Eisenia fetida avoidance behavior as a tool for assessing the efficiency of remediation of Pb, Zn and Cd polluted soil

Nano zerovalent Fe did not reduce metal(loid) leaching and ecotoxicity further than conventional Fe grit in contrasting smelter impacted soils: A 1-year field study

The majority of the studies on nanoscale zero-valent iron (nZVI) are conducted at a laboratory-scale, while field-scale evidence is scarce. The objective of this study was to compare the metal(loid) immobilization efficiency of selected Fe-based materials under field conditions for a period of one year. Two contrasting metal(loid) (As, Cd, Pb, Zn) enriched soils from a smelter-contaminated area were amended with sulfidized nZVI (S-nZVI) solely or combined with thermally stabilized sewage sludge and compared to amendment with microscale iron grit. In the soil with higher pH (7.5) and organic matter content (TOC = 12.7 %), the application of amendments resulted in a moderate increase in pH and reduced As, Cd, Pb, and Zn leaching after 1-year, with S-nZVI and sludge combined being the most efficient, followed by iron grit and S-nZVI alone. However, the amendments had adverse impacts on microbial biomass quantity, S-nZVI being the least damaging. In the soil with a lower pH (6.0) and organic matter content (TOC = 2.3 %), the results were mixed; 0.01 M CaCl2 extraction data showed only S-nZVI with sludge as remaining effective in reducing extractable concentrations of metals; on the other hand, Cd and Zn concentrations were increased in the extracted soil pore water solutions, in contrast to the two conventional amendments. Despite that, S-nZVI with sludge enhanced the quantity of microbial biomass in this soil. Additional earthworm avoidance data indicated that they generally avoided soil treated with all Fe-based materials, but the presence of sludge impacted their preferences somewhat. In summary, no significant differences between S-nZVI and iron grit were observed for metal(loid) immobilization, though sludge significantly improved the performance of S-nZVI in terms of soil health indicators. Therefore, this study indicates that S-nZVI amendment of soils alone should be avoided, though further field evidence from a broader range of soils is now required.

Environmental-related doses of afidopyropen induced toxicity effects in earthworms (Eisenia fetida)

Afidopyropen has high activity against pests. However, it poses potential risks to the soil ecology after entering the environment. The toxicity of afidopyropen to earthworms (Eisenia fetida) was studied for the first time in this study. The results showed that afidopyropen had low level of acute toxicity to E. fetida. Under the stimulation of chronic toxicity, the increase of reactive oxygen species (ROS) level activated the antioxidant and detoxification system, which led to the increase of superoxide dismutase (SOD) and glutathione S-transferase (GST) activities. Lipid peroxidation and DNA damage were characterized by the increase of malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) contents. Meanwhile, the functional genes SOD, CAT, GST, heat shock protein 70 (HSP70), transcriptionally controlled tumor protein (TCTP), and annetocin (ANN) played a synergistic role in antioxidant defense. However, the comprehensive toxicity of high concentration still increased on the 28th day. In addition, strong histopathological damage in the body wall and intestine was observed, accompanied by weight loss, which indicated that afidopyropen inhibited the growth of E. fetida. The molecular docking revealed that afidopyrene combined with the surface structure of SOD and GST proteins, which made SOD and GST become sensitive biomarkers reflecting the toxicity of afidopyropen to E. fetida. Summing up, afidopyropen destroys the homeostasis of E. fetida through chronic toxic. These results provide theoretical data for evaluating the environmental risk of afidopyropen to soil ecosystem.

Toxicological effects induced by two carbamates on earthworms (Eisenia fetida): Acute toxicity, arrested regeneration and underlying mechanisms

Eisenia fetida is recognised as advantageous model species in ecotoxicological and regeneration investigations. The intensive utilization of carbamate pesticides (CARs) imposes heavy residue burdens and grave hazards on edaphic environments as well as soil fauna therein. However, precise mechanisms whereby the specific CAR exerted toxic effects on earthworms remain largely elusive, notably from regenerative perspective. Herein, acute responses and regenerative toxicity of two carbamates (metolcarb, MEB and fenoxycarb, FEB) against E. fetida were dissected using biochemical, histological as well as molecular approaches following OECD guidelines at the cellular, tissue and organismal level. The acute toxicity data implied that MEB/FEB were very toxic/medium to extremely toxic, respectively in filter paper contact test and low to medium toxic/low toxic, respectively in artificial soil test. Chronic exposure to MEB and FEB at sublethal concentrations significantly mitigated the soluble protein content, protein abundance while enhanced the protein carbonylation level. Moreover, severely retarded posterior renewal of amputated earthworms was noticed in MEB and FEB treatments relative to the control group, with pronouncedly compromised morphology, dwindling segments and elevated cell apoptosis of blastema tissues, which were mediated by the rising Sox2 and decreasing TCTP levels. Taken together, these findings not only presented baseline toxicity cues for MEB and FEB exposure against earthworms, but also yielded mechanistic insights into regenerative toxicity upon CAR exposure, further contributing to the environmental risk assessment and benchmark formulation of agrochemical pollution in terrestrial ecosystem.

Effects of biochar on earthworms during remediation of potentially toxic elements contaminated soils

With the widespread use of biochar for soil remediation and improvement, its effects on soil organisms are receiving increased attention. The impacts of biochar on earthworms are still poorly understood. This study aimed to assess the potential ecotoxicity of rice husk biochar (RB) and sludge biochar (SB) on earthworms during potentially toxic elements (PTEs) contaminated soil remediation. The results showed that high rates of RB addition (5% and 10%) caused earthworm mortality, but SB addition did not affect earthworm survival. When added at non-lethal rates (3%), RB and SB addition did not affect survival, weight loss, and PTEs accumulation of earthworms, while resulting in apparent avoidance behavior and oxidative stress response. Among them, RB addition was more likely to cause avoidance behavior, while SB addition had a more pronounced stress effect on earthworms. Additionally, the bacterial communities in the earthworm gut were more sensitive to biochar addition than those in soil. SB addition had a greater impact on earthworm gut bacterial communities than RB addition. The addition of RB and SB increased the abundance of Bacillaceae while decreasing the abundance of Rhizobiaceae in the earthworm gut. This change in the composition of bacterial community may impact the nitrogen cycle and organic matter degradation functions of earthworms. The study suggests that RB and SB may have different effects on earthworms during PTEs-contaminated soil remediation, depending on their properties. It will assist us to understand the potential ecotoxicity of biochar and provide several guidance for its safe application.

Assessment Toxicity of Soils from Areas with Mining Activity Through the Stability of the Lysosomal Membrane and Avoidance Behavior in the Earthworm Eisenia fetida

The aim of this study was to determine the effect of soils from areas with mining activity on the stability of the lysosomal membrane and avoidance behavior in the worm Eisenia fetida. Texture, organic material, conductivity and pH were determined in soils. The total concentrations of Cu, Zn, Pb, Ni, As and Hg were determined in tissues of E. fetida and in soils. Neutral red retention time (NRRT) was determined in hemocytes, and behavior with the avoidance test, in the earthworm. Cu (1563 ± 58 mg kg^-1) and Zn (135 ± 9 mg kg^-1) had the highest mean concentrations in the soils, while Hg (0.01 ± 0.001 mg kg^-1) had the lowest concentration in all the soils. The soil with the highest Cu concentration produced an avoidance of > 80%. Most of the soils produced a significant loss of the stability of the lysosomal membrane. The variables organic material and sand would facilitate habitat selection in E. fetida, In conclusion, the soils have chemical agents in bioavailable concentrations that provoke adverse cellular effects and evasion behavior. We propose the use of both response variables as early alerts in the evaluation of soils.

Metsulfuron-methyl induced physiological, behavioural and biochemical changes in exotic (Eisenia fetida) and indigenous (Metaphire posthuma) earthworm species: Toxicity and molecular docking studies

In modern agricultural practices, Metsulfuron-methyl (sulfonylurea herbicide) is widely employed to inhibit the weeds and grasses. The current study revealed that Metaphire posthuma was more sensitive than Eisenia fetida against Metsulfuron-methyl (MSM). The LC₅₀ values for Eisenia fetida were 2884.08 mgkg^-1 and 1871.18 mgkg^-1after 7 and 14 days, respectively. Similarly, the LC₅₀ values for Metaphire posthuma were 2449.34 mgkg^-1 and 1673.10 mgkg^-1for 7 and 14 days, respectively. Reproduction parameters were significantly decreased at 400 (T3), 800 (T4) and 1600 (T5) mgkg^-1 MSM in E. fetida whereas at 200 (T2), 400 (T3), 800 (T4), 1600 (T5) mgkg^-1 MSM in M. posthuma. EC₅₀ of avoidance response for 20% MSM by E. fetida and M. posthuma was recorded 901.76 mgkg^-1and 544.21 mgkg^-1 respectively. Malondialdehyde (MDA) content along with guaiacol peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD) activities were initially increased up to 21st day by MSM, inducing a slight oxidative stress in earthworms and recovered to control level on 28th day. The GST activities were continuously stimulated throughout the exposure period and enhance the detoxification effect thereby preventing the earthworms from toxins. Molecular docking studies indicated that hydrogen bonding and hydrophobic interactions are key forces in binding between MSM and SOD/CAT/POD/GST. As a result, this is the first study to be reported on physiological, behavioural and biochemical changes in two different earthworm species under the exposure of sulfonyl urea herbicide.

Lead and Zinc Uptake and Toxicity in Maize and Their Management

Soil contamination with heavy metals is a global problem, and these metals can reach the food chain through uptake by plants, endangering human health. Among the metal pollutants in soils, zinc (Zn) and lead (Pb) are common co-pollutants from anthropogenic activities. Thus, we sought to define the accumulation of Zn and Pb in agricultural soils and maize. Concentrations of Pb in agricultural soil (in Namibia) could reach 3015 mg/Kg, whereas concentrations of Zn in soil (in China) could reach 1140 mg/Kg. In addition, the maximum concentrations of Zn and Pb were 27,870 and 2020 mg/Kg in maize roots and 4180 and 6320 mg/Kg in shoots, respectively. Recent studies have shown that soil properties (such as organic matter content, pH, cation exchange capacity (CEC), texture, and clay content) can play important roles in the bioavailability of Zn and Pb. We also investigated some of the genes and proteins involved in the uptake and transport of Zn and Pb by maize. Among several amendment methods to reduce the bioavailability of Zn and Pb in soils, the use of biochar, bioremediation, and the application of gypsum and lime have been widely reported as effective methods for reducing the accumulation of metals in soils and plants.

An Investigation into the Growth of Lolium perenne L. and Soil Properties Following Soil Amendment with Phosphorus-Saturated Bauxite Residue

Reuse options for bauxite residue include treatment of phosphorus (P)-enriched wastewaters where the P-saturated media offers fertiliser potential. However, few studies have assessed the impact on soil properties. Two types of spent P-saturated bauxite residue were applied to soil and compared to conventional superphosphate fertiliser as well as a control soil. Soil physico-chemical properties, worm Eisenia fetida L. choice tests, and Lolium perenne L. growth and elemental uptake were examined. Comparable biomass and plant content for L. perenne in the P-saturated bauxite residue treatments and those receiving superphosphate, indicated no phytotoxic effects. E. fetida L. showed a significant preference for the control soil (58 %± 2.1%) over the amended soils, indicating some form of salt stress. Overall, P-saturated bauxite residue was comparable to the superphosphate fertiliser in terms of the plant performance and soil properties, indicating the potential recycling of P from wastewaters using bauxite residue as a low-cost adsorbent.

Toxicity of isoprocarb to earthworms (Eisenia fetida): Oxidative stress, neurotoxicity, biochemical responses and detoxification mechanisms

Isoprocarb (IPC) is a conventional carbamate with high insecticidal activity, however, generalized use of it may cause soil contamination and adversely implicate non-target biota. Following OECD standardized toxicological protocols, the toxic effects of IPC on Eisenia fetida at lethal and sublethal concentrations were examined to elucidate its toxic modes of action as well as biochemical and detoxification responses of E. fetida. Acute toxicity tests showed that IPC induced a concentration-dependent rise of mortality, with LC₅₀ of 8.20 μg/cm² (48 h) in FPCT and 3.37 mg/kg (14 d) in AST, respectively. The ecotoxicological effects of IPC chronic exposure were measured by physiochemical, qRT-PCR and western blot analysis. Specifically, ROS, MDA and 8-OHdG contents were enhanced and T-AOC, SOD, CAT and POD activities diminished with increasing concentrations. While activities of CYP3A4 and CarE as well as expressions of Hsp70, GPx and GST were elevated upon IPC treatments, responsible for detoxifying mechanisms as implied by principal component analysis (PCA). Meanwhile, IPC diminished NRRT and inhibited AChE activities along with expressions of AChE-related genes. All these striking alterations between IPC-exposed earthworms and controls were illustrated in PCA model. More importantly, growth, reproductive and regenerative toxicity of IPC were observed with reduced cast production and soluble protein content, suppressed ANN protein and gene expressions, reversely modulated TCTP and Sox2 gene and protein, respectively. Taken together, deleterious perturbations could be induced by IPC in biophysiological homeostasis of E. fetida primarily through oxidative stress and neural dysfunction. This study not only highlighted potential hazard of IPC to earthworms in the terrestrial ecosystem, but also expounded upon mechanisms underlying toxic modes of action for IPC and detoxification of earthworms.

Application of in situ bioremediation strategies in soils amended with sewage sludges

Increasing soil loss and the scarcity of useful land requires new reusing strategies. Thus, recovery of polluted soils recovery offers a chance for economic and social regeneration. With this objective, different soil cleaning technologies have been developed during the last few decades. On one hand, classical physical and/or chemical technologies can be found which are efficient, but have high costs and impacts upon ecosystems. On the other hand, biological methods (such as phytoremediation, bioremediation and vermiremediation) are relatively cost effective and eco-friendly, but also more time-consuming. These biological methods and their yields have been widely studied but little is known about the interaction between different soil cleaning methods. The combination of different biological strategies could lead to an improvement in remediation performance. Hence, in the present work, different micro-, vermi- and phyto-remediation combinations are applied in a sewage sludge polluted landfill in Gernika-Lumo (Basque Country) which was used as a disposal point for decades, in search of the treatment (single) or combination (dual or triple) of treatments with best remediation yields. Eight experimental groups were applied (n=3) placing earthworms (E), bacteria (B), plants (P), bacteria+earthworms (B+E), bacteria+plants (B+P), plants+earthworms (P+E) plants+bacteria+earthworms (P+B+E) and a non-treated (N.T.) group in the experimental plot (Landfill 17), for 12 months. In order to assess the efficiency of each treatment, a complete characterization (chemical and ecotoxicological) was carried out before and after remediation. Results showed high removal rates for dieldrin (between 50% and 78%) in all the experimental groups. In contrast, removal rates around 20-25% were achieved for heavy metals (Cd 15%-35%; Ni 24%-37%; Pb 15%-33%; Cr 7%-39%) and benzo(a)pyrene (19.5%-28%). The highest reductions were observed in dual (P+E, B+E) and triple (P+B+E) treatments. The best elimination yields were obtained after P+B+E treatment, as highlighted by the battery of ecotoxicological tests and bioassays performed with earthworms, plants and bacteria.

Role of Flavonol Synthesized by Nucleus FLS1 in Arabidopsis Resistance to Pb Stress

Lead (Pb) is an important pollutant of worldwide concern with respect to extensive pollution sources and highly toxic effect. Flavonol can improve plant resistance to abiotic stress and is also responsible for the alleviating effect under Pb stress. The relationship between Pb stress and flavonol and the knowledge about the mechanisms of flavonol function are very limited. Pb affected the energy metabolism process and, thus, inhibited plant growth and development. Flavonol accumulation controlled by FLS1 (flavonol synthase) could alleviate the toxic effect. Importantly, nes (mutant of NES that allows FLS1 to enter the nucleus expression) showed better growth status and lighter oxidative damage than NES (N-terminal nucleus exclusion signal peptide prevents FLS1 from entering the nucleus expression), which indicated that nucleus flavonol synthesized by nucleus FLS1 plays a key role in plant resistance to Pb stress. Although FLS1 signals were detected in the cell membrane, cytoplasm, and nucleus, membrane flavonol, cytoplasm flavonol, and nucleus flavonol were not exercising their function in the corresponding position. The expression of nucleus FLS1 intervened in the total content and composition of flavonol. The results also revealed that nucleus flavonol could regulate the ascorbate metabolism for alleviating the damage on the chloroplast, thus maintaining the photophosphorylation pathway. Our findings provided new insights for the molecular basis of Pb tolerance and response mechanism of the plant.

Appraisal and ranking of poly-aluminium chloride, ferric chloride and alum for the treatment of dairy soiled water

Land spreading of dairy soiled water (DSW) may result in pollution of ground and surface waters. Treatment of DSW through sludge-supernatant separation using chemical coagulants is a potential option to reduce the negative environmental impacts of DSW. The aims of this study were to (1) assess the effectiveness of three chemical coagulants - poly-aluminium chloride (PACl), ferric chloride (FeCl₃) and alum - in improving effluent quality, and (2) assess the properties of the sludge that is generated as by-product from the process for its suitability for land application. Taking into consideration optimum doses to minimize pollutants (turbidity, chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN), and E. coli), optimum mixing times and cost, FeCl₃ was the best performing coagulant. Generated sludges had higher nutrient content and fewer E. coli than raw DSW, and did not display any evidence of phytotoxicity to the growth of Lolium perenne L. using germination tests. The study discussed the results in a sustainable farm management context, and suggested that the effluent (supernatant) from the treatments may be recycled to wash farm yards, saving water. In parallel, the sludge portion can be applied to amend soil properties with no adverse impacts on the grass growth, providing an agronomic value as an organic fertilizer, and reducing the risk of nutrient losses. This management approach could minimize the overall net cost compared to land application of raw DSW.

Higher than … or lower than ….? Evidence for the validity of the extrapolation of laboratory toxicity test results to predict the effects of chemicals and ionising radiation in the field

Single species laboratory tests and associated species sensitivity distributions (SSDs) that utilise the resulting data can make a key contribution to efforts to prospective hazard assessments for pesticides, biocides, metals and ionising radiation for research and regulatory risk assessment. An assumption that underlies the single species based toxicity testing approach when combined in SSD models is that the assessments of sensitivities to chemical and ionising radiation measured across a range of species in the laboratory can inform on the likely effects on communities present in the field. Potential issues with the validity of this assumption were already recognised by Van Straalen and Denneman (1989) in their landmark paper on the SSD methodology. In this work, they identified eight major factors that could potentially compromise the extrapolation of laboratory toxicity data to the field. Factors covered a range of issues related to differences in chemistry (e.g. bioavailability, mixtures); environmental conditions (optimal, variable), ecological (compensatory, time-scale) and population genetic structure (adaptation, meta-population dynamics). This paper outlines the evidence pertaining to the influence of these different factors on toxicity in the laboratory as compared to the field focussing especially on terrestrial ecosystems. Through radiological and ecotoxicological research, evidence of the influence of each factor on the translation of observed toxicity from the laboratory to field is available in all cases. The importance of some factors, such as differences in chemical bioavailability between laboratory tests and the field and the ubiquity of exposure to mixtures is clearly established and has some relevance to radiological protection. However, other factors such as the differences in test conditions (optimal vs sub-optimal) and the development of tolerance may be relevant on a case by case basis. When SSDs generated from laboratory tests have been used to predict chemical and ionising radiation effects in the field, results have indicated that they may often seem to under-predict impacts, although this may also be due to other factors such as the effects of other non-chemical stressors also affecting communities at polluted sites. A better understanding of the main factors affecting this extrapolation can help to reduce uncertainty during risk assessment.

Changes in soil properties after remediation influence the performance and survival of soil algae and earthworm

Previous research on soil remediation focused on soil properties and not on its effects on soil ecosystems. The present study investigated the adverse effects of soil physicochemical changes due to remediation on the biological indicators Chlorococcum infusionum and Chlamydomonas reinhardtii (algae) and Eisenia andrei (earthworm). Soil physicochemical properties, concentrations of total, bioavailable, and water-soluble heavy metals in soil were measured before and after remediation. Changes in soil pH, electrical conductivity, total nitrogen, and total phosphorous immediately after soil remediation were the primary causes of the biomass and photosynthetic activity inhibition observed in C. infusionum and C. reinhardtii, and the survival, normality, and burrowing behavior decrease observed in E. andrei in remediated soils showing dramatic changes in those properties. These findings suggest that remediated soils need some time to recover before restoring their functions, although heavy metals are no longer contaminating the soil.

Antioxidant enzyme activities of Folsomia candida and avoidance of soil metal contamination

Induction of the antioxidant enzymes catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) and the avoidance of potentially toxic metals in soil by Folsomia candida were investigated. Both laboratory-spiked and field-polluted agricultural soils were used. Cadmium (Cd) concentrations in body tissues, animal avoidance behaviour and physico-chemical properties of the field soils were also determined. In laboratory Cd-spiked soils, the CAT and SOD activities in the Cd treatments were 71.1-94.7 and 1.31-4.55 times higher than in the control, respectively. In field-polluted agricultural soils, the CAT and POD activities generally increased with increasing pollution index (PI _Nemerow ) of soil Cd, Cu, Pb and Zn. The CAT, POD and SOD activities at different PI _Nemerow were 65.7-128, 30.1-180 and 36.5-95.8% higher than in the control, respectively. In line with the enzyme activities, Cd concentrations in the animal bodies were 8.31-15.1 and 3.21-10.0 times higher than in the control in spiked and field-polluted soils, respectively. Avoidance behaviour also increased with increasing metal concentrations in both soils. The effects of metals on CAT, POD or SOD activity were influenced by soil properties such as soil texture and pH. These results indicate that the antioxidant enzymes activities of F. candida can be induced by heavy metals and potentially used to assess the toxicity, and also that soil properties must be considered in the analysis of enzyme activities in different types of field soils.

Allelopathic effects of volatile organic compounds from Eucalyptus grandis rhizosphere soil on Eisenia fetida assessed using avoidance bioassays, enzyme activity, and comet assays

Allelopathy has been identified as an underlying mechanism of detrimental environmental impacts within commercial plantations. Eucalyptus spp. are known to generate huge amounts of volatile organic compounds (VOCs) that can function as phytotoxins and thus inhibit other plants. In the present study, biochemical markers, including activities of acetylcholinesterase (AChE) and oxidative stress enzymes, such as superoxide dismutase (SOD) and glutathione S-transferase (GST), were assayed to assess changes in Eisenia fetida at the physiological level induced by different doses of VOCs as part of an acute toxicity test over 7 and 14-day exposures. In addition, the toxicities of VOCs were investigated using a soil avoidance test and comet assay. The results revealed that E. fetida exhibited significant avoidance behavior towards the highest concentrations of undecane, decane, 2,4-dimethyl heptane, and 2,2,4,6,6-pentametyl heptane. The tail DNA percentages were significantly increased for all experimental treatments relative to control. However, under the treatments of VOCs, Olive tail moment content and comet tail length also display an obvious increase compared to control, except for that of octane, undecane and decane treatments. As VOC concentrations and durations increased in the soil, activities of AChE, SOD, and GST were either stimulated or inhibited. Among the VOCs, decane, 2,4-dimethyl heptane, 2,2,4,6,6-pentamethyl heptane, and 2,4-di tert buyl phenol exerted stronger effects on enzymatic activities. In summary, VOCs in rhizosphere soils of E. grandis might exert a toxic impact on E. fetida, among which 2,4-dimethyl heptane, 2,2,4,6,6-pentamethyl heptane, and 2,4-di tert buyl phenol have the strongest effects.

Bioaccumulation and toxic effects of decabromodiphenyl ether in the presence of nanoscale zero-valent iron in an earthworm-soil system

In this study, the bioaccumulation and toxic effects of decabromodiphenyl ether (BDE209) (1 and 10 mg kg^-1) were investigated in the earthworm Eisenia fetida in the presence of different levels of nanoscale zero-valent iron (nZVI) (100, 500, and 1000 mg kg^-1) in an earthworm-soil system. The results demonstrated that compared to single BDE209 exposure, the addition of high levels of nZVI significantly (P < 0.05) inhibited growth and respiration, while increased the avoidance response of earthworms. The perturbations of antioxidant enzyme activities (superoxide dismutase (SOD) and catalase (CAT)) and the malondialdehyde (MDA) content clearly revealed that oxidative stress was induced by the two chemicals. The histopathological observations of the body wall of earthworms under a combined exposure of 10 mg kg^-1 BDE209 with 500 or 1000 mg kg^-1 nZVI illustrated the presence of a serious injury in the intestinal tissues after a 28-day exposure. Additionally, a gas chromatography-mass spectrometry analysis revealed that the coexistence of high level of nZVI significantly (P < 0.05) decreased the bioaccumulation of BDE209 in earthworms; BDE208 and BDE206 were the predominant congeners of debrominated metabolites, and 4,6-dibromobenzene-1,2,3,5-tetraol along with benzene-1,2,4,5-tetraol were determined as the two main intermediates. The possible degradation pathways were proposed on the basis of the identified products. This work provides useful information on the biological effects of BDE209 and nZVI.

Individual and combined toxic effects of herbicide atrazine and three insecticides on the earthworm, Eisenia fetida

In the present study, we evaluated the individual and combined toxic effects of herbicide atrazine and three insecticides (chlorpyrifos, lambda-cyhalothrin and imidacloprid) on the earthworm, Eisenia fetida. Results from 48-h filter paper test indicated that imidacloprid had the highest toxicity to E. fetida with an LC50 of 0.05 (0.041-0.058) μg a.i. cm(-2), followed by lambda-cyhalothrin and atrazine with LC50 values ranging from 4.89 (3.52-6.38) to 4.93 (3.76-6.35) μg a.i. cm(-2), while chlorpyrifos had the least toxicity to the worms with an LC50 of 31.18 (16.22-52.85) μg a.i. cm(-2). Results from 14-days soil toxicity test showed a different pattern of toxicity except that imidacloprid was the most toxic even under the soil toxicity bioassay system. The acute toxicity of atrazine was significantly higher than that of chlorpyrifos. In contrast, lambda-cyhalothrin was the least toxic to the animals under the soil toxicity bioassay system. The binary mixture of atrazine-lambda-cyhalothrin and ternary mixture of atrazine-chlorpyrifos-lambda-cyhalothrin displayed a significant synergistic effect on the earthworms under the soil toxicity bioassay. Our findings would help regulatory authorities understand the complexity of effects from pesticide mixtures on non-target organisms and provide useful information of the interaction of various pesticide classes detected in natural environment.

Assessment of metal toxicity and bioavailability in metallophyte leaf litters and metalliferous soils using Eisenia fetida in a microcosm study

The leaf litters of tree species, Acacia pycnantha (Ap) and Eucalyptus camaldulensis (Ec), predominantly growing at an abandoned copper (Cu) mine and mine soils including controls, were assessed for determining the metal toxicity and bioavailability using earthworm species Eisenia fetida, in a microcosm. Significant reduction in body weight as well as mortality were observed when the worms were introduced into mine soil or its combination with mine Ap litter. Virtually, there were no juveniles when the worms were fed on substratum that contained mine soil or mine leaf litter. The extent of bioaccumulation was dependent on water-soluble fraction of a metal in soil. The accumulation of cadmium, lead and copper in worm tissue was significantly more in treatments that received mine soil with or without mine leaf litter. However, the tissue concentration of zinc did not differ much in earthworms irrespective of its exposure to control or contaminated samples. Mine leaf litter from Ec, a known Cu hyperaccumulator, was more hospitable to earthworm survival and juvenile than that of Ap litter. Validation of the data on bioaccumulation of metals indicated that the mine leaf litter significantly contributed to metal bioavailability. However, it was primarily the metal concentration in mine soil that was responsible for earthworm toxicity and bioavailability. Our data also indicate that detrivores like earthworm is greatly responsible for heavy metal transfer from mines into the ecosystem.

Impacts of BDE209 addition on Pb uptake, subcellular partitioning and gene toxicity in earthworm (Eisenia fetida)

Lead (Pb) and decabromodiphenyl ether (BDE209) are the mainly co-existed contaminants at e-waste recycling sites. The potential toxicity of Pb (250 μg g(-1)) to earthworm Eisenia fetida in the presence of BDE209 (1, 10 and 100 μg g(-1)) was determined during 14-d incubation period. Compared to Pb treatment alone, the co-exposure with 1 μg g(-1) BDE209 barely affected Pb uptake, subcellular partitioning and gene expression; however, histopathological changes in earthworms' body wall (epidermal, circular and longitudinal muscles) demonstrated that 10 and 100 μg g(-1) BDE209 additions enhanced Pb uptake and altered its subcellular partitioning, indicating that Pb redistributed from fractions E (cell debris) and D (metal-rich granules) to fraction C (cytosols); Additionally, BDE209 supply significantly inhibited (p<0.05) the induction of SOD (superoxide dismutase) and CAT (catalase) gene expressions (maximum down-regulation 59% for SOD gene at Pb+100 μg g(-1) BDE209 and 89% for CAT gene at Pb+10 μg g(-1) BDE209), while facilitated (p<0.05) Hsp90 (heat shock protein 90) gene expression with maximum induction rate of 120% after exposure to Pb+10 μg g(-1) BDE209. These findings illustrate the importance of considering environmental BDE209 co-exposure when assessing Pb bioaccumulation and toxicity in multi-contaminated soil ecosystems.

Assessment of the bioavailability and toxicity of lead polluted soils using a combination of chemical approaches and bioassays with the collembolan Folsomia candida

Understanding bioavailability and toxicity is essential for effective ecological assessment of contaminated soils. Total, water and 0.01 M CaCl2 extractable and porewater Pb concentrations and soil properties in different shooting field soils were investigated. Three artificial soils containing different pH and organic matter contents and two natural soils were included as controls. Survival, reproduction and avoidance responses of Folsomia candida exposed to these soils as well as internal Pb concentrations were measured. In the shooting range soils, total Pb concentrations were 47-2,398 mg/kg dw, [Formula: see text] 3.2-6.8 and organic matter content 3.8-7.0%. Pb concentrations in F. candida linearly increased with increasing Pb concentrations in the soils. Acid forest soils caused significantly higher collembolan mortality and avoidance responses and significantly lower reproduction than the neutral grassland soils, which could be attributed to differences in pH and especially CaCl2 extractable Pb concentrations. Soil properties significantly affected bioavailability and toxicity of Pb, but overall the collembolans seemed more sensitive to pH than to Pb in soils. This study shows the importance of selecting proper reference soils for assessing the effects of field soils.

Biomarker responses in earthworm Eisenia andrei exposed to pirimiphos-methyl and deltamethrin using different toxicity tests

The effects of two widely used insecticides - organophosphate pirimiphos-methyl and pyrethroid deltamethrin - were investigated under laboratory conditions following OECD guidelines using the epigeic earthworm Eisenia andrei as the test organism. The overall aim of this study was to evaluate the effects of these pesticides on molecular biomarkers of earthworm E. andrei using the in vitro, filter paper contact and artificial soil test. In this study for the first time the equivalent concentrations of investigated pesticide applied in different tests were calculated. Although the response of measured molecular biomarkers in different toxicity tests had certain similarities, some distinct differences were also evident. Both pesticides inhibited AChE and CES activities in all three applied toxicity tests; however only in the filter paper test the hormetic effect was recorded. The artificial soil test showed that duration of the exposure significantly changed the effects of the investigated pesticides on CAT and GST activities. Namely, after the initial increase, the prolongation of exposure caused the reduction of the CAT and GST activities. Both pesticides significantly inhibited the efflux pump activity. In the artificial soil test, the significant changes in measured biomarkers after application of doses lower than doses recommended for use in the agriculture indicate that the investigated pesticides could have a harmful effect on earthworms in the context of the realistic environment.

Toxicity assessment of 45 pesticides to the epigeic earthworm Eisenia fetida

This study was conducted to investigate comparative toxicity of 45 pesticides, including insecticides, acaricides, fungicides, and herbicides, toward the epigeic earthworm Eisenia fetida. Results from a 48-h filter paper contact test indicated that clothianidin, fenpyroximate, and pyridaben were supertoxic to E. fetida with LC(50) values ranging from 0.28 (0.24-0.35) to 0.72 (0.60-0.94) μg cm(-2), followed by carbaryl, pyridaphenthion, azoxystrobin, cyproconazole, and picoxystrobin with LC(50) values ranging from 2.72 (2.22-0.3.19) to 8.48 (7.38-10.21) μg cm(-2), while the other pesticides ranged from being relatively nontoxic to very toxic to the worms. When tested in artificial soil for 14 d, clothianidin and picoxystrobin showed the highest intrinsic toxicity against E. fetida, and their LC(50) values were 6.06 (5.60-6.77) and 7.22 (5.29-8.68) mg kg(-1), respectively, followed by fenpyroximate with an LC(50) of 75.52 (68.21-86.57) mgkg(-1). However, the herbicides fluoroglycofen, paraquat, and pyraflufen-ethyl exhibited the lowest toxicities with LC(50) values>1000 mg kg(-1). In contrast, the other pesticides exhibited relatively low toxicities with LC(50) values ranging from 133.5 (124.5-150.5) to 895.2 (754.2-1198.0) mg kg(-1). The data presented in this paper provided useful information for evaluating the potential risk of these chemicals to soil invertebrates.

Combined toxicity of cadmium and lead on the earthworm Eisenia fetida (Annelida, Oligochaeta)

Cadmium (Cd) and lead (Pb) in soil have received extensive attention due to their potential toxicological effects. This study analyzed the combined toxicity of Cd and Pb on the earthworm Eisenia fetida. Cellulase activity and DNA damage were chosen as toxic endpoints. Factorial analysis was applied to identify the interaction of Cd and Pb. The results showed that single Pb and Cd could increase the cellulase activity and DNA damage of coelomocytes. The combination of both metals could significantly inhibit cellulase activity. For low Cd concentration, the addition of Pb could increase the DNA damage. However, for high Cd concentration, Pb could decrease the DNA damage. Factorial analysis showed that the changes of Cd concentrations exerted the highest influence on the combined toxicity, followed by factor "Cd*Pb" and "Pb". The combined toxicological effects between Cd and Pb were complex, which might be influenced by the competition adsorption of both metals in soil and biomembrane and their bioavailability. The results of this study are useful for understanding of combined toxicity of Cd and Pb on terrestrial invertebrates.

Comparative acute toxicity of twenty-four insecticides to earthworm, Eisenia fetida

In this study, we used two different types of bioassay, a contact filter paper toxicity bioassay and a soil toxicity bioassay, to compare the acute toxicity of twenty-four insecticides belonging to six chemical categories on earthworm species, Eisenia fetida. Results of the contact filter paper toxicity bioassay indicated that neonicotinoids were super toxic to E. fetida (48 h-LC(50) value ranged from 0.0088 to 0.45 μg cm(-2)), pyrethroids were very toxic (48 h-LC(50) values ranged from 10.55 to 25.7 μg cm(-2)) and insect growth regulators (IGRs) were moderately toxic (48 h-LC(50) values ranged from 117.6 to 564.6 μg cm(-2)) to the worms. However, antibiotics, carbamates and organophosphates induced variable toxicity responses in E. fetida, and were very to extremely toxic (48 h-LC(50) values ranged from 3.64 to 75.75 μg cm(-2)). Results of the soil toxicity bioassays showed a different pattern of toxicity except that neonicotinoids were the most toxic even under the soil toxicity bioassay system. The acute toxicity of neonicotinoids was higher than those of antibiotics, carbamates, IGRs and organophosphates. In contrast, pyrethroids were the least toxic to the worms under the soil toxicity bioassay system. It was concluded that irrespective of bioassay systems, earthworms were more susceptible to neonicotinoids than other modern synthetic insecticides.

A contribution towards the risk assessment of soils from the São Domingos Mine (Portugal): chemical, microbial and ecotoxicological indicators

This study is a contribution towards a risk assessment of the São Domingos Mine area (Portugal), integrating information from: soil physicochemical characteristics, pseudo-total and bioavailable trace elements (As, Cd, Cr, Cu, Ni, Pb and Zn), ecotoxicological evaluation, and microbial indicators. The bioassays using soil eluates (seed germination, luminescent inhibition of Vibrio fischeri and Daphnia magna immobilization) confirmed the soil toxicity categorization obtained with the bioassays using soil (plant growth tests, Eisenia fetida mortality and avoidance behaviour). However, the soil identified as the most toxic using bioassays, was different from the expected when considering the results from pseudo-total and effective bioavailable trace elements. Taking in consideration the observations, it is highly recommended to complement the results from environmental chemistry with results from bioassays, in order to provide a more complete and relevant information on the bioavailability of contaminants and to characterize the risk of contaminated soils.