Toxicity Of Cu Research Articles

Removal of low levels of Cu from ongoing sources in the presence of other elements – Implications for remediated contaminated sediments

Mesocosms were used to investigate the effects of Cu influx, alone and in the presence of other elements, on sediments remediated by active caps, passive caps, and in situ treatment. Competitive interactions between Cu and other elements were investigated because contaminants often co-occur. Elements in surface water remained at significantly lower concentrations in mesocosms with apatite and mixed amendment caps than in mesocosms with passive sand caps or uncapped sediment. Element concentrations in Lumbriculus variegatus were significantly higher in untreated sediment than in active caps and significantly related to element concentrations in sediment measured by DGT probes. The cumulative toxicity of Cu mixed with other elements was greater than the toxicity of Cu alone in treatments without active caps, but the ability of active caps to control Cu was not affected by the presence of other elements. Active caps can protect remediated sediments by reducing bioavailable elements in ongoing contamination.

Kinetics simulation of Cu and Cd removal and the microbial community adaptation in a periphytic biofilm reactor

Periphytic biofilm reactor (PBfR) shows great potential in pollutants removal. However, few studies were focused on mathematical model of pollutants removal in PBfR. A three-step PBfR was designed and a new model was developed to simulate the kinetics of Cu and Cd removal from simulated wastewater. The results show that the PBfR could remove 99.0% Cu and 99.7% Cd from liquid wastewater. The experiment data could be well fitted with a high correlation coefficients both for Cu and Cd. The microbial community in the PBfR could be self-adjusted to tolerate the toxicities of Cu and Cd, resulting in sustainable and high decontamination efficiencies. The eukaryote in the PBfR played a vital role in Cu and Cd removal. The prokaryote showed negative effect on Cu and Cd removal, though it had more diversity than eukaryote. This study provides a new approach for Cu and Cd removal and their kinetics simulation in photoautotrophic bioreactor.

Copper toxicity in Bristol Bay headwaters: Part 1-Acute mortality and ambient water quality criteria in low-hardness water.

The world-class Alaskan Bristol Bay salmon fishery and vast deposits of copper (Cu) and other metals in the watershed warrant further investigation into the potential toxicity of Cu to salmonids under the low water-hardness conditions that occur in the watershed. Therefore we investigated the acute toxicity of Cu to rainbow trout (Oncorhynchus mykiss) and fathead minnows (Pimephales promelas) in low-hardness water (∼ 30 mg/L as CaCO3 ) formulated in the laboratory and collected from the Bristol Bay watershed. The median lethal concentration (LC50) for rainbow trout exposed to Cu in low-hardness laboratory water was 16 μg Cu/L (95% confidence intervals [CIs]: 12, 21; dissolved Cu, filtered to 0.45 μm). The LC50 values for fathead minnows exposed to Cu in low-hardness laboratory water or site water were 29 and 79 μg Cu/L (95% CIs: 23, 35 and 58, 125; dissolved Cu), respectively. The biotic ligand model (BLM) LC50 estimates for these bioassays were 1.3 to 2.3 times higher than the actual LC50 values. We also calculated and analyzed acute Cu water quality criteria, also known as criterion maximum concentration (CMC), using hardness-based methods and the BLM for water samples collected throughout the Bristol Bay watershed in 2007. Biotic ligand model CMCs ranged from 0.05 to 17.5 μg Cu/L and hardness-based CMCs ranged from 2.3 to 6.1 μg Cu/L for the 65 samples analyzed. Our results show the need for site-specific research and subsequent water quality guidelines in low-hardness aquatic habitats. Environ Toxicol Chem 2019;38:190-197. © 2018 SETAC.

Oxidative damage induced by copper in testis of the red swamp crayfish Procambarus clarkii and its underlying mechanisms

Copper (Cu) is one of the most widespread environmental pollutants and is known to exert multiple toxic effects including reproductive toxicity. In this study, we investigated the toxic effect of Cu on reproduction of the red swamp crayfish (Procambarus clarkii), an economic crustacean species, by exposing adult male crayfish to 0.03 and 3.00 mg/L Cu2+ for 7 days. The results showed that Cu2+ exposure induced oxidative stress accompanied by elevated reactive oxygen species (ROS) and malondialdehyde (MDA) levels in testes, and resulted in decreased sperm quality and abnormal testicular structures with apoptotic germ cells and vacuolisation in Sertoli cells. To reveal the molecular mechanism of Cu2+-induced oxidative damage in crayfish testes, we sequenced, assembled and annotated the transcriptome for crayfish testes, using the Illumina sequencing approach. After the 3.00 mg/L Cu2+ treatment, 6745 genes with differentially expressed profile were identified, of which many genes were involved in cellular response to ROS based on Gene Ontology enrichment analysis. Further, KEGG analysis demonstrated that genes with up-regulated expression levels significantly enriched in mitochondria oxidative phosphorylation pathway, suggesting disturbed mitochondrial electron transport chain was probably a main source of Cu2+-induced ROS production in testes. This study represented the first use of transcriptome to investigate the toxic effect of Cu2+ on male crayfish reproduction, and the pathways identified underlying Cu2+ toxicity at molecular level provide a novel insight into the reproductive toxicity of Cu in crustaceans.

Synthesis, DNA binding and cancer cell toxicity of Cu(II)-complexes of a tricationic nitro-porphyrin or analogous porphyrins with pendant Schiff bases derived from reduction of the nitro group

Three Cu-complexes, one is containing 5-(4-Nitrophenyl)-10,15,20-tris (4-N-methylpyridinium) porphyrin ligand (labeled as CuP-1) and the others with meso-10,15,20-tris (4-N-methylpyridinium)-5-(4′-X-schiff base) porphyrin ligands (X referred to salicylaldehyde (CuP-2), o-Vanillin (CuP-3) respectively) have been successfully synthesized and well characterized. Various spectroscopic approaches indicate that three Cu-complexes could effectively bind with CT-DNA through intercalation mode, especially CuP-1, which has better binding affinity than its analogs. Moreover, the antiproliferative activity of the delegate complex CuP-1 have been studied by MTT assay, and CuP-1 exhibits gratifying cytotoxicity towards TCA8113 (tongue squanmous carcinoma) cell lines.

Nitration of amyloid-β peptide (1–42) as a protective mechanism for the amyloid-β peptide (1–42) against copper ion toxicity

It is known that copper ion (Cu(II)) binds to amyloid-β peptide (Aβ), induces Aβ oligomer formation and ultimately exacerbates Aβ-aggregation neurotoxicity in Alzheimer's disease (AD). It becomes interesting to know that how this chemical modification of Aβ would affect interaction of Aβ and Cu(II) and their roles in the development of AD. In this work, we investigated the interaction of Aβ1–42 nitration with the toxic Cu(II). It showed that Cu(II)induced Aβ1–42 nitration in the presence of nitrite and hydrogen peroxide. Circular dichroism studies also revealed significant conformational change of Aβ1–42 and Tyr10 nitrated amyloid-β peptide(1–42) (Aβ1–42NT) when interacting with Cu(II). Even though nitration did not alter the binding of Aβ1–42 to Cu(II) or the peroxidative activity of Aβ1–42-Cu(II) complex, nitration ameliorated the aggregation and neurotoxicity of Aβ1–42 induced by Cu(II), which was also further confirmed by the cell study. Given our previous findings that Aβ nitration dramatically inhibited its aggregation and thus reduced its toxicity, we speculated that nitration of Aβ1–42 altered its intermolecular interaction, which protected itself against the toxicity of Cu(II). Based on this hypothesis, we propose that nitration of Aβ1–42 may be an important protective mechanism for normal function of Aβ1–42 and deserves more attention in AD drug development.

The Chronic Effects of Copper and Cadmium on Life History Traits Across Cladocera Species: A Meta-analysis

The effect of sublethal concentrations of heavy metals on cladoceran growth and reproduction is a cornerstone of modern ecotoxicology. However, the literature contains assays across numerous concentrations, on numerous species and genotypes, and conditions are far from consistent. We undertook a systematic review of the sublethal effects of copper and cadmium concentrations on Cladocera spp. life history (reproduction, maturation age, and somatic growth rate). Using meta-analysis, we tested the hypothesis that the effects of increasing Cu and Cd concentrations on traits may vary by species. We also evaluated where possible whether the effect of metal concentrations on traits vary by water hardness, exposure duration, or whether the metals were delivered in aqueous solution or via food. We surveyed > 200 papers, resulting in a set of 32 experimental studies representing 446 trials where the results were presented compared with Daphnia magna—the most commonly assayed species. We found qualitatively similar effects of Cu and Cd on life history traits that included reduction in reproduction and somatic growth rate and delay of maturation. Cladocera species showed marked variations in their susceptibility to metals, and D. magna was found to be the least sensitive species to sublethal changes in reproduction. The effects were largely consistent for aqueous vs. dietary food. Water hardness, where data were available, had no detectable effect. Available data indicate that exposure duration had no effect on the toxicity of Cu but did for D. magna reproductive response to Cd. Our study highlights the importance of including species identity when considering toxicological testing and regulation development.

Alteration of bioaccumulation mechanisms of Cu by microalgae in the presence of natural fulvic acids

The impact of natural fulvic acids (FAs) on the toxicity and bioaccumulation of Cu by Chlorella pyrenoidosa was studied. FAs extracted from Taihu Lake were separated into three fractions using dialysis bags: F1 (<500 Da), F2 (500–1000 Da) and F3 (>1000 Da). The results showed that the F3 fraction with a larger molecular weight contained less acidic groups and unsaturated aliphatic structures than F1 and F2, and it showed stronger alleviation of the toxicity of Cu to algae. In the presence of F1∼F3, the bioaccumulation curve of Cu in algae intersected with the straight line in the binary system of Cu-algae at approximately 5.3 × 10−3－6.0 × 10−3 mM of Cu equilibrium concentration, showing an inhibition of bioaccumulation of Cu in lower concentrations but an enhancement in higher Cu concentrations. The ratio of {Cu}ads/{Cu}int was used to clarify the transformation mechanism on adsorption; the transition interval occurred at a ratio of 3.5–4.4. This ratio indicated a shift from a mechanism of slow trending to equilibrium to a mechanism with rapid increase, which may be due to the bridging action of Cu to form a ternary complex of FA-Cu-algae and the occurrence of multilayer adsorption. The promotion order of F1> F3> F2 was consistent with percentages of the carboxyl group in total acidic functional groups in the FAs. This research is helpful for improving the accuracy of present models for the prediction of heavy metal risks in aqueous environments.

The prediction of combined toxicity of Cu–Ni for barley using an extended concentration addition model

Environment pollution often occurs as an obvious combined effect involving two (or more) elements, and this effect changes with the concentrations of the different elements. The effects on barley root elongation were studied in hydroponic systems to investigate the toxicity of Cu–Ni combined at low doses and at a fixed concentration ratio. For low doses of Cu–Ni, the addition of Ni (<0.5 μM) to Cu significantly decreased Cu toxicity for barley, but the addition of Cu (<0.25 μM) had no significant effect on Ni toxicity. At a fixed concentration ratio, according to the single effective concentration (EC) (barley root elongation inhibitory concentration) values of Cu and Ni, five sets of Cu–Ni fixed ratios were used: ECn(Cu)+ECm(Ni) (n + m = 100) (ECn and ECm indicate toxicity unit value for n% and m% inhibition of barley root length, respectively). The calculated toxicity unit value for 50% inhibition of root length ranged from 0.44 to 0.98 (i.e., <1), indicating a synergistic effect. To consider the interactions between the metal ions, the extended concentration addition model (e-CA) was established by integrating the Cu–Ni interaction into the concentration addition model (CA), and the data of two groups (the low doses of Cu–Ni and at a fixed concentration ratio) were respectively fitted. The e-CA accurately predicted the root length of barley under the Cu–Ni combined action. The correlation coefficient (r) and the root-mean-square error (RMSE) between predicted and observed values were 0.97 and 6.6 (low-dose group) and 0.96 and 8.12 (fixed-ratio group), respectively, and e-CA significantly improved the prediction accuracy compared to the traditional CA model without consideration of the Cu–Ni competition (r = 0.89, RMSE = 14.16). The results provided a theoretical basis for evaluation and remediation of soil contaminated with heavy metal composites.

The insects as an assessment tool of ecotoxicology associated with metal toxic plants

In this article, the assessment of lethal effects of Copper (Cu) on Luffa acutangula and Spinacia oleracea plants investigated in relation to the presence of insect species Oxycarenus hyalinipennis. The analysis of Cu-treated plants displays the information of rapid growth of Oxycarenus hyalinipennis species in triplicate. However, results showed that the impact of metal toxicity appeared as the reduced growth rate of plants, and dense growth of the insect species Oxycarenus halinipennis followed by the chewing/degradation of the toxic plant. The insect's inductees into polluted plants were justified by morphological and primary molecular level using plant stress hypothesis through analysis of the primary chemistry of leaves and roots. That includes various sugar contents which substantiated that these compounds act as the best feeding stimulant from oviposition to adult stage of the insects and accountable for the enactment of insects in the toxic plants. The relationship of these insects to the toxic plants linked with the higher contents of glucose, carbohydrates, and cellulose. The higher carbohydrate and cellulose content in both plants species under Cu accumulation exhibited more signs of insect mutilation over control plants and the lack of chemical resistances allowed the adult insects to spread, survive, reproduce and live long. The presence of insects developed relationships that assimilate all developmental, biological, and the interactive toxicity of Cu in both plant species which indicate the risk associated with these plants.

Biochemical Effects of the Toxic Interaction of Copper, Lead and Cadmium on Clarias gariepinus.

Background.The presence of heavy metals in the aquatic environment is a concern because of potential toxicity and threats to plant and animal life.Objective.The present study evaluated the joint action toxicity and biochemical effects of sublethal concentrations of copper (Cu), lead (Pb) and cadmium (Cd) against Clarias gariepinus over a period of 28 days.Methods.We procured fingerlings (weight: 5–8 g; length: 4.5–6.0 cm) and juveniles (weight: 20–25 g; length: 14.5–17.5 cm) from a commercial fish farm in Bariga, Lagos state, Nigeria. Test toxicants were selected from the analyzed heavy metals in the field based on their deviation from World Health Organization, Federal Environmental Protection Agency and United States Environmental Protection Agency standards. Fish were randomly loaded into a 4-L glass aquaria for the bioassay per toxicant concentration of two replicates and untreated control (dechlorinated tap water).Results.The derived 96 hour lethal concentration 50 (LC50) value of Cu (2.11 mg/L) was the most toxic followed by Cd (24.18 mg/L) and Pb (34.48 mg/L), which was the least toxic of the singly tested pollutants. The analysis of dose-response data of the joint action toxicity of Cu and Cd, and Cu and Pb determined 96 hour LC50 values of 1.804 mg/L and 2.15 mg/L, respectively. The interactions between the mixture of Cu:Cd conformed with the model of synergism (synergistic ratio (SR)>1 and relative toxic units (RTU)>1), while the interaction between Cu:Pb was found to be antagonistic (SR<1), with an SR value of 0.98. The biochemical effects study revealed that malondialdehyde (MDA) levels decreased significantly (P<0.05) in the exposed fish, reduced glutathione was not significant at (P<0.05), and levels of superoxide dismutase (SOD), catalase, glucose and cholesterol were significantly different (P<0.05).Discussion.The observed increased in the glutathione level in the Cu:Cd mixture and a corresponding decrease in MDA concentration in the liver of test animals revealed the ability of fish to overcome the effects of lipid peroxidation in this group because the Cu ion is displaced by Cd, and the fish were able to catalyze the breakdown of hydrogen peroxide via the Fenton reaction.Conclusions.Further studies on the joint action toxicity of heavy metals are needed in order to further determine their concentration in the local environment.Ethics Approval.Study protocols were approved by the Health Research Ethics Committee of the University of Lagos.

The activities of microbial communities in Huixian Wetland sediments under the interactive toxicity of Cu(II) and pentachloronitrobenzene

The unbonded Cu(II) and pentachloronitrobenzene (PCNB) in the sediment of Huixian Wetland were determined. Their toxic effects on the microbial communities in the sediment were explored by treating the sediment with Cu(II) (CuSO4·5H2O) and PCNB individually or jointly. The Complexation/Transformation ratios of these two toxicants resulted from the microbial communities were also investigated. Tow groups of sediments were classified according to the content of Cu(II) and PCNB in it, namely, higher level of Cu(II) and PCNB detectable for the first one (G1), which was collected from the lakes located at lower reaches of the water flow in the wetland, the other one with low level of Cu(II) and PCNB undetectable (G2), which was collected from the sites of upper flow of water, the foremost outlet of the subterranean streams flowed in to the wetland. The Cu(II) and PCNB content in the wetland sediments were as high as 185.63±16.2μg·g−1 and 0.17±0.07μg·g−1for the G1, but for the G2, 17.4±1.2μg·g−1 and undetectable, respectively. The 40h IC50 values for the microbial communities of Cu(II) and PCNB, as treated with Cu(II) and PCNB individually, were 3572μg·g−1 and 8μg·g−1 for the G1, 3053μg·g−1 and 4.5μg·g−1 for the G2, respectively. These values, when the microbial communities were treated with Cu(II) and PCNB simultaneously, increased to 7520μg·g−1 and 10.1μg·g−1 for the G1 and for the G2 3196μg·g−1 and 8.1μg·g−1, respectively. The 40h additivity indexes (AI) for the interactive toxicity of Cu(II) and PCNB on the microbial communities in the sediment of G1 and G2 were −0.26 and −1.82, respectively. These results indicated that the microbial communities in Huixian Wetland that previously exposed to higher level of Cu(II) and PCNB had a higher tolerance to the corresponding toxicants, and the interactive toxicity of Cu(II) and PCNB was antagonistic under the testing conditions. Furthermore, the microbial communities in the sediment of G1 generally showed higher Cu(II) and PCNB Complexation/Transformation ratios against its counterpart in the G2, no matter Cu(II) and PCNB stressed separately or together. Moreover, the correlations of added doses of pollutants and microbial communities activities in the sediment were discussed. The conclusion were that microbial communities in the sediment of Huixian Wetland had a higher tolerance against Cu(II) but lower against PCNB, and the contents of the later in this sediment might have approached to the dose which the microbial communities could be furthest tolerable.

Validation of a biotic ligand model on site-specific copper toxicity to Daphnia magna in the Yeongsan River, Korea

The objective of this study was to determine whether the water effect ratio (WER) or biotic ligand model (BLM) could be applied to efficiently develop water quality criteria (WQC) in Korea. Samples were collected from 12 specific sites along the Yeongsan River (YSR), Korea, including two sewage treatment plants and one estuary lake. A copper toxicity test using Daphnia magna was performed to determine the WER and to compare to the BLM prediction. The results of the WER from YSR samples also indicated significantly different copper toxicities in all sites. The model-based predictions showed that effluent and estuary waters had significantly different properties in regard to their ability to be used to investigate water characteristics and copper toxicity. It was supposed that the slight water characteristics changes, such as pH, DOC, hardness, conductivity, among others, influence copper toxicity, and these variable effects on copper toxicity interacted with the water composition. The 38% prediction was outside of the validation range by a factor of two in all sites, showing a poor predictive ability, especially in STPs and streams adjacent to the estuary, while the measured toxicity was more stable. The samples that ranged from pH 7.3–7.7 generated stable predictions, while other samples, including those with lower and the higher pH values, led to more unstable predictions. The results also showed that the toxicity of Cu in sample waters to D. magna was closely proportional to the amounts of acidity, including the carboxylic and phenolic groups, as well as the DOC concentrations. Consequently, the acceptable prediction of metal toxicity in various water samples needs the site-specific results considering the water characteristics such as pH and DOC properties particularly in STPs and estuary regions.

Evaluation of the effect of test medium on total Cu body burden of nano CuO-exposed Daphnia magna: A TXRF spectroscopy study

Toxicity of Cu and Cu-based nanoparticles (NPs) to aquatic biota is usually mitigated in natural freshwater compared to organics-free artificial freshwater. The main aim of this study was to evaluate whether mitigated toxicity is accompanied by lower total copper body burden in the freshwater crustacean Daphnia magna and whether CuO NPs are more hazardous in this aspect than soluble Cu salts.Total copper body burden in different media (OECD202 artificial freshwater and two natural freshwaters) was measured by a relatively novel technique - total reflection X-ray fluorescence (TXRF) spectroscopy - which proved suitable for the analysis of individual juvenile daphnids. Mean copper body burden was 2.8–42 times higher in daphnids exposed to CuO NPs (0.05 mg Cu/L and 1 mg Cu/L) than in daphnids exposed to equal or equitoxic concentrations (0.025 mg Cu/L and 0.05 mg Cu/L) of CuSO4. Using natural freshwater instead of artificial one resulted in increased copper burden after exposure to CuO NPs but not after exposure to Cu salt. After 24 h post-exposure depuration in the presence of algae Raphidocelis subcapitata, total copper body burden in daphnids exposed to CuO NPs sharply decreased while in daphnids exposed to Cu salt it did not. Despite the CuO NP toxicity mitigating effect of natural freshwater, total copper body burden of aquatic crustaceans in natural waterbodies may be greater than could be predicted based on the results obtained using artificial freshwater as the test medium.

Concentration addition and independent action model: Which is better in predicting the toxicity for metal mixtures on zebrafish larvae

The joint toxicity of chemical mixtures has emerged as a popular topic, particularly on the additive and potential synergistic actions of environmental mixtures. We investigated the 24h toxicity of Cu–Zn, Cu–Cd, and Cu–Pb and 96h toxicity of Cd–Pb binary mixtures on the survival of zebrafish larvae. Joint toxicity was predicted and compared using the concentration addition (CA) and independent action (IA) models with different assumptions in the toxic action mode in toxicodynamic processes through single and binary metal mixture tests. Results showed that the CA and IA models presented varying predictive abilities for different metal combinations. For the Cu–Cd and Cd–Pb mixtures, the CA model simulated the observed survival rates better than the IA model. By contrast, the IA model simulated the observed survival rates better than the CA model for the Cu–Zn and Cu–Pb mixtures. These findings revealed that the toxic action mode may depend on the combinations and concentrations of tested metal mixtures. Statistical analysis of the antagonistic or synergistic interactions indicated that synergistic interactions were observed for the Cu–Cd and Cu–Pb mixtures, non-interactions were observed for the Cd–Pb mixtures, and slight antagonistic interactions for the Cu–Zn mixtures. These results illustrated that the CA and IA models are consistent in specifying the interaction patterns of binary metal mixtures.

The effect of anthropogenic impoundment on dissolved organic matter characteristics and copper binding affinity: Insights from fluorescence spectroscopy

Excitation-emission matrix fluorescence spectroscopy combined with parallel factor analysis (EEM-PARAFAC) and two-dimensional correlation spectroscopy (2D-COS) were applied to evaluate the effects of anthropogenic impoundment on the characteristics of dissolved organic matter (DOM) and its heavy metal binding affinity. Three field-sampling cruises conducted in Hongze Lake from 2015 to 2016 were classified as early impoundment and late impoundment cruises according to the hydrological conditions. Five fluorescence components were derived from EEM-PARAFAC, including three humic-like components (C1C3) and two protein-like components (C4 and C5). The results show a higher dissolved organic carbon concentration, humification degree, molecular size, and level of terrestrial humic-like substances (C1C3) for early impoundment DOM compared with late impoundment DOM, which were derived from the relatively high inflow discharges present before impoundment. Meanwhile, the relatively high autochthonous contribution and level of protein-like substances found in late impoundment DOM suggested that anthropogenic impoundment can influence the DOM composition in Hongze Lake. Increases in the binding affinities (log Km) of humic-like substances (C1 and C3) and decreases in the log Km of tryptophan-like substances (C4) were observed during the impoundment period. Additionally, 2D-COS results suggested that the preferential Cu(II) binding ligands in early and late impoundment DOM were tryptophan- (C4) and humic-like (C1) substances, respectively. These results indicated that impoundment-derived DOM composition alteration can decrease the bioavailability and toxicity of Cu in Hongze Lake. The results reported here will improve the understanding of DOM and heavy metal cycling in impoundment lakes.

Effects of single and combined exposures to copper and benzotriazole on Eisenia fetida

Benzotriazole (BTR), an emerging class of environmental pollutant, is widely used in industrial applications and household dishwashing agents. Despite the reported toxicity of BTR to aquatic organisms, little is known about its effects on terrestrial invertebrates. Copper (Cu) accumulates in agricultural soils receiving urban waste products, fertilizers, fungicides, and urban sewage. In this study, two different types of bioassays (acute toxicity test and behavioral toxicity test) were performed to evaluate the toxicity of Cu and BTR, both singly and together, on the earthworm (Eisenia fetida) in artificial soil. The results of avoidance behaviour tests showed that the EC50,48 h values for Cu and BTR were 1.47 and 0.46 mmol kg−1, respectively. The results of the acute toxicity tests showed that the LC50,7 d and LC50,14 d of Cu in earthworms were 9.19 and 5.28 mmol kg−1, respectively, and the LC50,7 d and LC50,14 d of BTR were 2.43 and 1.76 mmol kg−1, respectively. Toxicity analysis demonstrated that the binary BTR and Cu mixture had predominantly antagonistic effects on the avoidance behaviour and survival of earthworms. The Cu2+ activities and mortality of earthworms decreased significantly with increasing concentrations of BTR, while the solid-liquid distribution coefficient of Cu increased. These results indicated that the presence of BTR can reduce the toxicity as well as the bioavailability of Cu in soil with both BTR and Cu.

Evaluación de la toxicidad de metales pesados en dos suelos agrícolas de Colombia mediante bioensayos

La presente investigación tuvo como objetivo determinar la toxicidad de Cu, Cd, Ni, Pb y Zn, en dos suelos agrícolas colombianos, Andisol y Vertisol, mediante bioensayos con Lactuca sativa y Vibrio fischeri. Los metales se adicionaron individualmente a los suelos hasta superar el nivel de intervención de Andalucía. Posteriormente se incubaron a 25 °C y 60% de humedad, durante 60 y 90 días, respectivamente. El diseño experimental fue un completamente al azar con tres repeticiones. Luego de cada incubación se determinó la concentración de los metales en extractos acuosos, y con ellos se efectuaron bioensayos con Lactuca Sativa y Vibrio fischeri. Se efectuó análisis estadístico de resultados, comparaciones post hoc (Tukey), correlaciones y análisis de componentes principales, para encontrar los factores que afectaron los organismos en estudio. Se encontró que el Vertisol presentó mayor capacidad de inmovilización de los metales, en función de su contenido de arcillas y pH neutro, lo cual se reflejó en menor toxicidad sobre las especies en ensayo, indicando que este suelo actuó como protectante contra la movilidad de contaminantes en solución del suelo. El ensayo con V. fischeri presentó mayor sensibilidad a los contaminantes, permitiendo una mejor discriminación de los niveles de toxicidad. La capacidad de ambos suelos de inhibir la toxicidad se incrementó con el tiempo, posiblemente por interacción de los metales con los diferentes componentes de los suelos, y la disminución de su movilidad por mecanismos como la formación de complejos estables, y se relacionó con el incremento del pH.

Extended biotic ligand model for predicting combined Cu–Zn toxicity to wheat (Triticum aestivum L.): Incorporating the effects of concentration ratio, major cations and pH

Current risk assessment models for metals such as the biotic ligand model (BLM) are usually applied to individual metals, yet toxic metals are rarely found singly in the environment. In the present research, the toxicity of Cu and Zn alone and together were studied in wheat (Triticum aestivum L.) using different Ca2+ and Mg2+ concentrations, pH levels and Zn:Cu concentration ratios. The aim of the study was to better understand the toxicity effects of these two metals using BLMs and toxic units (TUs) from single and combined metal toxicity data. The results of single-metal toxicity tests showed that toxicity of Cu and Zn tended to decrease with increasing Ca2+ or Mg2+ concentrations, and that the effects of pH on Cu and Zn toxicity were related not only to free Cu2+ and Zn2+ activity, respectively, but also to other inorganic metal complex species. For the metal mixture, Cu–Zn interactions based on free ion activities were primarily additive for the different Ca2+ and Mg2+ concentrations and levels of pH. The toxicity data of individual metals derived by the BLM, which incorporated Ca2+ and Mg2+ competition and toxicity of inorganic metal complexes in a single-metal toxicity assessment, could predict the combined toxicity as a function of TU. There was good performance between the predicted and observed effects (root mean square error [RMSE] = 7.15, R2 = 0.97) compared to that using a TU method with a model based on free ion activity (RMSE = 14.29, R2 = 0.86). The overall findings indicated that bioavailability models that include those biochemistry processes may accurately predict the toxicity of metal mixtures.

Sensitivity of the glochidia (larvae) of freshwater mussels (Bivalvia: Unionida: Hyriidae) to cadmium, cobalt, copper, lead, nickel and zinc: Differences between metals, species and exposure time

Freshwater mussels (Bivalvia: Unionida) are among the most threatened freshwater faunal groups worldwide. Metal contamination is one threat that has been linked to declining mussel population distribution and abundance. This study determined the sensitivity (valve closure) of the glochidia (larvae) of six species of Australian freshwater mussels to cadmium (Cd), cobalt (Co), copper (Cu), lead (Pb), nickel (Ni) and zinc (Zn), key metal contaminants impacting urbanized coastal rivers in south-eastern Australia (home to ~50% of the population), in a soft reconstituted freshwater (hardness 42mgCaCO3L−1; alkalinity 22mgCaCO3L−1 and pH7.0) over 72h. The sensitivity of each mussel species to each metal increased 2.5-fold with increasing exposure time from 24 to 72h. The most sensitive mussel species (Cucumerunio novaehollandiae), across all metals and exposure times, was ~60% more sensitive than the least sensitive species (Velesunio ambiguus). The relative sensitivity of glochidia to the six selected metals, across all mussel species and exposure times, was: Cu>Cd>Pb>Co=Ni>Zn. Glochidia were most sensitive to Cu and least sensitive to Zn. Quantitatively, the toxicity of Cu was 3-fold more than Cd, 8-fold more than Pb, 14-fold more than Co or Ni and 16-fold more than Zn. The cell surface binding affinities (conditional log K values) of Cd (range 6.65–6.94), Co (6.04–6.29), Cu (7.17–7.46), Ni (6.02–6.29), Pb (6.24–6.53) or Zn (5.96–6.23), pooled for all mussel species after 72h exposure, were positively related to metal sensitivity. The chronic no effect concentrations (NECs) of Cu, Ni and Zn were below (i.e. glochidia were more sensitive than) their national freshwater guideline values, indicating that freshwater mussels may not be adequately protected for these metals in urbanized coastal rivers within south-eastern Australia.