lacour et al., 2005;Hutchison et al., 2004Monafo et al., 1976Pang et al., 2001). Unpolluted site vs polluted site Weltje et al., (2002) La, Ce, Eu Blue mussel Mytilus edulis Unpolluted site vs polluted site Riget et al., (1996) ...
... c BCF is calculated from total or nominal REE concentrations in the water and expressed in wet weight, except otherwise described. d BCF is dynamic i.e., accumulation not in equilibrium yet, is calculated as described inWeltje et al (2002) and expressed based on fresh weight of plant. e Values are calculated from dry weight of tissue. ...
This report by the Danish Centre for Environment and Energy (DCE) and Greenland
Institute of Natural Resources (GINR) aims to gather worldwide information on
excitotoxicity data on fluoride (F), rare earth elements (REEs), and naturally occurring
radionuclides (NORs) that can potentially be used in Greenland. The report is not
explicitly focused on Kvanefjeld and Tanbreeze mineral exploration projects in south
Greenland but on the mining and milling of minerals containing REEs, NORs, and F in
general in Greenland.
The report provides relevant information to be used as a basis for environmental
regulation and monitoring of mining projects and establish guidelines on
concentrations threshold values for the REEs, NORs, and F in water, soil, dust,
vegetation, berries, birds, and fish both in the mining area but also for the surrounding
environment. This report can also be used for teaching or as guide for the general
public, politicians, authorities, education, industry, and other Greenland stakeholders.
... Due to coexistence with other minerals, natural concentrations of lanthanides are similar to essential elements such as iodine, cobalt and selenium (Palasz and Czekaj 2000). Compared to the nonessential metals, concentrations of La, Ce and Nd tend to be higher than Pb and even concentrations of the less abundant REEs, (e.g., Tm and Lu), are typically higher than Cd in the earth crust (Weltje 2002). Cerium, at 60 mg kg -1 , is the most abundant lanthanide found in the Earth's crust, while the least plentiful are Tm and Lu (0.5 mg kg -1 ), which are still more abundant than gold (0.001 mg kg -1 ) (Kifle et al. 2013; Lewis and Jiménez-Villacorta 2013). ...
... REEs have low solubility and dissolved Ce and Lu (passing B0.45 lm filter) only ranged from 0.003 to 0.71 ng L -1 and 0.00004-0.007 ng L -1 , respectively, in pristine freshwater environments (Weltje 2002). Dissolved concentrations of other REEs are between these ranges. ...
... Due to coexistence with other minerals, natural concentrations of lanthanides are similar to essential elements such as iodine, cobalt and selenium (Palasz and Czekaj 2000). Compared to the nonessential metals, concentrations of La, Ce and Nd tend to be higher than Pb and even concentrations of the less abundant REEs, (e.g., Tm and Lu), are typically higher than Cd in the earth crust (Weltje 2002). Cerium, at 60 mg kg -1 , is the most abundant lanthanide found in the Earth's crust, while the least plentiful are Tm and Lu (0.5 mg kg -1 ), which are still more abundant than gold (0.001 mg kg -1 ) (Kifle et al. 2013; Lewis and Jiménez-Villacorta 2013). ...
... REEs have low solubility and dissolved Ce and Lu (passing B0.45 lm filter) only ranged from 0.003 to 0.71 ng L -1 and 0.00004-0.007 ng L -1 , respectively, in pristine freshwater environments (Weltje 2002). Dissolved concentrations of other REEs are between these ranges. ...
The distribution of 14 rare earth elements, Th and U was studied in streams of the study area at 21 sites. Aquatic mosses are known to accumulate even metabolically nonessential or toxic metals in concentrations much higher than their aqueous environment due to their unique morphology and physiology. Thus, the capacity of metal amplification in four aquatic mosses (Fontinalis squamosa, Brachythecium rivulare, Platyhypnidium riparioides and Thamnobryum alopecurum) was also evaluated as a potential bioindicator/biomonitoring tool. Thirteen REEs (0.001–2.81 μg L−1) and U were detected in the stream water. Mean content of lighter rare earth elements (LREEs) was higher than that of heavier rare earth elements (HREEs). Fourteen REEs and two actinides were detected in moss samples, including Yb and Th which were below detection level in water samples. LREE uptake (0.17–12.2 mg kg−1) was greater than HREE uptake (0.02–0.78 mg kg−1) in all mosses. Uptake of LREEs was observed in the order: B. rivulare >T. alopecurum >F. squamosa >P. riparioides and that of HREEs in the order: T. alopecurum >B. rivulare >F. squamosa >P. riparioides. Mean U content (0.68–1.62 mg kg−1) in the mosses was found in the order: B. rivulare >F. squamosa >T. alopecurum >P. riparioides. Th content ranged from 0.4 to 2.36 mg kg−1 in the order: B. rivulare >T. alopecurum >P. riparioides >F. squamosa. One-way ANOVA indicated a statistically significant difference (P ≤ 0.01) in mean concentrations of all elements (individually) in moss samples except for U. Highest bioconcentration factors of six REEs each were observed in B. rivulare (La, Ce, Sm, Eu, Tb and Dy) and T. alopecurum (Nd, Gd, Ho, Er, Tm and Lu). The highest BCFs for Pr and U were obtained in F. squamosa and P. riparioides, respectively. These species hold promise for biomonitoring studies in the future.
... Lanthanides are often used as analogs to actinides in biochemical and environmental studies, due the dangers inherent in working with radioactive materials [44]. Lanthanides are introduced into the waste cycle from medical waste associated with imaging technologies. ...
... Lanthanides are introduced into the waste cycle from medical waste associated with imaging technologies. They are relatively abundant in natural sources, as well, and in the earth's crust, concentrations of lanthanum (La), cesium (Ce) and neodymium (Nd), exceed those of lead, so these rare elements are often more prevalent than more common metals [44]. ...
The structural characteristics associated with the binding of beneficial metals (i.e. - Mg2+, Zn2+ and Ca2+) to natural proteins has typically received more attention than competitive binding by toxic metals (e.g. – Pb2+, Hg2+, Cd2+, La3+, etc.). In this thesis, a statistical analysis of Pb2+-binding in crystallized protein structures indicates that Pb2+ does not bind preferentially with nitrogen, as generally assumed, but binds predominantly with oxygen, and to a lesser degree, sulfur. A comparison of Ca2+ and Pb2+ indicates that Pb2+ binds with a wider range of coordination numbers, with less formal change, and with less defined structure than Ca2+. The Pb2+ ion also appears to displace Ca2+ with little conformational stress in calcium binding proteins (CaBP’s). Experimental data from the binding of metals with engineered fluorescent proteins indicate that both Pb2+ and Gd3+ will occupy grafted calcium-binding sites with greater affinity than Ca2+, and strong evidence is presented to support the hypothesis that Pb2+ and Gd3+ will bind non-specifically on the protein surface. These results suggest that toxicity is associated with two binding mechanisms: displacement of the metal cofactor which disrupts protein function, and non-specific binding which maintains higher solubility of the metal.
... Correlations of air pollution and medical statistics confirm the results of investigations39404142434445. Recently, in connection with the development of analytical methh ods, rare earth elements (lanthanides, Sc, Y), which were earlier beyond the reach of analytical techniques, have been extensively studied in environmental objects from the point of view of their toxicity [46, 47]. Production waste and discharge of factories, gasoo line and other fuel combustion products, household garbage in towns, fertilizers, pesticides, and many other things are sources of environmental pollution. ...
... On the other hand, being a living organism, it accumulates elements in particular amounts depending on their concentration in the nutritional medium where S. platensis cells grow. Recently, particular attention has been given to the study of the role played by trace elements in the human organism41424344454647. Trace elements are important for acid metabolism. ...
Development of methods for instrumental neutron activation analysis (INAA) and their applica�
tions in the life sciences are reviewed. Emphasis is placed on epithermal activation with reactor neutrons
(ENAA), and the advantages of this technique in analysis of environmental objects are shown. The results of
applied INAA studies in the field of the life sciences carried out at the world’s leading nuclear centers are
reported. Experience in employing a radioanalytical complex at the IBR�2 reactor (Frank Laboratory of
Neutron Physics, Joint Institute for Nuclear Research, Dubna) for such studies is summarized.
... One of the measures is bioaccumulation concentration factor (BCF), which includes different contaminants' level in the organisms with respect to the medium. BCF values are based on the ratio between plant concentrations against surface water, and it was observed that it's similar for most of the REEs throughout the year in all of the studied areas in Lemna minor, while BCF values of Potamogeton pectinatus were moreover similar for all REEs but differed between study areas, and for some other species, BCF varied in both spatial and temporal scales (Weltje 2003). A reduction in BCF with the atomic number was reported when the concentration ratio in the biota to pore water was measured. ...
Lanthanides (e.g. La, Gd, Nd, Ce) are being used increasingly due to their versatile applications in medical diagnosis, electronics, agriculture, industries, and research; hence, their global utility had been increased drastically in the last few decades. Lanthanide enrichment in agricultural fields due to repetitive use of fertilizer application and REE (rare-earth element)-based fertilizers leads to lanthanide-concentrated agricultural runoff to the water bodies consequently. Through biomagnification in the food chain, there is a risk of enrichment of these REEs in humans. Aquatic macrophytes are one of the important constituents of the food chain along with being a significant primary producer widely studied for metal accumulation and stress physiology. However, very limited knowledge on transfer processes, bioaccumulation, and distribution pattern of REEs is available. Chemical-assisted remediation and omics-guided phytoremediation using hyperaccumulator macrophytes are found to be the most popular methods, but macrophyte-based phytoremediation is preferable as it is eco-friendly and does not create any secondary pollutants. This chapter will cover the significant sources of REE contamination especially lanthanides, ecotoxicological effects on macrophytes, their stress physiology, and bioremediation strategies.
... The concomitant decrease of dissolved and increase of particulate REE in the test medium should be a consequence of REE precipitation as observed in numerous studies (Blinova et al., 2018;González et al., 2015;Romero-Freire et al., 2019). The difference between nominal and measured concentrations is probably related to REE precipitation but also to REE adsorption on glass walls (Crémazy et al., 2014;Weltje, 2002) despite the flask preconditioning (Lachaux et al., 2022a). These observations highlight the relevance to consider measured concentrations to characterize REE exposure and to avoid misinterpretation of observed biological effects (Lachaux et al., 2022b). ...
... Hence, environmental emissions of REE need to be monitored. This demands development of adequate monitoring approaches , selection of biomonitors and adequate analytic techniques [14]. Instrumental neutron activation analysis (INAA) is a powerful tool giving an opportunity to determine the contents of a number of chemical elements in a small single sample. ...
Experiments in physics, Astro-particle physics and cosmology that require careful shielding against cosmic rays include dark matter searches, studies of radioactive decays, and neutrino detection experiments. The need for such shielding has motivated the construction of laboratory caverns in mines and adjacent to tunnels under mountains. There are currently about a dozen such laboratories, in existence or under construction, all in the Northern Hemisphere. A motivation has been made for the establishment of a Southern Hemisphere facility. In this paper a feasibility study of measurements of radon in air (using electret ion chambers and alpha spectroscopy), background gamma ray measurements (inside/outside) the tunnel using scintillator (inorganic) detectors, cosmic ray measurements using organic scintillators and radiometric analyses of representative rock samples for the establishment of such a facility in the South Africa is presented.
... Hence, environmental emissions of REE need to be monitored. This demands development of adequate monitoring approaches , selection of biomonitors and adequate analytic techniques [14]. Instrumental neutron activation analysis (INAA) is a powerful tool giving an opportunity to determine the contents of a number of chemical elements in a small single sample. ...
The contents of 23 trace elements (Sc, V, Cr, Mn, Fe, Co, Zn, As, Se, Br, Rb, Sr, Mo, Ag, Sb, I, Ba, La, Ce,
Sm, Eu, Hf, Ta) were quantitatively determined in soft tissues and shells of mass non-indigenous
bivalve mussels—farmed Pacific oysters (Crassostrea gigas) and farmed and wild invasive Mediterranean
mussels (Mytilus galloprovincialis) at the Atlantic coast of South Africa. The study revealed
that the contents of the majority of elements in the soft tissues of both species were higher
than those in the shells. The tissues of wild invasive Mediterranean mussels contain higher levels
of a range of trace elements comparing to farmed mussels. The tissues of Pacific oysters contain
much higher levels of almost all elements studied compared to the tissues of Mediterranean mussels.
Higher content of zinc in the mussels and oysters from Saldanha Bay may evidence anthropogenic
pollution of the bay’s ecosystem by this metal, which necessitates continued monitoring of
levels of potentially toxic metals. Both alien species, and especially Pacific oysters, may serve as
reliable biomonitors for trace elements in marine ecosystems. Both species are rich in essential
elements and provide nutritionally-valuable seafoods.
... In the aquatic and soil environments, REEs can be found especially in the polluted regions [18] [19], possibly affecting the biota within [20] [21]. REEs are emitted to both aerial and aquatic environments from semiconductor industries mostly in East Asian countries [22] and hospitals in developed countries (REEs used for medical imaging) [23], respectively. ...
Paramecium bursaria is an unicellular organism that lives widely in fresh water environments such as rivers and ponds. Recent studies have suggested that in vivo cellular robotics using the cells of P. bursaria as micro-machines controllable under electrical and optical stimuli, has a variety of engineering applications such as transport of micro-sized particles in the capillary systems. The present study aimed to test if the swimming cells of P. bursaria, implementable in capillaries or on chips, are applicable for detection of metal ions. For model assays, rare earth elements (REEs) were chosen as target chemicals. In P. bursaria, LC50 values for REE ions ranged between 2.0 and 62.7 µM. Among them, Sc was shown to be most toxic. In addition to the lethal impacts of REE ions, most of REE ions at sub-lethal concentrations at around 10 - 30 µM, showed inhibitory action against the motility of the cells during the electrically forced motility known as galvanotaxisis. In conclusion, in the non-lethal ranges of REE concentration, swimming cells of P. bursaria report the presence of REE ions, by lowering the motility.
Der Artikel enthält folgende Kapitel: EinleitungUmwelt-, Bioanalytik, chemische Kriterien von Stoffresorption und -transport sowie Methodik der vergleichenden Datenauswertung“Auswahlregeln” für essenzielle ElementeFazit und DanksagungGlossarLiteratur
There is no direct relationship between essentiality patterns of chemical elements and analytical data for biological materials:
while any organism selects some (dozens of) chemical elements for running its biochemical functions, several of these may
be present, both required and tolerable at very low concentration levels only (V, Se) though essential whereas there are substantial
amounts of non-essential metal ions in the same organism (Al, Rb, Sr, Ti, etc.). There are also differences with respect to
biochemical effects. In additions, elements do interact during uptake: regardless whether an element is essential by itself,
it may influence the uptake of another – regardless whether essential or non-essential – one, e.g. by competing for the same
carriers. There also are changes of effects (Fig. 1.2) which can be detected by changes of plant growth rates.
By the Biological System of Elements, originally (Markert 1996) an array of chemical elements was denoted describing their
distribution in green plants and abundance correlation among plant species, irrespective of biochemical “roles” (e.g., essentiality
as a component of enzymes) and functions. Later on, the present author went to give a causal account which draws on different
physicochemical features and necessities of biochemistry – including effects of elements other than C, N, S, O, H and P –
and extending the scope of interest to other living beings and their interactions in ecosystems, that is, to stoichiometric
ecology.
Zusammenfassung Derzeit bestehen nur wenige etablierte organismische Testverfahren zur Erfassung von reproduktionstoxischen Effekten, die
eine Exposition gegenüber Gesamtsedimenten berücksichtigen. Ein hierfür gut geeigneter Testorganismus ist die parthenogenetische
ZwergdeckeischneckePotamopyrgus antipodarum. Sie gehört zu den ovoviviparen (lebendgebärenden) Prosobranchiern und lebt in den obersten Schichten von Süß- und Brackwassersedimenten.
Als empfindlicher Parameter zur Indikation reproduktionstoxisch wirkender Sedimentkomponenten erwies sich die Anzahl der (neugebildeten)
Embryonen im Brutraum — dieser Endpunkt vermag zudem auf eventuell vorhandene östrogene Wirkstoffe im Sediment hinzuweisen.
Mit Hilfe dieses 28 Tage umfassenden Biotests wurden in Laboruntersuchungen die Wirkungen verschiedener Umweltchemikalien,
wie z.B. Triphenylzinn und Bisphenol A, aufP. antipodarum in umweltrelevanten Konzentrationsreihen getestet. Darüber hinaus wurde die Eignung des Biotests für die Ermittlung und Untersuchung
der Wirkung komplexer Kontaminanten anhand von verschiedenen realen Flussedimenten unterschiedlichen Belastungsgrades — aus
Neiße und Oder — erprobt.
The lanthanide elements, Th and U were measured in soils and agricultural crops collected in an area polluted by emissions
from a phosphate fertilizer plant. Concentrations of the above elements in the soil and crop samples were determined by instrumental
neutron activation analysis (INAA). Selected crop samples were also analyzed using radiochemical neutron activation analysis
(RNAA) based on alkaline-oxidative fusion of the irradiated samples followed by precipitation of REE oxalates. Elevated levels
of lanthanides, Th and U were found in some samples, especially in wheat chaff and parsley.
The effects of two suspected endocrine-disrupting chemicals, the xeno-androgens triphenyltin (TPT) and tributyltin (TBT), were investigated in a new whole-sediment biotest with the freshwater mudsnail Potamopyrgus antipodarum (Gastropoda, Prosobranchia). Artificial sediments were spiked with seven concentrations, ranging from 10 to 500 microg nominal TPT-Sn/kg dry weight and TBT-Sn/kg dry weight, respectively. We analyzed the responses of the test species after two, four, and eight weeks exposure. For both compounds, P. antipodarum exhibited a sharp decline in the number of embryos sheltered in its brood pouch in a time- and concentration-dependent manner in comparison to the control sediment. The number of new, still unshelled embryos turned out to be the most sensitive parameter. The lowest-observed-effect concentration (LOEC) was equivalent to the lowest administered concentration (10 microg/kg of each test compound) for most parameters and thus no no-observed-effect concentration (NOEC) could be established. The calculation of effect concentrations (EC10) resulted in even lower values for both substances (EC10 after eight weeks for unshelled embryos: 0.03 microg TPT-Sn/kg, EC10 after four weeks for unshelled embryos: 0.98 microg TBT-Sn/kg). Our results indicate that P. antipodarum is highly sensitive to both endocrine disruptors TPT and TBT at environmentally relevant concentrations.
Metal ions interact with biological materials and their decomposition products by ligation (coordination complex-formation with certain moieties containing O, N, S, etc.). The extent of this interaction depends on the identities of both ligand and metal ion and can be described by some equation derived from perturbation theory. Uptake of metal ions - including highly toxic ones - from soils is controlled by a competition between root exudate components and soil organic matter (SOM) for the ions. SOM consists of a variety of potential ligands which evolve during humification towards more efficient binding (retention) of metals such as Cu, Ni, Cr but also of toxicants like U, Cd. The actual way of interaction can be inferred from stoichiometry of the involved compounds and the C/N ratio in the soil, providing predictions as to which metals will be most efficiently shuttled into green plants or fungi, respectively. The latter, selective process is crucial for closing nutrient cycles and sensitively depends on C/N ratio and the extent of "forcing" by onfalling leaf or needle litter. Therefore, analytical data on the soil can be used to predict possible risks of exposition to toxic metals also for human consumption of plant parts.
Industrial emissions of lanthanides to aquatic ecosystems increase, but knowledge of the environmental fate of these metals is limited. Here we focus attention upon the distribution of lanthanides in freshwater ecosystems, describing lanthanide partitioning between sediment, water and biota. Since lanthanides are often used as oxidation-state analogues for actinides, their distribution can reflect long-term behaviour of the radioactive transuranics. Concentrations of all 14 naturally occurring lanthanides were measured by ICP-MS in Sago pondweed (Potamogeton pectinatus), common duckweed (Lemna minor), seven different mollusc species (tissue and shell), two sediment fractions (< 2 mm and < 63 microm), surface water and sediment pore water from five locations in The Netherlands. In all samples, the typical 'saw-tooth' lanthanide pattern was observed, which implies that lanthanides are transported as a coherent group through aquatic ecosystems. Typical deviations from this pattern were found for Ce and Eu and could be explained by their redox chemistry. The variation in concentrations in abiotic fractions was limited, i.e. within one order of magnitude. However, variations of up to three orders of magnitude were observed in biotic samples, suggesting different affinities among organisms for lanthanides as a group, with significant differences only among molluscs and pondweed samples in relation to sampling location. For P. pectinatus it was shown that pore water was the most important lanthanide source, and for snails, food (plants) seems to be the dominant lanthanide source. Lanthanides were not equally distributed between mollusc shell and tissue and the ratio of lanthanide concentrations in shell and tissue were dependent on the sampling location. Shells contained much lower concentrations and were relatively enriched in Eu, and to a lesser extent in Ce. Bioconcentration factors for lanthanides in plants and snails relative to surface water were typically between 10000 and 100000 l x kg(-1) dry matter, while sediment-water partition coefficients were between 100000 and 3000000 l x kg(-1) dry matter. There was a low extent of biomagnification in the plant-to-snail system, with a maximum biomagnification factor of 5.5. Many distribution coefficients displayed a slight decrease with atomic number. This can be attributed to the general increase in ligand stability constants with atomic number, keeping the heavier lanthanides preferentially in solution.
Lanthanide emissions to the environment increase as a result of the growing industrial applications of these elements. However, robust data to evaluate the environmental fate of lanthanides are scarce. This article describes the accumulation and elimination of lanthanum (La) by common duckweed (Lemna minor L.). Speciation modeling was performed to assure that solubility products were not exceeded. It also showed that La was predominantly associated with ethylenediaminetetraacetic acid (EDTA). Lanthanum concentrations in plants and medium and the amounts sorbed to glass vessels were quantified by using the radioisotope 140La. The amount of La adsorbed on the glass reached values of 25% of the total La present. A model was formulated to describe La uptake in exponentially growing duckweed in the presence of an adsorptive surface. Growth-induced dilution appeared more efficient in lowering plant La concentrations than actual elimination. An elimination study revealed two compartments, of which the smallest eliminated 50 times faster than the bigger compartment, which eliminated mainly by growth dilution. The average bioconcentration factor was 2,000 L/kg fresh weight and 30,000 L/kg dry weight, comparable with those of other higher plants. At the applied concentration of 10 nM, no effects were observed on duckweed growth. However, the high bioconcentration factor warrants monitoring of lanthanide emissions.
Filtration of a solution may lower metal concentrations through adsorption of metal species to the filter. Processes such as filter-sterilizing nutrient solution and filtration of field water are sensitive to these sorption artifacts, yet basic data on the affinity of different filters for metals are lacking. This article describes the adsorption of five metals to eight types of 0.2-microm membrane filters used for sterilizing a plant (Lemna minor L.) culture medium. Filters of cellulose acetate, cellulose nitrate, mixed cellulose ester, nylon, polyamide, polycarbonate, polyester, and polyvinylidene fluoride were tested for their affinity toward mono- (K), di-(Mn, Cu, Zn), and trivalent (lanthanum [La]) metals. Metal concentrations were quantified using radioisotopes and speciation was calculated. Results showed that metals had the lowest affinity for polycarbonate and nylon filters and the highest affinity for cellulose- and polyester-type filters. Furthermore, it was shown that the metal load on cellulose filters correlated best with free ion concentrations (indicating electrostatic attraction), while loads on other filters correlated better with total metal concentrations. Filtering a 5-ml solution of pH 5 did not affect its metal concentrations, ranging from 10 nM (La) to 49 microM (K). To minimize filtration artifacts, we propose using polycarbonate or nylon filters, especially when dealing with low volumes of high pH and low metal species concentrations.
Toxicity studies with lanthanides and Vibrio fischeri -importance of the free ion and QSAR development
- L Weltje
- J J M De Goeij
Weltje, L., de Goeij, J. J. M.: Toxicity studies with lanthanides
and Vibrio fischeri -importance of the free ion and QSAR
development. In: Abstracts of the 13 th Annual Meeting of
SETAC-Europe. Hamburg, Germany, 2003, p. 107.