Effect of time and mode of depuration on tissue copper concentrations of the earthworms Eisenia andrei, Lumbricus rubellus and Lumbricus terrestris

Metaphire guillelmi exhibited predominant capacity of arsenic efflux

Earthworm could regulate their body concentration of arsenic via storage or excretion, and the ability of As efflux among different earthworms is not consistent. Here, whole and semi As exposure patterns with 0-10-30-60-100 mg kg-1 exposure concentrations were set to characterize the As efflux in geophagous earthworm, Metaphire guillelmi. Cast As (As-C) and earthworms' antioxidative responses were monitored to explore the efflux mechanisms under 30 mg kg-1 As-spiked soil (As30), besides, As concentration in earthworm tissue after egestion and dissection depurations were compared. In the whole exposure pattern, As concentration in gut content (As-G, 19.2-120.3 mg kg-1) surpassed that in the tissue (As-T, 17.2-53.2 mg kg-1), and they both increased with exposure concentrations. With the prolong time, they firstly increased and kept stable between day 10-15, then As-G increased while As-T decreased between day 15-20. In the semi-exposure pattern, both As-G and As-T decreased when M. guillelmi was transferred to clean soil for 5 days. During the 42-day incubation in As30, the antioxidative responses including reactive oxygen species (ROS), glutathione (GSH) and glutathione-S-transferase (GST) were firstly increased and then decreased, and As-C (13.9-43.9 mg kg-1) kept higher than As-G (14.2-35.1 mg kg-1). Significantly positive correlations were found between As-T and GSH, As-C and GST. Moreover, tissue As after dissection (11.6-22.9 mg kg-1) was obviously lower than that after egestion (11.4-26.4 mg kg-1), but significantly related to ROS and GSH. Taken together, M. guillelmi exhibited excellent capacity of As efflux, and GSH explained tissue As accumulation while GST facilitated the As elimination via cast. Besides, dissection instead of egestion revealed the As efflux in M. guillelmi more accurately. These findings contributed to a better understanding of how geophagous earthworm M. guillelmi regulated tissue As accumulation for As stress tolerance, and recommended an optimal depuration mode to characterize As accumulation.

Earthworm lipid content and size help account for differences in pesticide bioconcentration between species

The uptake and elimination kinetics of pesticides from soil to earthworms are important in characterising the risk of pesticides to soil organisms and the risk from secondary poisoning. However, the understanding of the relative importance of chemical, soil, and species differences in determining pesticide bioconcentration into earthworms is limited. Furthermore, there is insufficient independent data in the literature to fully evaluate existing predictive bioconcentration models. We conducted kinetic uptake and elimination experiments for three contrasting earthworm species (Lumbricus terrestris, Aporrectodea caliginosa, Eisenia fetida) in five soils using a mixture of five pesticides (log Kow 1.69 - 6.63). Bioconcentration increased with pesticide hydrophobicity and decreased with soil organic matter. Bioconcentration factors were comparable between earthworm species for hydrophilic pesticides due to the similar water content of earthworm species. Inter-species variations in bioconcentration of hydrophobic pesticides were primarily accounted for by earthworm lipid content and specific surface area (SSA). Existing bioconcentration models either failed to perform well across earthworm species and for more hydrophilic compounds (log Kow < 2) or were not parameterised for a wide range of compounds and earthworm species. Refined models should incorporate earthworm properties (lipid content and SSA) to account for inter-species differences in pesticide uptake from soil.

Earthworm-mediated nitrification and gut digestive processes facilitate the remobilization of biochar-immobilized heavy metals

Earthworms and biochar tend to have opposite effects on heavy metal bioavailability in soil. However, the influence and controlling process of earthworms on the immobilisation effect of biochar remain poorly understood. Through the co-cultivation of earthworms with rice-husk biochar and sludge biochar in heavy metal-contaminated soil and desorption experiments involving simulated earthworm gut, we explored the factors that earthworms influence the heavy metal immobilisation ability of biochar. Our results showed that rice-husk biochar and sludge biochar effectively immobilized heavy metals in soil, whereas earthworm activity mobilised heavy metals in biochar-treated soil, which weakens the immobilisation of biochar. The soil pH reduction effect of earthworms by increasing the abundance of soil ammonia-oxidising bacteria to promote soil nitrification is an important mechanism through which earthworms mobilise heavy metals; however, this process did not occur within 10 days of incubation. Nitrification inhibitors effectively inhibit the mobilisation of heavy metals in soil by earthworms. In addition, the bioavailability of heavy metals in earthworm casts was significantly higher than those in the surrounding soil and earthworm-free soil. Moreover, simulated earthworm gut fluid promoted the re-release of heavy metals from the soil and biochar particles. These results suggest that the gut digestion of earthworms is another important mechanism by which earthworms mobilise soil heavy metals and weaken the immobilisation of biochar. Therefore, earthworms weakened the immobilisation effect of biochar mainly by promoting nitrification to reduce soil pH and through gut digestion.

Dissemination of antibiotics through the wastewater-soil-plant-earthworm continuum

Under the ongoing climate change scenario, treated municipal wastewater (TMW) is a potential candidate for irrigated agriculture but may result in the exposure of agricultural environments to antibiotics. We studied the transfers of trimethoprim, sulfamethoxazole, and sulfapyridine in the TMW-soil-plant-earthworm continuum under greenhouse/laboratory conditions. Irrigation of potted spinach and radish with as-collected TMW resulted in no transfers of antibiotics into soil or plants owing to their low concentrations in the tertiary-treated TMW. However, TMW spiked with higher antibiotic concentrations led to transfers through this continuum. High initial inputs, slow soil degradation, and chemical speciation of the antibiotics, coupled with an extensive plant-root distribution, were important factors enhancing the plant uptake of antibiotics. In microcosm studies, transfers from vegetable materials into earthworms were low but showed potential for bioaccumulation. Such food chain transfers of antibiotics may be a driver for antibiotic resistance in agricultural systems, which is an area worthy of future study. These issues can perhaps be mitigated through high levels of TMW purification to effectively remove antibiotic compounds.

Excretion characteristics of nylon microplastics and absorption risk of nanoplastics in rats

Ingestion of environmental microplastics (MPs) by animals is receiving a great health concern, because of its potential adverse effects on organisms. Most ingested MPs will be excreted, while the health threats depend largely on the excretory dynamics. Although the excretion characteristics of MPs in invertebrates and fishes have been studied, information on the excretion of MPs in mammals remains lacking, especially for the fibrous MPs. Here, fibrous and granular MP and nanoplastic (NP) of nylon polymer (polyamide 66, PA66) were exposed in rats by oral in the first day, then the excretion behavior of ingested PA66 in rats was quantified using mass quantification of liquid chromatography with tandem mass spectrometry (LC-MS-MS) together with the microscope observation. Although most of the ingested PA66-MP or PA66-NP was excreted within 48 h, the three forms of PA66 were not completely cleared by the rats even after seven days excretion. The excretion of PA66 in rats was well-described by a first-order kinetics model, and the calculated half-lives of elimination of PA66 polymer in rats are 19.9 h (fibrous PA66-MP), 23.7 h (granular PA66-MP), and 36.9 h (PA66-NP), indicating rats excrete smaller MPs more slowly than the bigger ones. This was further confirmed by the particle size distribution of granular PA66-MP observed in feces. Besides, approximately 30% of the ingested PA66-NP were failed to be detected in feces, while the occurrence of PA66-NP in rat serum induced by PA66-NP ingestion was found. This indicates that PA66-NP can pass through the gut barrier and entered the blood circulation. Therefore, the health risks of ingested MPs, especially for the NPs, deserve further attention.

Earthworms' Degradable Bioplastic Diet of Polylactic Acid: Easy to Break Down and Slow to Excrete

Microplastics (MPs) in soils may be ingested by terrestrial animals. While the application of bioplastics is increasing, the ingestion and excretion characteristics of bio-MPs by terrestrial animals are poorly understood as compared to fossil-MPs. Here, the approach-avoidance behavior of adult earthworms Eisenia fetida to MP-contaminated soil was assessed. Fossil-based poly(ethylene terephthalate) (PET) and bio-based poly(lactic acid) (PLA) MPs were found to be preferred by the earthworms, which might be due to the odor of polymer monomers. MPs in earthworm casts were analyzed by microscopy counting and liquid chromatography-tandem mass spectrometry. The amount of microscopically recognizable excreted PET and PLA was 553 and 261 items/g, respectively, while a higher proportion of smaller PLA particles also presented. Bio-based PLA is much easy to break down by earthworms than fossil-based PET. Submicron and nanocron PLA accounted for 57 and 13% of the excreted PLA on the 10th day of excretion. MP excretion was well described with the first-order kinetic model, and the elimination half-life was 9.3 (for PET) and 45 h (for PLA). A longer excretion period of PLA may be related to its potential to break down in the earthworms' digestive tract. This not only promotes the environmental degradation of PLA but also suggests the ecological risk caused by nanoparticles.

Earthworms ingest microplastic fibres and nanoplastics with effects on egestion rate and long-term retention

Microplastic fibres (MPFs) and nanoplastics (NPs) have the potential to be hazardous to soil organisms. Understanding uptake into organisms is key in assessing these effects, but this is often limited by the analytical challenges to quantify smaller-sized plastics in complex matrices. This study used MPFs and NPs containing inorganic tracers (In, Pd) to quantify uptake in the earthworm Lumbricus terrestris. Following seven days exposure, tracer concentrations were measured in earthworms and faeces. Earthworms exposed to 500 μg MPFs/g soil retained an estimated 32 MPFs in their tissues, while at 5000 μg MPFs/g earthworms retained between 2 and 593 MPFs. High variation in body burdens of MPFs was linked to soil retention in earthworms and reduced faeces production, suggesting egestion was being affected by MPFs. NPs uptake and elimination was also assessed over a more extended time-period of 42 days. After 1 day, NPs were no longer detectable in faeces during the elimination phase. However, some retention of NPs in the earthworms was estimated, not linked to retained soil, indicating not all NPs were eliminated. MPFs and NPs uptake can be quantified in earthworms and both particle types can be retained beyond the depuration period, suggesting the potential for longer-term accumulation.

Impact of Eisenia fetida earthworms and biochar on potentially toxic element mobility and health of a contaminated soil

This study aimed to evaluate the influence of Eisenia fetida (Savigny), added to an acidic soil contaminated with potentially toxic elements (PTEs; As, Sb, Cd, Pb, Zn) and amended with a softwood-derived biochar (2 and 5% w/w), on the mobility of PTEs and soil health (i.e. nutrient availability, enzyme activity and soil basal respiration). The PTEs bioaccumulation by E. fetida and the acute ecotoxicity effects of the amended soils were also evaluated. The interaction between earthworms and biochar led to a significant increase in soil pH, organic matter, dissolved organic carbon content, cation exchange capacity, and exchangeable Ca compared to the untreated soil. Moreover, the water-soluble and readily exchangeable PTE fraction decreased (with the exception of Sb) between 1.2- and 3.0-fold in the presence of biochar and earthworms. Earthworms, biochar, and their combination, led to a reduction of phosphomonoesterase activity which in soils amended with biochar and earthworms decreased between 2.2- and 2.5-fold with respect to the untreated soil. On the other hand, biochar and earthworms also enhanced soil basal respiration and protease activity. Although the survival rate and the weight loss of E. fetida did not change significantly with the addition of 2% biochar, adding the highest biochar percentage (5%) resulted in a survival rate that was ~2-fold lower and a weight loss that was 2.5-fold higher than the other treatments. The PTE bioaccumulation factors for E. fetida, which were less than 1 for all elements (except Cd), followed the order Cd > As>Zn > Cu > Pb > Sb and were further decreased by biochar addition. Overall, these results highlight that E. fetida and biochar, especially at 2% rate, could be used for the restoration of soil functionality in PTE-polluted environments, reducing at the same time the environmental risks posed by PTEs, at least in the short time.

Nanoplastic Transport in Soil via Bioturbation by Lumbricus terrestris

Plastic pollution is increasingly perceived as an emerging threat to terrestrial environments, but the spatial and temporal dimension of plastic exposure in soils is poorly understood. Bioturbation displaces microplastics (>1 μm) in soils and likely also nanoplastics (<1 μm), but empirical evidence is lacking. We used a combination of methods that allowed us to not only quantify but to also understand the mechanisms of biologically driven transport of nanoplastics in microcosms with the deep-burrowing earthworm Lumbricus terrestris. We hypothesized that ingestion and subsurface excretion drives deep vertical transport of nanoplastics that subsequently accumulate in the drilosphere, i.e., burrow walls. Significant vertical transport of palladium-doped polystyrene nanoplastics (diameter 256 nm), traceable using elemental analysis, was observed and increased over 4 weeks. Nanoplastics were detected in depurated earthworms confirming their uptake without any detectable negative impact. Nanoplastics were indeed enriched in the drilosphere where cast material was visibly incorporated, and the reuse of initial burrows could be monitored via X-ray computed tomography. Moreover, the speed of nanoplastics transport to the deeper soil profile could not be explained with a local mixing model. Earthworms thus repeatedly ingested and excreted nanoplastics in the drilosphere calling for a more explicit inclusion of bioturbation in nanoplastic fate modeling under consideration of the dominant mechanism. Further investigation is required to quantify nanoplastic re-entrainment, such as during events of preferential flow in burrows.

Applicability of Enchytraeus bulbosus as a model species in ecotoxicology and risk assessment

Enchytraeus bulbosus is listed in the ISO and OECD standard guidelines as a possible test species of enchytraeid. However, in contrast to other listed species, its applicability in ecotoxicological studies as well as its sensitivity is widely unknown. Therefore, copper, pentachlorophenol(PCP), carbendazim, and chloroacetamide have been investigated by performing two-generation studies with multiple endpoints. Comparable toxicity trends to the existing studies were shown for copper and PCP in the two-generation studies of E. bulbosus. Dose-related abnormal swelling of clitella were found for the first time with PCP and chloroacetamide treatments. Sensitivity comparisons of E. bulbosus to other terrestrial test species were also conducted. E. bulbosus showed high sensitivity, it has comparable sensitivity as other sensitive species of genus Enchytraeus ( E. albidus or E. luxuriosus)to different chemicals, and was more sensitive than E. crypticus and earthworm species ( Eisenia fetida or Eisenia andrei). Combined with the phylogenetic and biological characterization, the results lead to the conclusion that E.bulbosus is a suitable model species in ecotoxicology and the chemical risk assessment (especially in multi-generation) because it has a short generation time, comparatively moderate fecundity, ideal and reasonable sensitivity.

Soil invertebrate toxicity and bioaccumulation of nano copper oxide and copper sulphate in soils, with and without biosolids amendment

The fate, toxicity and bioaccumulation of copper oxide nanoparticles (nCuO) was investigated in soil, with and without biosolids amendment, through chronic exposures using the earthworm, Eisenia andrei, and the collembolan, Folsomia candida. The effects of copper sulphate (CuSO₄) were included so as to compare the behavior of nCuO to a readily soluble counterpart. The fate of nCuO was evaluated through characterization of dissolved and nano-particulate fractions (via single particle ICP-MS) as well as extractable Cu²⁺ throughout the duration of select tests. Neither Cu form was particularly toxic to F. candida, but effects on E. andrei reproduction were significant in all treatments (IC50 range: 98 - 149 mg Cu kg^-1 dry soil). There were no significant differences in toxicity between the Cu forms, nor in extractable Cu²⁺ activities, indicative that particle dissolution within the soil and, subsequent activity of Cu²⁺ was likely the primary mode of toxicity in the nCuO exposures. The presence of biosolids did not significantly alter toxicity of nCuO, but did affect Cu²⁺ activity over time. Bioaccumulation of total Cu in E. andrei when exposed to nCuO (kinetic bioaccumulation factor (BAF_k): 0.80 with biosolids and 0.81 without) was lower than exposure to CuSO₄ (BAF_k: 2.31 with biosolids and 1.12 without). Enhanced dark-field hyperspectral imaging showed accumulation of nCuO along the epidermis and gut of E. andrei, with trace amounts observed in muscle and chloragogenous tissue, providing evidence of nCuO translocation within the organism. The present study demonstrates that the current risk assessment approach for trace metals in the environment, based on substance solubility and bioavailability of the dissolved free ion, are applicable for nCuO exposure to soil invertebrates, but that the rate of particle dissolution in different soil environments is an important factor for consideration.

Different effects of Zn nanoparticles and ions on growth and cellular respiration in the earthworm Eisenia andrei after long-term exposure

In this study, the effects of zinc nanoparticles (ZnO-NPs) and ions (ZnCl₂) on the mortality, growth, maturation, and cellular respiration of the earthworm Eisenia andrei were assessed. Earthworms were individually exposed for 98 days, starting from the juvenile stage, to soils contaminated with either ZnO-NPs or ZnCl₂ (125, 250, 500 and 1000 mg Zn kg^-1 dry weight (dw)). Exposure to the highest-concentration ionic treatments (500 and 1000 mg kg^-1) caused 100% mortality, while for other treatments, mortality did not exceed 15% at the end of exposure. Compared to the control treatment, both 125-1000 mg kg^-1 ZnO-NPs and 125 or 250 mg kg^-1 ZnCl₂ stimulated earthworm growth, which might be due to a hormetic effect. ZnO-NPs and ZnCl₂ caused different responses at medium Zn concentrations (250 and 500 mg kg^-1): earthworms exposed to ionic treatment at 250 mg kg^-1 were characterized by a significantly lower growth constant, lower cellular respiration rate, later inflection point, and higher final body weight than those exposed to ZnO-NPs treatments at the same (250 mg kg^-1) or twice as high (500 mg kg^-1) nominal Zn concentrations. However, differences were not observed in all examined parameters between the studied forms when the highest-concentration ZnO-NPs treatment was compared with the lowest-concentration ionic treatment, which was likely due to the same levels of available Zn concentrations in those treatments. Overall, different growth and maturation strategies accompanied by pronounced differences in cellular respiration were adopted by earthworms exposed to low and medium levels of either ZnO-NPs or ZnCl₂.

Ecotoxicological assessments of biochar additions to soil employing earthworm species Eisenia fetida and Lumbricus terrestris

Biochar is the degradation-resistant product generated by the pyrolysis of organic materials and is produced for the intended use of land application in order to promote carbon sequestration and soil improvement. However, despite the many potential benefits biochar application offers, it is important to quantify any ecological impacts that may result from soil amendment in order to avoid potentially causing negative effects upon soil biota which are crucial in the many ecosystem services provided by soil. Any impacts on earthworms in particular are important to evaluate because of their pivotal role in organic matter breakdown, nutrient cycling and soil formation. In this study, we conducted a series of ecotoxicological assays to determine lethal and sublethal (avoidance, mass change and moisture content) effects of heavy biochar applications that reflect levels that may be used in soil restoration efforts. Two earthworm species, Eisenia fetida, an epigeic species, and Lumbricus terrestris, an anecic species, were utilised as test organisms. Two types of biochar, produced from wheat straw and rice husk feedstocks, respectively, were applied to OECD artificial soil and to a natural soil (Kettering loam) at rates of up to 20% w/w. The influence of biochar application on soil porewater chloride, fluoride and phosphate concentrations was also assessed. The biochar applications induced only a subtle level of avoidance behaviour while effects on survival over a 4-week exposure period were inconsistent. However, death and physical damage to some individual earthworms at high biochar application rates were observed, the mechanisms and processes leading to which should be investigated further. Earthworm development (mean mass change over time) proved to be a more sensitive measure, revealing negative effects on L. terrestris at 10% and 20% (w/w) wheat biochar applications in OECD soil and at 20% (w/w) applications of both biochars in Kettering loam. The moisture content of E. fetida remained remarkably consistent across all treatments (~ 82%), indicating that this is not a sensitive measure of effects. The high rates of biochar application resulted in increased chloride (2 to 3-fold) and phosphate (100-fold) concentrations in simulated soil porewaters, which has important implications for soil fertility and production but also for environmental management.

Phytoremediation efficacy assessment of polycyclic aromatic hydrocarbons contaminated soils using garden pea (Pisum sativum) and earthworms (Eisenia fetida)

Endpoint assessment using biological systems in combination with the chemical analysis is important for evaluating the residual effect of contaminants following remediation. In this study, the level of residual toxicity of polycyclic aromatic hydrocarbons (PAHs) after 120 days of phytoremediation with five different plant species:- maize (Zea mays), Sudan grass (Sorghum sudanense), vetiver (Vetiveria zizanioides), sunflower (Helianthus annuus) and wallaby grass (Austrodanthonia sp.) has been evaluated by ecotoxicological tests such as root nodulation and leghaemoglobin assay using garden pea (Pisum sativum) and acute, chronic and genotoxicity assays using earthworm (Eisenia fetida). The phytoremediated soil exhibited lesser toxicity supporting improved root nodulation and leghaemoglobin content in P. sativum and reducing DNA damage in E. fetida when compared to contaminated soil before remediation. Also, the results of the ecotoxicological assays with the legume and earthworm performed in this study complemented the results obtained by the chemical analysis of PAHs in phytoremediated soil. Therefore, these findings provide a basis for a framework in which remediation efficacy of PAHs-contaminated sites can be evaluated effectively with simple ecotoxicological bioassays using legumes and earthworms.

Polyester-derived microfibre impacts on the soil-dwelling earthworm Lumbricus terrestris

Microplastic (MP) pollution is everywhere. In terrestrial environments, microfibres (MFs) generated from textile laundering are believed to form a significant component of MPs entering soils, mainly through sewage sludge and compost applications. The aim of this study was to assess the effect of MFs on a keystone soil organism. We exposed the earthworm Lumbricus terrestris to soil with polyester MFs incorporated at rates of 0, 0.1 and 1.0 %w/w MF for a period of 35 days (in the dark at 15 °C; n = 4 for each treatment). Dried plant litter was applied at the soil surface as a food source for the earthworms. We assessed earthworm vitality through mortality, weight change, depurate production and MF avoidance testing. In addition, we measured stress biomarker responses via the expression of metallothionein-2 (mt-2), heat shock protein (hsp70) and superoxide dismutase (sod-1). Our results showed that exposure and ingestion of MFs (as evidenced by subsequent retrieval of MFs within earthworm depurates) were not lethal to earthworms, nor did earthworms actively avoid MFs. However, earthworms in the MF1.0% treatment showed a 1.5-fold lower cast production, a 24.3-fold increase in expression of mt-2 (p < 0.001) and a 9.9-fold decline in hsp70 expression (p < 0.001). Further analysis of soil and MF samples indicated that metal content was not a contributor to the biomarker results. Given that burrowing and feeding behaviour, as well as molecular genetic biomarkers, were modulated in earthworms exposed to MFs, our study highlights potential implications for soil ecosystem processes due to MF contamination.

Determination of the carrot (Daucus carota L.) yields parameters by vermicompost and earthworms (Eisenia foetida)

The impact of different types of vermicomposts as well as different species and genera of earthworms on the quantity of the cultivated crops yield has been studied for decades. There is scarce information about the effects of these factors on the quality of plant production. One of the qualitative parameters of vegetables, to which a special attention is paid, is the content of antioxidants (vitamin C, total polyphenols and other substances). The pot experiment carried out in the vegetation cage studied: A) the influence of soil itself, soil mixed with vermicompost in a ratio of 4:1; B) the influence of earthworms number (genus Eisenia foetida, 10 and 20 individuals per pot) supplied to soil mixed with vermicompost in a ratio of 4:1 on the weight of radish roots and leaves, to the total chlorophylls content in leaves, to the selected qualitative parameters of the roots and leaves (vitamin C, total polyphenols content,  total antioxidant activity). The results showed that the supplementation of vermicompost into soil increased the content of the total chlorophylls in leaves. The carrot roots and leaves yield has also been risen. In the roots the content of vitamin C and content of total polyphenols (TPC) was decreased and the total antioxidant activity (TAA) dropped, too. The increased content of vitamin C and TPC was detected in leaves. The inoculation of soil containing vermicompost by earthworms increased the root yield and TAA in roots. It increased the content of vitamin C and TPC in leaves. From the viewpoint of antioxidant content (vitamin C and total polyphenols) the leaves are more attractive than a root. 

Plastic Bag Derived-Microplastics as a Vector for Metal Exposure in Terrestrial Invertebrates

Microplastics are widespread contaminants in terrestrial environments but comparatively little is known about interactions between microplastics and common terrestrial contaminants such as zinc (Zn). In adsorption experiments fragmented HDPE bags c. one mm² in size showed similar sorption characteristics to soil. However, when present in combination with soil, concentrations of adsorbed Zn on a per mass basis were over an order of magnitude lower on microplastics. Desorption of the Zn was minimal from both microplastics and soil in synthetic soil solution (0.01 M CaCl₂), but in synthetic earthworm guts desorption was higher from microplastics (40-60%) than soil (2-15%), suggesting microplastics could increase Zn bioavailability. Individual Lumbricus terrestris earthworms exposed for 28 days in mesocosms of 260 g moist soil containing 0.35 wt % of Zn-bearing microplastic (236-4505 mg kg^-1) ingested the microplastics, but there was no evidence of Zn accumulation, mortality, or weight change. Digestion of the earthworms showed that they did not retain microplastics in their gut. These findings indicate that microplastics could act as vectors to increase metal exposure in earthworms, but that the associated risk is unlikely to be significant for essential metals such as Zn that are well regulated by metabolic processes.

Diverse impacts of a step and repeated BDE209-Pb exposures on accumulation and metabolism of BDE209 in earthworms

Decabromodiphenyl ether (BDE209) and lead (Pb) are the two common contaminants at e-waste recycling sites (EWRSs). A laboratory incubation study was conducted to explore the impacts of a step and repeated BDE209-Pb exposures on accumulation and metabolism of BDE209 in earthworms Eisenia fetida for the first time. The results indicated that BDE209 concentrations in repetitively-polluted soils were clearly higher. And the existence of high-level Pb could promote the bioaccumulation of BDE209 in earthworms along the exposure time. The post-clitellum contents of BDE209 were more than the pre-clitellum during the entire incubation. Additionally, GC/MS analysis results demonstrated that BDE206, BDE208, BDE153, BDE99, BDE47 and BDE28 could be detected in Eisenia fetida throughout 28-d experiment, and BDE206 and BDE208 were predominant metabolic products. A step exposure decreased the capability to metabolize BDE209 in the presence of Pb. Average bioaccumulation factor (BAF) for a step treatment was 0.525, as well as it was more than 1.1 times that of repeated exposure (BAF = 0.48). SEM observations suggested that a step exposure mode aggravated the damage in earthworms than repeated exposure. The results and related findings will establish a useful scientific basis for soil ecological risk assessment at EWRSs.

Bioaccumulation of polycyclic aromatic hydrocarbons and survival of earthworms (Eisenia andrei) exposed to biochar amended soils

Biochar has a charcoal polycyclic aromatic structure which allows its long half-life in soil, making it an ideal tool for C sequestration and for adsorption of organic pollutants, but at the same time raises concerns about possible adverse impacts on soil biota. Two biochars were tested under laboratory-controlled conditions on Eisenia andrei earthworms: a biochar produced at low temperature from wine tree cuttings (WTB) and a commercial low tar hardwood lump charcoal (HLB). The avoidance test (48-h exposure) showed that earthworms avoid biochar-treated soil with rates higher than 16 t ha(-1) for HLB and 64 t ha(-1) for WTB. After 42 days, toxic effects on earthworms were observed even at application rates (100 t ha(-1)) that are generally considered beneficial for most crops. The concentration of HLB and WTB required to kill half of earthworms' population (LC50; 95% confidence limits) in the synthetic OECD soil was 338 and 580 t ha(-1), respectively. Accumulation of polycyclic aromatic hydrocarbons (PAH) in earthworms exposed to the two biochar types at 100 t ha(-1) was tested in two soils of different texture. In biochar-treated soils, the average earthworm survival rates were about 64% in the sandy and 78% clay-loam soils. PAH accumulation was larger in the sandy soil and largest in soils amended with HLB. PAH with less than four rings were preferentially scavenged from the soil by biochars, and this behaviour may mask that of the more dangerous components (i.e. four to five rings), which are preferentially accumulated. Earthworms can accumulate PAH as a consequence of exposure to biochar-treated soils and transfer them along the food chain. Soil type and biochar quality are both relevant in determining PAH transfer.

Earthworm Uptake Routes and Rates of Ionic Zn and ZnO Nanoparticles at Realistic Concentrations, Traced Using Stable Isotope Labeling

The environmental behavior of ZnO nanoparticles (NPs), their availability to, uptake pathways by, and biokinetics in the earthworm Lumbricus rubellus were investigated using stable isotope labeling. Zinc isotopically enriched to 99.5% in (68)Zn ((68)Zn-E) was used to prepare (68)ZnO NPs and a dissolved phase of (68)Zn for comparison. These materials enabled tracing of environmentally relevant (below background) NP additions to soil of only 5 mg (68)Zn-E kg(-1). Uptake routes were isolated by introducing earthworms with sealed and unsealed mouthparts into test soils for up to 72 h. The Zn isotope compositions of the soils, pore waters and earthworms were then determined using multiple collector inductively coupled plasma mass spectrometry. Detection and quantification of (68)Zn-E in earthworm tissue was possible after only 4 h of dermal exposure, when the uptake of (68)Zn-E had increased the total Zn tissue concentration by 0.03‰. The results demonstrate that at these realistic exposure concentrations there is no distinguishable difference between the uptake of the two forms of Zn by the earthworm L. rubellus, with the dietary pathway accounting for ∼95% of total uptake. This stands in contrast to comparable studies where high dosing levels were used and dermal uptake is dominant.

Thresholds of arsenic toxicity to Eisenia fetida in field-collected agricultural soils exposed to copper mining activities in Chile

Several previous studies highlighted the importance of using field-collected soils-and not artificially-contaminated soils-for ecotoxicity tests. However, the use of field-collected soils presents several difficulties for interpretation of results, due to the presence of various contaminants and unavoidable differences in the physicochemical properties of the tested soils. The objective of this study was to estimate thresholds of metal toxicity in topsoils of 24 agricultural areas historically contaminated by mining activities in Chile. We performed standardized earthworm reproduction tests (OECD 222 and ISO 11268-2) with Eisenia fetida. Total soil concentrations of Cu, As, Zn, and Pb were in the ranges of 82-1295 mg kg(-1), 7-41 mg kg(-1), 86-345 mg kg(-1), and 25-97 mg kg(-1), respectively. In order to differentiate between the effects of different metals, we used regression analysis between soil metal concentrations and earthworm responses, as well as between metal concentrations in earthworm tissues and earthworm responses. Based on regression analysis, we concluded that As was a metal of prime concern for Eisenia fetida in soils affected by Cu mining activities, while Cu exhibited a secondary effect. In contrast, the effects of Zn and Pb were not significant. Soil electrical conductivity was another significant contributor to reproduction toxicity in the studied soils, forcing its integration in the interpretation of the results. By using soils with electrical conductivity ≤ 0.29 dS m(-1) (which corresponds to EC50 of salt toxicity to Eisenia fetida), it was possible to isolate the effect of soil salinity on earthworm reproduction. Despite the confounding effects of Cu, it was possible to determine EC10, EC25 and EC50 values for total soil As at 8 mg kg(-1), 14 mg kg(-1) and 22 mg kg(-1), respectively, for the response of the cocoon production. However, it was not possible to determine these threshold values for juvenile production. Likewise, we were able to determine EC10, EC25 and EC50 of earthworm tissue As of 38 mg kg(-1), 47 mg kg(-1), and 57 mg kg(-1), respectively, for the response of the cocoon production. Finally, we determined the no-observed effect concentration of tissue As in E. fetida of 24 mg kg(-1). Thus, earthworm reproduction test is applicable for assessment of metal toxicity in field-collected soils with low electrical conductivity, while it might have a limited applicability in soils with high electrical conductivity because the salinity-induced toxicity will hinder the interpretation of the results.

Influence of soil properties on the bioaccumulation and effects of arsenic in the earthworm Eisenia andrei

This study aimed at assessing the influence of soil properties on the uptake and toxicity effects of arsenic in the earthworm Eisenia andrei exposed for 4 weeks to seven natural soils spiked with different arsenic concentrations. Water-soluble soil concentrations (AsW) and internal As concentrations in the earthworms (AsE) were greatly different between soils. These two variables were highly correlated and were key factors in earthworm toxicity response. AsW was explained by some soil properties, such as the pH, calcium carbonate content, ionic strength, texture or oxide forms. Toxicity showed a clear variation between soils, in some cases without achieving 50 % adverse effect at the highest As concentration added (600 mg kg(-1)). Nevertheless, soil properties did not show, in general, a high relation with studied toxicity endpoints, although the high correlation with AsW could greatly reduce indirectly As bioavailability and toxicity risk for earthworms. Obtained results suggest that soil properties should be part of the criteria to establishing thresholds for contaminated soils because they will be key in controlling As availability and thus result in different degrees of toxicity.

Short-term soil bioassays may not reveal the full toxicity potential for nanomaterials; bioavailability and toxicity of silver ions (AgNO₃) and silver nanoparticles to earthworm Eisenia fetida in long-term aged soils

This study investigated if standard risk assessment hazard tests are long enough to adequately provide the worst case exposure for nanomaterials. This study therefore determined the comparative effects of the aging on the bioavailability and toxicity to earthworms of soils dosed with silver ions and silver nanoparticles (Ag NP) for 1, 9, 30 & 52 weeks, and related this to the total Ag in the soil, Ag in soil pore water and earthworm tissue Ag concentrations. For ionic Ag, a classical pattern of reduced bioavailability and toxicity with time aged in the soil was observed. For the Ag NP, toxicity increased with time apparently driven by Ag ion dissolution from the added Ag NPs. Internal Ag in the earthworms did not always explain toxicity and suggested the presence of an internalised, low-toxicity Ag fraction (as intact or transformed NPs) after shorter aging times. Our results indicate that short-term exposures, without long-term soil aging, are not able to properly assess the environmental risk of Ag NPs and that ultimately, with aging time, Ag ion and Ag NP effect will merge to a common value.

Toxicokinetics of metals in the earthworm Lumbricus rubellus exposed to natural polluted soils--relevance of laboratory tests to the field situation

The aim of this study was to estimate the bioavailability of essential (Zn, Cu) and non-essential metals (Cd, Pb) to the earthworm Lumbricus rubellus exposed to soils originating from a gradient of metal pollution in Southern Poland. Metal uptake and elimination kinetics were determined and related to soils properties. Experimental results were compared with tissue metal concentrations observed in earthworms from the studied transect. Cd and Pb were intensively accumulated by the earthworms, with very slow or no elimination. Their uptake rate constants, based on 0.01 M CaCl2-extractable concentrations in the soils, increased with soil pH. Internal concentrations of Cu and Zn were maintained by the earthworms at a stable level, suggesting efficient regulation of these metals by the animals. The estimated uptake and elimination kinetics parameters enabled fairly accurate prediction of metal concentrations reached within a life span of L. rubellus in nature.

Determining the bioavailability and toxicity of lead contamination to earthworms requires using a combination of physicochemical and biological methods

This study aimed at assessing the bioavailability and toxicity of lead to Eisenia andrei in shooting range soils representing different land uses (forest, grassland, bullet plot). Soils contained 47-2398 mg Pb/kg dry weight (dw), but also had different pH-CaCl2 (3.2-6.8) and organic matter contents (3.8-13%). Therefore artificial soils with different pH and organic matter contents and two natural soils were included as control soils. Earthworms were exposed for 28 days and toxicity and uptake of Pb were related to total, water and 0.01 M CaCl2 extractable and porewater Pb concentrations as well as to soil characteristics. Pb uptake in the earthworms linearly increased with increasing soil concentrations. At >2000 mg Pb/kg dw and pH 3.3-3.5, high earthworm mortality with significant weight loss and complete inhibition of reproduction were recorded. At <1000 mg/kg dw, earthworm reproduction was more related to differences in pH and other soil characteristics than to Pb.

Ecotoxicological study of arsenic and lead contaminated soils in former orchards at the Hanford Site, USA

The purpose of this study was to assess ecotoxicity of former orchard soils contaminated with lead arsenate pesticides at the Hanford Site in Washington state (USA). Surface soil, plant, and invertebrate samples were collected from 11 sites in former orchard areas. Mean (standard deviation [SD]) for As and Pb in soil were 39.5 (40.6) and 208 (142) mg/kg dry wt, respectively (n = 11). These concentrations exceeded Hanford background levels but were similar to orchard soils elsewhere. In our study, As and Pb soil concentrations were positively and significantly correlated (r = 0.87, Bonferroni P < 0.05). Speciation of total inorganic As in soil (n = 6) demonstrated that As+5 was the dominant form (>99%). Mean (SD) for As and Pb in cheatgrass were 3.9 (7.9) and 12.4 (20.0) mg/kg dry wt, respectively (n = 11), while mean (SD) for As and Pb in darkling beetles were 5.4 (2.6) and 3.9 (3.0) mg/kg dry wt, respectively (n = 8). Linear regressions were constructed to estimate soil to cheatgrass and soil to darkling beetle uptake for As and Pb. These were significant (Bonferroni P < 0.05) only for cheatgrass versus soil (As) and darkling beetle versus soil (Pb). Standardized lettuce seedling and earthworm bioassays were performed with a subset of soil samples (n = 6). No significant effects (P > 0.05) were observed in lettuce survival or growth nor in earthworm survival or sublethal effects. Based on these bioassays, unbounded no observed effect concentrations (NOECs) in soil for As and Pb were 128 and 390 mg/kg dry wt, respectively. However, our range of soil concentrations generally overlapped a set of ecotoxicological benchmarks reported in the literature. Given uncertainty and limited sampling related to our NOECs, as well as uncertainty in generic benchmarks from the literature, further study is needed to refine characterization of As and Pb ecotoxicity in former orchard soils at the Hanford Site.

Pseudo-basal levels of and distribution of anti-oxidant enzyme biomarkers in Eisenia fetida and effect of exposure to phenanthrene

In the paper, the pseudo-basal levels of anti-oxidant system in different earthworm life stages (juvenile and adult) and the pseudo-basal distribution in different regions of adult earthworms (pre-clitellum, clitellum and post-clitellum) were studied using filter contact tests. The effects of phenanthrene (PHE) at different exposure levels on anti-oxidant enzymes along the earthworm body were also investigated after 24 and 48h of exposure. The pseudo-basal levels of the anti-oxidant enzymes varied during the different growth phase, and results indicated that earthworm has a low oxidative risk and SOD plays important roles during the development whereas CAT and POD are more important in maintain the low ROS level in adult earthworm. The pseudo-basal distribution of the anti-oxidant enzymes along the earthworms was heterogeneous and MDA mainly located in clitellum. POD in pre-clitellum, SOD in clitellum and CAT in post-clitellum were important to eliminate excess total ROS. Time of exposure impacted the anti-oxidant enzyme activities and their distribution patterns along earthworms, from the viewpoint of which supported that exposure time was an environment stress factors. In a short exposure time (24 h), CAT and SOD in the three regions, POD in pre-clitellum and clitellum might be good indicator to a low PHE stress level (0.0629 μg cm(-2) treatments). In a long exposure time (48 h), only SOD in clitellum is a good indicator to both low and high PHE stress (0.629 μg cm(-2) treatments). Earthworm biomembrane system inflicted no oxidative damage until the stress magnitude reached or exceeds the level of exposure in low PHE concentration condition for 48 h.

Passive samplers provide a better prediction of PAH bioaccumulation in earthworms and plant roots than exhaustive, mild solvent, and cyclodextrin extractions

A number of extraction methods have been developed to assess polycyclic aromatic hydrocarbon (PAH) bioavailability in soils. As these methods are rarely tested in a comparative manner, against different test organisms, and using field-contaminated soils, it is unclear which method gives the most accurate measure of the actual soil ecosystem exposure. In this study, PAH bioavailability was assessed in ten field-contaminated soils by using exhaustive acetone/hexane extractions, mild solvent (butanol) extractions, cyclodextrin extractions, and two passive sampling methods; solid phase micro extraction (SPME) and polyoxymethylene solid phase extraction (POM-SPE). Results were compared to actual PAH bioaccumulation in earthworms (Eisenia fetida) and rye grass (Lolium multiflorum) roots. Exhaustive, mild solvent and cyclodextrin extractions consistently overpredicted biotic concentrations by a factor of 10-10 000 and therefore seem inappropriate for predicting PAH bioaccumulation in field contaminated soils. In contrast, passive samplers generally predicted PAH concentrations in earthworms within a factor of 10, although correlations between predicted and measured concentrations were considerably scattered. The same applied to the plant data, where passive samplers also tended to underpredict root concentrations. These results indicate the potential of passive samplers to predict PAH bioaccumulation, yet call for comparative studies between passive samplers and further research on plant bioavailability.

Impact of gut passage and mucus secretion by the earthworm Lumbricus terrestris on mobility and speciation of arsenic in contaminated soil

Earthworms inhabiting arsenic contaminated soils may accelerate the leaching of As into surface and ground waters. We carried out three experiments to determine the impact of passage of As contaminated soil (1150 mg As kg(-1)) through the gut of the earthworm Lumbricus terrestris on the mobility and speciation of As and the effects of earthworm mucus on As mobility. The concentration of water soluble As in soil increased (from 1.6 to 18 mg kg(-1)) after passage through the earthworm gut. Casts that were aged for 56 days still contained more than nine times greater water soluble As than bulk earthworm inhabited soil. Changes were due to increases in As(V) mobility, with no change in As(III). Dilute mucus extracts reduced As mobility through the formation of As-amino acid-iron oxide ternary complexes. More concentrated mucus extracts increased As mobility. These changes, together with those due to the passage through the gut, were due to increases in pH, phosphate and soluble organic carbon. The mobilisation of As from contaminated soils in the environment by cast production and mucus secretion may allow for accelerated leaching or uptake into biota which is underestimated when bulk soil samples are analysed and the influence of soil biota ignored.

Arsenic speciation in field-collected and laboratory-exposed earthworms Lumbricus terrestris

Mature Lumbricus terrestris were host soils and leaf litter were collected from a former arsenic mine in Devon, UK (Devon Great Consols), a former gold mine in Ontario, Canada (Deloro), and an uncontaminated residential garden in Nottingham, UK. Arsenic concentrations determined by inductively coupled plasma-mass spectrometry (ICP-MS) in soils were 16-348 mg kg(-1), 6.0-239 mg kg(-1) in the earthworms and 8.6 mg kg(-1) in leaf litter sampled at Deloro (all dry weight). High performance liquid chromatography (HPLC-ICP-MS) analysis revealed arsenite (As(III)), arsenate (As(V)) and five organoarsenic species; arsenobetaine (AB), methylarsonate (MA(V)), dimethylarsinate (DMA(V)), arsenosugar 1 (glycerol sugar), arsenosugar 2 (phosphate sugar), and trimethylarsineoxide (TMAO) in field-collected L. terrestris. Differences were observed in the variety of organoarsenic species present between field sites. Several organoarsenic species were observed in the leaf litter (DMA(V), arsenosugar 2 and TMAO) but not AB. Depuration resulted in higher concentrations of inorganic As being detected in the earthworm whereas the concentration or variety of organoarsenic species was unchanged. Commercially sourced L. terrestris were exposed to As contaminated soil in laboratory mesocosms (1.0, 98, 183, 236, 324 and 436 mg kg(-1)) without leaf litter and were additionally analyzed using X-ray absorption near edge structure (XANES). Only inorganic As(III) and As(V) was observed. It is proposed that ingestion of leaf litter and symbiotic processes in the natural soil environment are likely sources of organoarsenic compounds in field-collected L. terrestris.

Bioavailability pathways underlying zinc-induced avoidance behavior and reproduction toxicity in Lumbricus rubellus earthworms

We investigated possible bioavailability pathways underlying zinc-induced avoidance behavior and sublethal reproduction impairment in Lumbricus rubellus. Clay-loam (pH 7.3) and sandy soil (three pH values of 4.3-6.0) were amended with zinc sulfate at six soil concentrations of total Zn ranging from 0.1 to 36 mmol/kg dw. Estimated and measured concentrations of free and exchangeable Zn ranged 10(-4) to 7.1 mmol/l. Avoidance behavior responses were fast and could be directly predicted from the activity of free zinc ions without a modifying pH effect. The repellent effect is thus likely mediated by a direct action of Zn(2+) ions on epidermal chemosensitive receptors. Body zinc uptake, however, was determined by proton competition with free Zn(2+) sorption. Excess accumulation of body Zn was a good predictor of reproduction decline, which is indicative of internal zinc poisoning. The results indicated that zinc affects earthworms via both direct and indirect mechanisms of external and internal exposure.

Impact of earthworms on trace element solubility in contaminated mine soils amended with green waste compost

The common practice of remediating metal contaminated mine soils with compost can reduce metal mobility and promote revegetation, but the effect of introduced or colonising earthworms on metal solubility is largely unknown. We amended soils from an As/Cu (1150 mg As kg(-1) and 362 mg Cu kg(-1)) and Pb/Zn mine (4550 mg Pb kg(-1) and 908 mg Zn kg(-1)) with 0, 5, 10, 15 and 20% compost and then introduced Lumbricus terrestris. Porewater was sampled and soil extracted with water to determine trace element solubility, pH and soluble organic carbon. Compost reduced Cu, Pb and Zn, but increased As solubility. Earthworms decreased water soluble Cu and As but increased Pb and Zn in porewater. The effect of the earthworms decreased with increasing compost amendment. The impact of the compost and the earthworms on metal solubility is explained by their effect on pH and soluble organic carbon and the environmental chemistry of each element.

Suitability of lysosomal membrane stability in Eisenia fetida as biomarker of soil copper contamination

Accumulated metals in soils negatively affect dwelling organisms. Earthworms, which are widespread and perform various essential functions, are able to accumulate metals that can damage the coelomic cells. The aim of this work was to evaluate the effect on Eisenia fetida lysosomal membrane stability both during and after copper exposure, and finally to link this to internal concentrations. E. fetida specimens were exposed to a reference soil and two Cu-spiked soils (35 and 350 mg kg(-1) d.w.) for 14 days (uptake period) and then transferred into the reference soil for other 18 days (elimination period). After 3 days of uptake, internal Cu concentrations increased and were higher in the specimens exposed to soils spiked with 350 mg Cu kg(-1) d.w. After 2 days of elimination, a strong decrease of internal Cu concentrations was always observed. The lysosomal membrane stability, measured as neutral red retention-times, was approximately 50 min for the earthworms exposed to the reference soils, whereas it decreased, at the end of the uptake period, to 21 and 13 min, respectively, for the organisms exposed to soils spiked with 35 and 350 mg Cu kg(-1) d.w. A full recovery of the lysosomal membrane stability was reached after 14 and 18 days of the elimination period, respectively, for the organisms exposed to soils spiked with 35 and 350 mg Cu kg(-1) d.w. The neutral-red assay would seem a good biomarker since the lysosomal membrane stability of E. fetida appeared to respond rapidly and strongly to soil copper contamination.

The bioaccumulation of Molybdenum in the earthworm Eisenia andrei: influence of soil properties and ageing

Mo bioaccumulation in the earthworm Eisenia andrei was determined after 28 d exposure in ten different European field soils (pH 4.4-7.8) and an artificial soil, freshly spiked with Na₂MoO₄ at concentrations between 3.2 and 3200 mg Mo kg⁻¹ dry soil. Three field soils were also tested after ageing for 11 months. Earthworm Mo concentrations generally levelled off at high exposure levels but in most soils showed a (nearly) linear increase with increasing soil concentrations in the lower, non-toxic range (below EC10 or NOEC for reproduction effects). Bioaccumulation (BAF) and Bioconcentration factors (BCF) were calculated as the ratio of earthworm concentration to soil and estimated porewater concentrations, respectively. BAFs (0.35-3.44) and BCFs (1.31-276) did not seem much affected by soil concentration, suggesting that earthworms are not capable of regulating their internal Mo concentrations. BAF was best predicted by ammonium oxalate-extractable iron (Fe(ox)) and phosphor (P(ox)) contents of the soils.

Impact of the earthworm Lumbricus terrestris (L.) on As, Cu, Pb and Zn mobility and speciation in contaminated soils

To assess the risks that contaminated soils pose to the environment properly a greater understanding of how soil biota influence the mobility of metal(loid)s in soils is required. Lumbricus terrestris L. were incubated in three soils contaminated with As, Cu, Pb and Zn. The concentration and speciation of metal(loid)s in pore waters and the mobility and partitioning in casts were compared with earthworm-free soil. Generally the concentrations of water extractable metal(loid)s in earthworm casts were greater than in earthworm-free soil. The impact of the earthworms on concentration and speciation in pore waters was soil and metal specific and could be explained either by earthworm induced changes in soil pH or soluble organic carbon. The mobilisation of metal(loid)s in the environment by earthworm activity may allow for leaching or uptake into biota.

Genotoxic endpoints in the earthworms sub-lethal assay to evaluate natural soils contaminated by metals and radionuclides

Eisenia andrei was exposed, for 56 days, to a contaminated soil from an abandoned uranium mine and to the natural reference soil LUFA 2.2. The organisms were sampled after 0, 1, 2, 7, 14 and 56 days of exposure, to assess metals bioaccumulation, coelomocytes DNA integrity and cytotoxicity. Radionuclides bioaccumulation and growth were also determined at 0 h, 14 and 56 days of exposure. Results have shown the bioaccumulation of metals and radionuclides, as well as, growth reduction, DNA damages and cytotoxicity in earthworms exposed to contaminated soil. The usefulness of the comet assay and flow cytometry, to evaluate the toxicity of contaminants such as metals and radionuclides in earthworms are herein reported. We also demonstrated that DNA strand breakage and immune cells frequency are important endpoints to be employed in the earthworm reproduction assay, for the evaluation of soil geno and cytotoxicity, as part of the risk assessment of contaminated areas. This is the first study that integrates DNA damage and cytotoxicity evaluation, growth and bioaccumulation of metals and radionuclides in a sub lethal assay, for earthworms exposed to soil contaminated with metals and radionuclides.

Effects of biochar and the earthworm Eisenia fetida on the bioavailability of polycyclic aromatic hydrocarbons and potentially toxic elements

Polycyclic aromatic hydrocarbons (PAHs) and potentially toxic elements (PTEs) were monitored over 56 days in calcareous contaminated-soil amended with either or both biochar and Eisenia fetida. Biochar reduced total (449 to 306 mg kg(-1)) and bioavailable (cyclodextrin extractable) (276 to 182 mg kg(-1)) PAHs, PAH concentrations in E. fetida (up to 45%) but also earthworm weight. Earthworms increased PAH bioavailability by >40%. Combined treatment results were similar to the biochar-only treatment. Earthworms increased water soluble Co (3.4 to 29.2 mg kg(-1)), Cu (60.0 to 120.1 mg kg(-1)) and Ni (31.7 to 83.0 mg kg(-1)) but not As, Cd, Pb or Zn; biochar reduced water soluble Cu (60 to 37 mg kg(-1)). Combined treatment results were similar to the biochar-only treatment but gave a greater reduction in As and Cd mobility. Biochar has contaminated land remediation potential, but its long-term impact on contaminants and soil biota needs to be assessed.

Molecular genetic differentiation in earthworms inhabiting a heterogeneous Pb-polluted landscape

A Pb-mine site situated on acidic soil, but comprising of Ca-enriched islands around derelict buildings was used to study the spatial pattern of genetic diversity in Lumbricus rubellus. Two distinct genetic lineages ('A' and 'B'), differentiated at both the mitochondrial (mtDNA COII) and nuclear level (AFLPs) were revealed with a mean inter-lineage mtDNA sequence divergence of approximately 13%, indicative of a cryptic species complex. AFLP analysis indicates that lineage A individuals within one central 'ecological island' site are uniquely clustered, with little genetic overlap with lineage A individuals at the two peripheral sites. FTIR microspectroscopy of Pb-sequestering chloragocytes revealed different phosphate profiles in residents of adjacent acidic and calcareous islands. Bioinformatics found over-representation of Ca pathway genes in EST(Pb) libraries. Subsequent sequencing of a Ca-transport gene, SERCA, revealed mutations in the protein's cytosolic domain. We recommend the mandatory genotyping of all individuals prior to field-based ecotoxicological assays, particularly those using discriminating genomic technologies.

Influence of clay content on bioavailability of copper in the earthworm Eisenia fetida

We investigated the effect of clay content on the bioavailability of copper to the earthworm Eisenia fetida, in the laboratory for 28 days using OECD artificial soil adjusted to 5%, 20% and 40% clay. Mortality, growth, cocoon production and internal copper concentrations were assessed in worms, and total, DTPA and CaCl(2) extractable copper in the substrates were also determined. The results showed that with increased clay content, there was significant reduction in internal Cu concentration of worms as well as toxicity of copper as shown by data for growth and mortality. However, internal copper concentrations of worms could not explain fully the observed toxicity in this study probably because of Cu regulation. Among the three extraction methods, DTPA extraction revealed the strongest relationship between partitioning and toxicity of Cu in this study. DTPA extract is thus a promising surrogate measure of bioavailability of Cu to earthworms. It is concluded that clay content has significant influence on the bioavailability of copper to earthworms and other similar species.

Uptake kinetics of metals by the earthworm Eisenia fetida exposed to field-contaminated soils

It is well known that earthworms can accumulate metals. However, most accumulation studies focus on Cd-, Cu-, Pb- or Zn-amended soils, additionally few studies consider accumulation kinetics. Here we model the accumulation kinetics of 18 elements by Eisenia fetida, exposed to 8 metal-contaminated and 2 uncontaminated soils. Tissue metal concentration was determined after 3, 7, 14, 21, 28 and 42 days. Metal elimination rate was important in determining time to reach steady-state tissue metal concentration. Uptake flux to elimination rate ratios showed less variation and lower values for essential than for non-essential metals. In theory kinetic rate constants are dependent only on species and metal. Therefore it should be possible to predict steady-state tissue metal concentrations on the basis of very few measurements using the rate constants. However, our experiments show that it is difficult to extrapolate the accumulation kinetic constants derived using one soil to another.

Accumulated metal speciation in earthworm populations with multigenerational exposure to metalliferous soils: cell fractionation and high-energy synchrotron analyses

Predicting metal bioaccumulation and toxicity in soil organisms is complicated by site-specific biotic and abiotic parameters. In this study we exploited tissue fractionation and digestion techniques, combined with X-ray absorption spectroscopy (XAS), to investigate the whole-body and subcellular distributions, ligand affinities, and coordination chemistry of accumulated Pb and Zn in field populations of the epigeic earthworm Lumbricus rubellus inhabiting three contrasting metalliferous and two unpolluted soils. Our main findings were (i) earthworms were resident in soils with concentrations of Pb and Zn ranging from 1200 to 27,000 mg kg(-1) and 200 to 34,000 mg kg(-1), respectively; (ii) Pb and Zn primarily accumulated in the posterior alimentary canal in nonsoluble subcellular fractions of earthworms; (iii) site-specific differences in the tissue and subcellular partitioning profiles of populations were observed, with earthworms from a calcareous site partitioning proportionally more Pb to their anterior body segments and Zn to the chloragosome-rich subcellular fraction than their acidic-soil inhabiting counterparts; (iv) XAS indicated that the interpopulation differences in metal partitioning between organs were not accompanied by qualitative differences in ligand-binding speciation, because crystalline phosphate-containing pyromorphite was a predominant chemical species in the whole-worm tissues of all mine soil residents. Differences in metal (Pb, Zn) partitioning at both organ and cellular levels displayed by field populations with protracted histories of metal exposures may reflect theirinnate ecophysiological responses to essential edaphic variables, such as Ca2+ status. These observations are highly significant in the challenging exercise of interpreting holistic biomarker data delivered by "omic" technologies.

Concentration of Cd, Cu, Pb, Zn, Al, and Fe in soils of Manresa, NE Spain

The aims of this study were to determine the contents of cadmium (Cd), copper (Cu), lead (Pb), zinc (Zn), aluminium (Al), and iron (Fe) (aqua regia-extractable) in 27 soil plots (54 samples) from Manresa, NE Spain, and to establish relationships between heavy metals and some soil properties. The main soil types were surveyed and the median concentrations (mg kg(-1)) obtained were Cd 0.28, Cu 20.3, Pb 18.6, Zn 67.4, Al 22,572, and Fe 21,551. Element concentrations for these soils were lower than the published values for the Valencia region (Spain) and Torrelles and Sant Climent municipal districts (Catalonia, Spain). In terms of soil properties, the results of this study suggest that, in Manresa soils, both trace element adsorption and retention are influenced by several properties such as clay minerals, carbonates, organic matter, and pH. All element contents were positively correlated with clay content. Pb and Zn were negatively correlated with pH and CaCO(3).

A Cu tolerant population of the earthworm Dendrodrilus rubidus (Savigny, 1862) at Coniston Copper Mines, Cumbria, UK

Dendrodrilus rubidus were sampled from a mine spoil soil at Coniston Copper Mine, an abandoned Cu mine in Cumbria, UK and a Cu-free control site. Earthworms were maintained for 14d in both Kettering loam and a Moorland soil amended with Cu nitrate. Mortality, condition index, weight change and tissue concentration were determined. In both soils D. rubidus native to the mine site were able to tolerate significantly higher soil Cu concentrations (MWRT, p<or=0.001), and exhibited significantly less change in weight (t-test, p<or=0.001) and a lower loss in condition (t-test, p<or=0.001) than control earthworms. For a given soil Cu concentration tissue Cu concentrations were greater in the mine site earthworms. Low cocoon production and viability from the mine site population prevented the determination of toxicity parameters on the F1 generation and may be an indicator of the cost of tolerance to the population.