Assessing ecotoxicity and uptake of metals and metalloids in relation to two different earthworm species (Eiseina hortensis and Lumbricus terrestris)

Toxicokinetics of selenate in earthworm sub-tissues and potential bio-accessibility assessment of earthworm-derived selenium

Selenium (Se) pollution is mainly caused by anthropogenic activities, and the resulting biosecurity concerns have garnered significant attention in recent years. Using one-compartmental toxicokinetic (TK) modelling, this study explored the kinetic absorption, sub-tissue distribution, and elimination processes of the main Se species (selenate, Se(VI)) in the cultivated aerobic soil of the earthworm Eisenia fetida. The bio-accessibility of earthworm-derived Se was assessed using an in vitro simulated gastrointestinal digestion test to evaluate its potential trophic risk. The results demonstrated that Se accumulated in the pre-clitellum (PC) and total tissues (TT) of earthworms in a time- and dose-dependent manner. The highest Se levels in the PC, post-clitellum (PoC), and TT were 70.54, 57.93, and 64.26 mg/kg during the uptake phase, respectively. The kinetic Se contents in the earthworms PC and TT were consistent with the TK model but not with PoC. The earthworm TT exhibited a faster uptake (Kus = 0.83-1.02 mg/kg/day) and elimination rate of Se (Kee = 0.044-0.049 mg/kg/day), as well as a shorter half-life time (LT1/2 = 15.88-14.22 days) than PC at low soil Se levels (≤5 mg/kg). Conversely, the opposite trend was observed with higher Se concentrations (10 and 20 mg/kg). These results are likely attributable to the tissue specificity and concentration of the toxicant. Earthworms PC and TT exhibited a higher kinetic Se accumulation factor (BAFk) than steady-state BAF (BAFss), with values ranging from 8 to 24 and 3-13, respectively. Furthermore, the bio-accessibility of earthworm-derived Se to poultry ranged from 66.25 % to 84.35 %. As earthworms are at the bottom of the terrestrial food chain, the high bio-accessibility of earthworm-derived Se poses a potential risk to predators. This study offers data support and a theoretical foundation for understanding the biological footprint of soil Se and its toxicological impacts and ecological hazards.

Combined effects of cadmium and sulfamethoxazole on Eisenia fetida: Insights into accumulation, subcellular partitioning, biomarkers and toxicological responses

Cadmium (Cd) and sulfamethoxazole (SMX) frequently coexist in farmlands, yet their synergistic toxicological impacts on terrestrial invertebrates remain unexplored. In this study, earthworms were exposed to artificial soils percolated with Cd (5 mg/kg), SMX (5 mg/kg) or combination of them for 7 days, followed by a 12-day elimination phase in uncontaminated soil. The uptake of Cd and SMX by the earthworms, along with their subcellular distribution, was meticulously analyzed. Additionally, a suite of biomarkers-including superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), and weight loss-were evaluated to assess the health status of the earthworms and the toxicological effects of the Cd and SMX mixture. Notably, the cotreatment with Cd and SMX resulted in a significantly higher weight loss in Eisenia fetida (41.25 %) compared to exposure to Cd alone (26.84 %). Moreover, the cotreatment group exhibited substantially higher concentrations of Cd in the total internal body, fraction C (cytosol), and fraction E (tissue fragments and cell membranes) in Eisenia fetida compared to Cd alone counterparts. The combined exposure also significantly elevated the SMX levels in the total body and fraction C compared with the SMX-only treated earthworms. Additionally, Eisenia fetida subjected to the combined treatment showed markedly increased activities of SOD, CAT, and MDA compared to those treated with Cd alone. The effect addition indices (EAIs), ranging from 1.00 to 2.23, unequivocally demonstrated a synergistic effect of the combined treatments. Interestingly, relocating the earthworms to clean soil did not mitigate the observed adverse effects. These findings underscore the increased risk posed by the Cd-SMX complex to terrestrial invertebrates in agricultural areas.

Assessment of growth, reproduction, and vermi-remediation potentials of Eisenia fetida on heavy metal exposure

Heavy metal pollution is a significant environmental concern with detrimental effects on ecosystems and human health, and traditional remediation methods may be costly, energy-intensive, or have limited effectiveness. The current study aims were to investigate the impact of heavy metal toxicity in Eisenia fetida, the growth, reproductive outcomes, and their role in soil remediation. Various concentrations (ranging from 0 to 640 mg per kg of soil) of each heavy metal were incorporated into artificially prepared soil, and vermi-remediation was conducted over a period of 60 days. The study examined the effects of heavy metals on the growth and reproductive capabilities of E. fetida, as well as their impact on the organism through techniques such as FTIR, histology, and comet assay. Atomic absorption spectrometry demonstrated a significant (P < 0.000) reduction in heavy metal concentrations in the soil as a result of E. fetida activity. The order of heavy metal accumulation by E. fetida was found to be Cr > Cd > Pb. Histological analysis revealed a consistent decline in the organism's body condition with increasing concentrations of heavy metals. However, comet assay results indicated that the tested levels of heavy metals did not induce DNA damage in E. fetida. FTIR analysis revealed various functional group peaks, including N-H and O-H groups, CH2 asymmetric stretching, amide I and amide II, C-H bend, carboxylate group, C-H stretch, C-O stretching of sulfoxides, carbohydrates/polysaccharides, disulfide groups, and nitro compounds, with minor shifts indicating the binding or accumulation of heavy metals within E. fetida. Despite heavy metal exposure, no significant detrimental effects were observed, highlighting the potential of E. fetida for sustainable soil remediation. Vermi-remediation with E. fetida represents a novel, sustainable, and cutting-edge technology in environmental cleanup. This study found that E. fetida can serve as a natural and sustainable method for remediating heavy metal-contaminated soils, promising a healthier future for soil.

Accumulation of heavy metals from single and combined olive mill wastewater and pomace in soil and bioaccumulation in tissues of two earthworm species: Endogeic (Aporrectodea trapezoides) and Epigeic (Eisenia fetida)

Soil and earthworms are threatened by anthropogenic contamination resulting from olive mill waste dumping on the soil due to their pollutant properties. While several studies have explored the effects of olive mill waste on soil properties and the accumulation of heavy metals in soil, there is currently a gap in the literature regarding the potential bioaccumulation of heavy metals from olive mill waste in earthworms. In this study, soil with earthworms from two ecological categories (endogeic: Aporrectodea trapezoides and epigeic: Eisenia fetida) was treated with increasing doses of olive mill wastewater (OMWW) and olive mill pomace (OMP), applied individually or combined, in an indoor experiment in plastic containers, under laboratory conditions. The results revealed the presence of significant concentrations of heavy metals in the two types of wastes ranging as follows: Fe˃ Zn˃ Cu˃ Cd˃ Cr for OMWW, and Fe˃ Zn˃ Cu˃ Cr for OMP (with Cd below the detection limit). The study demonstrated distinct effects of OMWW and OMP, both individually and in combination, on soil heavy metal content, ranging as follows: soil OMWW > soil Combination > soil OMP for Cd; soil Combination > soil OMWW > soil OMP for Cr and Fe; and soil Combination > soil OMP > soil OMWW for Cu and Zn. Additionally, our investigation showed that both earthworm species exhibited significant uptake of these metals into their tissues, particularly the endogeic species. Interestingly, the most significant difference between species was in the accumulation of Cu, with the epigeic species accumulating significantly lower amounts.

Toxic effects of lead on plants: integrating multi-omics with bioinformatics to develop Pb-tolerant crops

MAIN CONCLUSION

Lead disrupts plant metabolic homeostasis and key structural elements. Utilizing modern biotechnology tools, it's feasible to develop Pb-tolerant varieties by discovering biological players regulating plant metabolic pathways under stress. Lead (Pb) has been used for a variety of purposes since antiquity despite its toxic nature. After arsenic, lead is the most hazardous heavy metal without any known beneficial role in the biological system. It is a crucial inorganic pollutant that affects plant biochemical and morpho-physiological attributes. Lead toxicity harms plants throughout their life cycle and the extent of damage depends on the concentration and duration of exposure. Higher levels of lead exposure disrupt numerous key metabolic activities of plants including oxygen-evolving complex, organelles integrity, photosystem II connectivity, and electron transport chain. This review summarizes the detrimental effects of lead toxicity on seed germination, crop growth, and yield, oxidative and ultra-structural alterations, as well as nutrient absorption, transport, and assimilation. Further, it discusses the Pb-induced toxic modulation of stomatal conductance, photosynthesis, respiration, metabolic-enzymatic activity, osmolytes accumulation, and antioxidant activity. It is a comprehensive review that reports on omics-based studies along with morpho-physiological and biochemical modifications caused by lead stress. With advances in DNA sequencing technologies, genomics and transcriptomics are gradually becoming popular for studying Pb stress effects in plants. Proteomics and metabolomics are still underrated and there is a scarcity of published data, and this review highlights both their technical and research gaps. Besides, there is also a discussion on how the integration of omics with bioinformatics and the use of the latest biotechnological tools can aid in developing Pb-tolerant crops. The review concludes with core challenges and research directions that need to be addressed soon.

Association between heavy metal uptake and growth and reproduction in the anecic earthworm, Alma nilotica (Grube 1855)

Elevated heavy metal concentrations in soils are a cause for concern as they are hazardous to soil organisms including earthworms which are considered as ecosystem engineers. Current ecotoxicity tests predominantly use temperate earthworm species, and thus there is the need to include a broader genera of native species to improve ecological risk assessment. Alma nilotica, is a tropical anecic earthworm species that survives well under laboratory conditions and has potential for use in ecotoxicology testing but lacks published toxicity data for important pollutants. Growth and reproduction bioassays were carried out with A. nilotica to determine the relationship between the concentrations of Cu, Zn, Pb and Cr in spiked soils and their bioaccumulation and toxic effects. Positive linear relationships were found between soil-metal and internal earthworm-metal concentrations. Cu did not inhibit growth up to 35 days of exposure but became toxic with longer exposure duration. Zn was not regulated by A. nilotica although it is an essential metal that is well regulated by Eisenia sp. commonly used in standard ecotoxicity tests, showing differences in metal regulation by earthworms of different ecological categories. Based on bioaccumulation factors (BAFs), growth inhibition and reproduction effects the metals were ranked in decreasing toxicity as Pb > Cr > Zn > Cu. The mean 20% Internal Effects Concentrations (IEC20s) for reproduction were 1.04, 2.9, 8.3 and 224.2 mg metal kg-1 earthworm for Pb, Cr, Zn and Cu respectively. These data can contribute to the improvement of metal risk assessment particularly in tropical contexts.

Arsenic toxicity to earthworms in soils of historical As mining sites: an assessment based on various endpoints and chemical extractions

Eisenia fetida is an earthworm species often used to assess the toxicity of contaminants in soils. Several studies indicated that its response can be unpredictable because it depends both on total concentrations of contaminants and also on their forms that differ in susceptibility to be released from soil solid phase. The issue is complex because two various uptake routes are concurrently involved, dermal and ingestion in guts, where the bioavailability of contaminants can considerably change. The aim of this study was to analyze the toxicity of arsenic (As) in various strongly contaminated meadow and forest soils, representative for former As mining and processing area, to earthworms E. fetida and its accumulation in their bodies. An attempt was made to find relationships between the response of earthworms and chemical extractability of As. In the bioassay, carried out according to the standard ISO protocol, different endpoints were applied: earthworm survival, fecundity measured by the numbers of juveniles and cocoons, earthworm weight and As accumulation in the bodies. The results proved that E. fetida can tolerate extremely high total As concentrations in soils, such as 8000 mg/kg, however, the individual endpoints were not correlated and showed different patterns. The most sensitive one was the number of juveniles. No particular soil factor was identified that would indicate an exceptionally high As susceptibility to the release from one of soils, however, we have demonstrated that the sum of non-specifically and specifically bound As (i.e. fractions F1 + F2 in sequential extraction according to Wenzel) could be a good chemical indicator of arsenic toxicity to soil invertebrates.

Evaluation of Acute Toxicity and Antioxidant Response of Earthworm Exposed to a Lignin-Modified Crosslinked Hydrogel

Hydrogels are polymers of great importance due to their multiple applications, which have led to an exponential increase in their production. However, once they have fulfilled their function, they become waste and their ecotoxicological effects are unknown. The aim of the present study was to evaluate the acute toxicity and total antioxidant capacity of the earthworm (Eisenia fetida) exposed to a terpolymeric hydrogel (acrylic acid, acrylamide, and 2-acrylamido-2-methyl-1-propane-sulfonic acid) crosslinked with modified kraft lignin. Four different amounts of hydrogel per unit area were evaluated (0.0924, 0.1848, 0.9242, and 1.848 mg hydrogel/cm²) plus a control, and three replicates were performed for each group. Starting from the amount of 0.1848 mg hydrogel/cm², the earthworms showed physiological and behavioral alterations; at higher amounts, 0.9242 and 1.848 mg hydrogel/cm², more acute signs were observed with mortality rates of 51.7% and 100%, respectively. On the other hand, the antioxidant activity assay showed that the higher the hydrogel exposure amount, the higher the oxidative stress, as evidenced by lower antioxidant activity (67.09% inhibition of the ABTS^●+ radical). Therefore, we concluded that the lignin-modified hydrogel generated oxidative stress and acute lethal toxic effects in Eisenia fetida.

Fungal assisted bio-treatment of environmental pollutants with comprehensive emphasis on noxious heavy metals: Recent updates

In the present time of speedy developments and industrialization, heavy metals are being uncovered in aquatic environment and soil via refining, electroplating, processing, mining, metallurgical activities, dyeing and other several metallic and metal based industrial and synthetic activities. Heavy metals like lead (Pb), mercury (Hg), cadmium (Cd), arsenic (As), Zinc (Zn), Cobalt (Co), Iron (Fe), and many other are considered as seriously noxious and toxic for the aquatic environment, human, and other aquatic lives and have damaging influences. Such heavy metals, which are very tough to be degraded, can be managed by reducing their potential through various processes like removal, precipitation, oxidation-reduction, bio-sorption, recovery, bioaccumulation, bio-mineralization etc. Microbes are known as talented bio-agents for the heavy metals detoxification process and fungi are one of the cherished bio-sources that show noteworthy aptitude of heavy metal sorption and metal tolerance. Thus, the main objective of the authors was to come with a comprehensive review having methodological insights on the novel and recent results in the field of mycoremediation of heavy metals. This review significantly assesses the potential talent of fungi in heavy metal detoxification and thus, in environmental restoration. Many reported works, methodologies and mechanistic sights have been evaluated to explore the fungal-assisted heavy metal remediation. Herein, a compact and effectual discussion on the recent mycoremediation studies of organic pollutants like dyes, petroleum, pesticides, insecticides, herbicides, and pharmaceutical wastes have also been presented.

Ecotoxicological risk assessment in soils contaminated by Pb and As 20 years after a mining spill

This study evaluates the potential toxicity of the soils of the Guadiamar Green Corridor (GGC) affected by the Aznalcóllar mine spill (Andalusia, Spain), one of the most important mining accidents in Europe in recent decades. Twenty years after the accident, although the area is considered to be recovered, residual contamination in soils persists, and the bioavailability of some contaminants, such as As, is showing trends of increasing. Therefore, the potential residual toxicity in 84 soil samples was evaluated by bioassays with lettuce (Latuca sativa L.), earthworms (Eisenia andrei) and determining the microbial activity by basal respiration and metabolic quotient. The selected soils sampled along the GGC were divided into 4 types according to their physicochemical properties. In the closest part of the mine two soil types appear (SS1 and SS2), originally decarbonated and loamy, with a reduction in lettuce root elongation of 57% and 34% compared to the control, as well as a the highest metabolic quotient (23.9 and 18.1 ng Cc_O2 μg Cmicrob^-1 h^-1, respectively) with the highest risk of Pb and As toxicity. While, located in the middle and final part of the affected area of the spill (SS3 and SS4), soils presented alkaline pH, finer textures and the lowest metabolic quotient (<9.5 ng Cc_O2 μg Cmicrob^-1 h^-1). In addition, due to Pb and As exceeded the Guideline values established in the studied area, the human toxicity risk was determined according to US-EPA methodology. Although the total contents were higher than the Guidelines established, the obtained hazard quotients for both contaminants were less than one, so the risk for human health was discarded. However, monitoring over time of the toxicity risks of the GGC soils would be advisable, especially due to the existence of areas where residual contamination persist, and soil hazard quotient obtained for As in children was higher and close to unity.

A meta-analysis-based evaluation of metallic element accumulation in earthworms

The responses of earthworms to excess soil element concentrations are well studied. However, published information on the metallic element accumulation in individuals is controversial. In this paper, the published data on earthworm As, Cd, Cr, Cu, Ni, Pb, and Zn whole body concentrations were evaluated in individuals collected from contaminated and uncontaminated (control) soils, using meta-analyses. The role of soil pH and exposure time as potential influencing factors on metal accumulation was also assessed. Based on the evaluations, the accumulation of each metallic element was significantly (p < 0.05) more intensive in individuals collected from contaminated soils than in ones from control soils, with minor differences in the order of accumulation intensity among the studied metallic elements. Further, major interspecific differences were indicated in the accumulation, with different species being the most intensive accumulators for individual metallic elements. Among the studied metals, Cu concentration in earthworm bodies increased significantly with increasing soil pH. As for the exposure time-dependent accumulation, Pb concentration was found to decrease significantly with time in whole body tissues of earthworms. These results suggested a high variability in metal- and species-specific accumulation-excretion patterns of earthworms, influenced also by other external factors. Based on the results highlighted in this meta-analysis, accumulation schemes raise the need for further analyses involving other additional variables (e.g., soil type, organic matter content, climatic condition) to get a better understanding of element cycle-earthworm relations.

Evidence for the metal resistance of earthworm Eisenia fetida across generations (F1 and F2) under laboratory metal exposure

Environmental stressors are persistent but most toxicological studies always evaluate the risk via short-term acute toxicity, while continuous toxicity and biological resistance across generations are relatively unknown. Here, earthworm Eisenia fetida was laboratory-reared and exposed to historically contaminated soils with an increasing metal gradient (CK, LM and HM), to investigate cross-generation toxicity and resistance of F1 and F2 worms. The results elucidated that biomass and juvenile hatching rate of F2 E. fetida showed maximum decreases of 20.8% and 38.5% than those of F1, which indicated severer toxicity of earthworm offspring. However, metal bioaccumulation in F2 E. fetida showed maximum increases of 150%, 49.2%, 19.7% and 25.5% than F1 for Cd, Cu, Zn and Pb, respectively. F2 E. fetida suffered less oxidative stress because the activities of superoxide dismutase (SOD), peroxidase (POD), glutathione (GSH), and malondialdehyde (MDA) contents were basically lower than that of F1. Meanwhile, the detoxification genes of metallothionein and heat shock protein 70 in F2 E. fetida showed maximum of 296% and 78.9% up-regulations, respectively, which suggested greater metal resistance of F2 E. fetida. This study confirmed the cross-generation toxicity and resistance of earthworms, which provides novel insights to reveal specific contaminant risks from longer lifecycles. CAPSULE: Earthworms under cross-generation exposure can develop metal resistance despite suffering worse toxicity effects.

Soil Contamination and Bioaccumulation of Heavy Metals by a Tropical Earthworm Species (Alma nilotica) at Informal E-Waste Recycling Sites in Douala, Cameroon

Soil contamination at electronic waste (e-waste) recycling sites is pervasive, though many locations have yet to be studied. While such contamination can present risks to soil organisms, little is known on the risks to native species. The objective of the present study was to assess soil contamination by heavy metals at e-waste recycling sites, and the potential of Alma nilotica, a native earthworm species, to bioaccumulate these metals. Soil samples collected from eight informal e-waste recycling sites and two non-e-waste sites in Douala, Cameroon, were analyzed for metal content. Metal concentrations in earthworm juveniles exposed to the soils for 21 days followed by a 14-day post-exposure period were measured weekly. Mean soil metal concentrations at e-waste sites ranked as Cu > Pb > Zn > Hg > Ni > As > Cd > Co > Cr. Based on contamination factors, soil contamination ranged from "moderate" (Cr), through "considerable" (Co and Cd), to "very high" for the rest of the metals. Based on the modified degree of contamination and risk index, all e-waste sites had "ultra-high" contamination with Ni, Pb, and Zn posing very high ecological risks and Bonaberi being the most contaminated site. There was a positive correlation between soil metal concentrations and metal accumulation (retention) by eathworms, but Hg and Co had the highest bioaccumulation factors (BAFs) despite having low soil concentrations. These results document that e-waste sites in Douala are contaminated with metals and that native earthworm species can bioaccumulate the studied metals at levels that could account for the toxic effects earlier recorded. With e-waste recycling growing worldwide, there is a need for more data, especially from understudied locations. Environ Toxicol Chem 2022;41:356-368. © 2021 SETAC.

Metallothionein dependent-detoxification of heavy metals in the agricultural field soil of industrial area: Earthworm as field experimental model system

Earthworms are known to reclaim soil contamination and maintain soil health. In the present study, the concentration of DTPA extractable heavy metals, Cd, Cu, Cr, Pb, and Zn in vermicasts and tissues of the earthworms (anecic: Lampito mauritii; epigeic: Drawida sulcata) collected from the soils of four different industrial sites, Site-I (Sago industry), Site-II (Chemplast industry), Site-III (Dairy industry) and Site-IV (Dye industry) have been studied. The heavy metals in industrial soils recorded were 0.01-326.42 mg kg^-1 with higher Cu, Cr, and Zn contents while the vermicasts showed lower heavy metal loads with improved physicochemical properties and elevated humic substances. The higher humic substances dramatically decreased the heavy metals in the soil. The bioaccumulation factors of heavy metals (mg kg^-1) are in the order: Zn (54.50) > Cu (17.43) > Cr (4.54) > Pb (2.24) > Cd (2.12). The greatest amount of metallothionein protein (nmol g^-1) was recorded in earthworms from Site-IV (386.76) followed by Site-III (322.14), Site-II (245.82), and Site-I (232.21). Drawida sulcata can produce a considerable amount of metallothionein protein than Lampito mauritii as the metallothionein production is dependent upon the presence of pollutants. The molecular docking analysis indicates a binding score of 980 for Cd, Cr and Cu, and 372 for Zn. Pb may bind with a non-metallothionein protein of earthworms and bio-accumulated in the internal chloragogenous tissues. Metallothionein neutralizes the metal toxicity and controls the ingestion of essential elements.

Toxicity of soil antimony to earthworm Eisenia fetida (Savingy) before and after the aging process

Information on soil antimony (Sb) toxicity to earthworm Eisenia fetida (Savingy) is limited. This ecotoxicology study was designed to quantify the soil Sb toxicity to earthworm E. fetida before and after aging process, establishing dose-effect relationship between Sb content and mortality. Results of the avoidance test and acute test showed that the values of net avoidance response, escape rate and mortality were generally decreased in aged treatment compared to that in fresh treatment, respectively from 93.33% to 66.67%, 36.67% to 13.33% and 100% to 53.33% (15 d) taking TL800 (treatment level of 800 mg/kg) for example, meanwhile the values of median lethal content (LC₅₀) at 72 h, 7 d and 15 d were respectively increased from 355.27 mg/kg to 2324.55 mg/kg, 322.19 mg/kg and 1743.19 mg/kg and 282.74 mg/kg to 745.94 mg/kg, indicating that aging process could reduce the Sb acute toxicity to earthworm. According to a three-step sequential extraction procedure, the bioavailable Sb ranged from 24.45% to 43.24% and 16.97% to 27.70% in fresh treatment and aged treatment, respectively, and the mortality of earthworm for 24 h decreased with the decrease of the content of mild acid-soluble antimony (which decreased averagely from 23.09% to 14.00%), which was more suited to assess Sb toxicity. This is the first report that confirms the toxicity of soil Sb to earthworm E. fetida as well as the considering of aging process and speciation.

Impact assessment of legacy wastes from ancient mining activities on current earthworm community

Mineral resource exploitation by human societies throughout history led to the deposit of mining and smelting wastes and the subsequent contamination of surrounding soils by trace metals. After several centuries, the impact of these legacy hazardous wastes may remain a cause of environmental concern, especially for indigenous soil invertebrate populations such as earthworms. Therefore, we conducted a passive biomonitoring campaign in a former metallurgical district (Vosges Mountains, eastern France). According to community descriptors, we evidenced a significant decrease of anecic and endogeic earthworm density in the former mining stations. To link these results to soil contamination and bioaccumulation levels in earthworm tissues, we propose an original modelling approach using nonlinear mixed-effects regression models. Beyond a dose-response relationship between metal internal concentrations and their levels in soils, we highlighted contrasted behaviors according to ecological groups (epianecics and endogeics most impacted). We interpreted these results in relation to some eco-physiological features without completely exclude the influence of textural characteristics of soil, especially for deep-burrowing species such as anecic strict. Nonetheless, the presence of earthworm populations currently living in highly contaminated sites and handling elevated internal concentrations raises the question of the acquisition of genetic adaptive traits and the trophic transfers of metals.

Synthesis of earthworm trace metal uptake and bioaccumulation data: Role of soil concentration, earthworm ecophysiology, and experimental design

Trace metals can be essential for organo-metallic structures and oxidation-reduction in metabolic processes or may cause acute or chronic toxicity at elevated concentrations. The uptake of trace metals by earthworms can cause transfer from immobilized pools in the soil to predators within terrestrial food chains. We report a synthesis and evaluation of uptake and bioaccumulation empirical data across different metals, earthworm genera, ecophysiological groups, soil properties, and experimental conditions (metal source, uptake duration, soil extraction method). Peer-reviewed datasets were extracted from manuscripts published before June 2019. The 56 studies contained 3513 soil-earthworm trace metal concentration paired data sets across 11 trace metals (As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Sb, U, Zn). Across all field and laboratory experiments studied, the median concentrations of Hg, Pb, and Cd in earthworm tissues that were above concentrations known to be hazardous for consumption by small mammals and avian predators but not for Cu, Zn, Cr, Ni, and As. Power regressions show only Hg and Cd earthworm tissue concentrations were well-correlated with soil concentrations with R² > 0.25. However, generalized linear mixed-effect models reveal that earthworm concentrations were significantly correlated with soil concentrations for log-transformed Hg, Cd, Cu, Zn, As, Sb (p < 0.05). Factors that significantly contributed to these relationships included earthworm genera, ecophysiological group, soil pH, and organic matter content. Moreover, spiking soils with metal salts, shortening the duration of exposure, and measuring exchangeable soil concentrations resulted in significantly higher trace metal uptake or greater bioaccumulation factors. Our results highlight that earthworms are able to consistently bioaccumulate toxic metals (Hg and Cd only) across field and laboratory conditions. However, future experiments should incorporate greater suites of trace metals, broader genera of earthworms, and more diverse laboratory and field settings to generate data to devise universal quantitative relationships between soil and earthworm tissue concentrations.

Chilean regulations on metal-polluted soils: The need to advance from adapting foreign laws towards developing sovereign legislation

Chile as a major international Cu producer faces serious soil contamination issues in mining areas. Currently Chile does not have any specific law governing the maximum permissible concentrations of metals in soils to protect ecosystems and human health. Chile heavily relies on the use of environmental laws of 14 foreign countries; the choice of the country depends on the similarity of its environmental conditions with those in Chile. In this study, we used an online database to compare the similarity of Chilean rocks to those in foreign countries. Likewise, we performed soil sampling and determined the background concentrations of Cu, As, Pb, and Zn in soils of the Aconcagua basin, the largest river basin in the Valparaiso Region of central Chile. The results showed that geochemical patterns in Chile have the greatest resemblance to New Zealand, Mexico, and Italy. The background Cu concentration in the Aconcagua basin (134 mg kg^-1) exceeded the legislated limits of New Zealand (100 mg kg^-1) and Italy (120 mg kg^-1), whereas the background Zn concentration (200 mg kg^-1) exceeded the legislated limit of Italy (150 mg kg^-1). Due to the elevated natural abundance of Cu and Zn in Chile, international laws should not be applied in Chile for the assessment of soil contamination. In addition, we assessed ecological risk using the results of our previous studies obtained by analyzing native field-contaminated soils of the Valparaiso region. In the Aconcagua basin, Cu posed high risk for plants in 11% of the samples, whereas As posed high risk for earthworms in 48% of the samples. We suggest that future studies are required to search for other organisms that can serve as biomarkers of metal toxicity because our previous studies were limited to plants and earthworms. Importantly, As posed high risk to human health in 25% of the samples in our study. There is a need for future studies to demonstrate empirically an association between soil As and children's blood As in order to establish the national threshold values of soil As to protect human health. We conclude that there is an urgent need in Chile to advance from the current approach of adapting foreign laws to developing Chilean sovereign environmental legislation.

Multiple heavy metal tolerance and removal by an earthworm gut fungus Trichoderma brevicompactum QYCD-6

Fungal bioremediation is a promising approach to remove heavy-metal from contaminated water. Present study examined the ability of an earthworm gut fungus Trichoderma brevicompactum QYCD-6 to tolerate and remove both individual and multi-metals. The minimum inhibitory concentration (MIC) of heavy metals [Cu(II), Cr(VI), Cd(II) and Zn(II)] against the fungus was ranged 150–200 mg L⁻¹ on composite medium, and MIC of Pb(II) was the highest with 1600 mg L⁻¹ on potato dextrose (PD) medium. The Pb(II) presented the highest metal removal rate (97.5%) which mostly dependent on bioaccumulation with 80.0%, and synchronized with max biomass (6.13 g L⁻¹) in PD medium. However, on the composite medium, the highest removal rate was observed for Cu(II) (64.5%). Cellular changes in fungus were reflected by TEM analysis. FTIR and solid-state NMR analyses indicated the involvement of different functional groups (amino, carbonyl, hydroxyl, et al.) in metallic biosorption. These results established that the earthworm-associated T. brevicompactum QYCD-6 was a promising fungus for the remediation of heavy-metal wastewater.

Influence of earthworm bioturbation on metals phytoavailability and human gastric bioaccessibility

At the global scale, urban agriculture is increasingly developing in cities due to demographic growth and sustainable food concerns. But, urban soils are frequently polluted with metals. In urban gardens, organic matter is also commonly added both to valorize organic household waste and to promote biophysicochemical fertility. As earthworms promote the decomposition and the recycling of soil organic matter, they can also influence the biogeochemical cycle of metals in urban polluted soils. In order to produce safe vegetables in urban areas, it is crucial to highlight the mechanisms involved in complex soil-earthworm-plant ecosystems. An experiment was set up to examine these relationships using lettuce cultivated in controlled conditions with RHIZOtest® devices. Thanks to the RHIZOtest® devices, metal transfer and bioaccessibility were for the first time compared for urban polluted soil without (1-urban soil polluted with Pb, Cd, Cu, and Zn: essential or toxic metals currently found in environment, SNB) and with bioturbation (2-this metal-polluted soil subjected to earthworm bioturbation, SB) and earthworm casts (3-earthworm casts produced in this polluted soil and naturally enriched in organic matter and microorganisms, T). Metal concentration, phytoavailability, and human gastric bioaccessibility were determined in the different samples. Results showed that earthworm bioturbation increased the phytoavailability of all the metals. For the experimental condition SB, the phytoavailability of metals was increased up to 75% compared to SNB. In addition, surprisingly, metal phytoavailability was always superior in SB compared to earthworm casts (T). Moreover, earthworms led to an increase in Zn gastric bioaccessibility up to 10% in the soils in the same way as for phytoavailability, meaning Zn bioaccessibility in SB > T > SNB, whereas it remained unchanged in the lettuces. These data are important to promote sustainable agriculture activities in urban areas; actually, databases concerning different experimental conditions are needed to develop decision support tools.

Species-dependent effects of earthworms on the fates and bioavailability of tetrabromobisphenol A and cadmium coexisted in soils

The activity of e-waste recycling often causes the combined pollution of tetrabromobisphenol A (TBBPA) and cadmium (Cd) in soils. In this study, the effects of their co-existence on each other's fate, further reflecting the bioavailability, were analyzed in the presence of two ecologically different earthworm species, endogeic Metaphire guillelmi and epigeic Eisenia fetida. Mineralization of ¹⁴C-TBBPA combined with 10 mg Cd kg^-1 was suppressed by the presence of M. guillelmi, whereas a facilitating effect was produced by the combination of 1 mg Cd kg^-1 in the soil-E. fetida system after a 14-day exposure. The uptake of ¹⁴C-TBBPA by M. guillelmi (17% of initial amount) and by E. fetida (10%) dominantly contributed to significant (P < 0.05) decrease of extractable (more bioavailable) ¹⁴C residues in soils both with and without Cd spiked, while the mineralization of ¹⁴C-TBBPA in the soils was negligible (<0.4%). Meanwhile the amendments of the two earthworm species exerted different impact on ¹⁴C distribution in bound residues. In general, co-exposure to Cd did not significantly (P > 0.05) influence the accumulation and metabolism of TBBPA in the earthworms. Both earthworms accumulated only ~7% of Cd in soil, however, the bioavailable Cd determined by the diffusive gradients in thin films technique declined by ~46% in the presence of M. guillelmi, and a much smaller decrease was determined in the presence of E. fetida. Amendment of TBBPA at environmental levels did not alter the accumulation and subcellular distribution of Cd in both earthworms unless that at high doses. The results highlighted the importance of considering the difference of the earthworm species and the interaction of pollutants in soil-risk assessments of such combined contamination. CAPSULE: M. guillelmi displayed greater effect on the fate of TBBPA and Cd co-existed in soils than E. fetida, while the accumulation, metabolism, or distribution of the two pollutants in earthworms did not significantly alter due to interactions between the two pollutants.

Influence of metal-contamination on distribution in subcellular fractions of the earthworm (Metaphire californica) from Hunan Province, China

Earthworms have the ability to accumulate of heavy metals, however, there was few studies that addressed the metals in earthworm at subcellular levels in fields. The distributions of metals (Cd, Cu, Zn, and Pb) in subcellular fractions (cytosol, debris, and granules) of earthworm Metaphire californica were investigated. The relationship between soil metals and earthworms were analyzed to explain its high plasticity to inhabit in situ contaminated soil of Hunan Province, south China. The concentration of Cd in subcellular compartments showed the same pattern as Cu in the order of cytosol > debris > granules. The distribution of Zn and Pb in earthworms indicated a similar propensity for different subcellular fractions that ranked as granules > debris > cytosol for Zn, and granules > cytosol > debris for Pb. The internal metal concentrations in earthworms increased with the soil metals (p<0.05). Significant positive correlations were found between soil Cd and Cd concentrations in cytosol and debris (p<0.01). Moreover, the soil Pb concentration significantly influenced the Pb concentrations in cytosol and debris (p<0.01), similar to that of Cd. The soil Cu concentrations was only associated with the Cu in granules (p<0.05). Soil Zn concentrations correlated with the Zn concentrations in each subcellular fraction (p<0.05). Our results provide insights into the variations of metals partitioning in earthworms at subcellular levels and the relationships of soil metals, which could be one of the detoxification strategies to adapt the long-term contaminated environment.

Effects of combined exposure to perfluoroalkyl acids and heavy metals on bioaccumulation and subcellular distribution in earthworms (Eisenia fetida) from co-contaminated soil

The effects of combined exposure to perfluoroalkyl acids (PFAAs) and heavy metals (HMs) including cadmium (Cd), copper (Cu), zinc (Zn), nickel (Ni), and lead (Pb) on earthworms (Eisenia fetida) were investigated. The results have demonstrated that the concentrations of labile acid exchangeable Cd, Zn, Ni, Pb, and Cu in soil were enhanced in addition of PFAAs. With PFAAs, the uptake of Cd, Zn, Ni, Pb, and Cu in earthworms was increased compared to those without PFAAs with the order of Cd > Zn > Pb > Ni > Cu. In the presence of HMs, the average biota-to-soil accumulation factors (BSAFs) of PFAAs in earthworms were decreased by 0.498-0.729 times for perfluorooctane sulfonate (PFOS) and 0.606-0.978 times for perfluorooctanoic acid (PFOA), indicating decrease rates of PFOS were higher than those of PFOA. And different levels of HMs led to insignificant different responses on the inhibiting effects of PFAAs uptake in earthworms. The increase of Cd in fraction C (associated with cytosol) and decrease of PFAAs in fraction C and fraction P (associated with tissue fragments, cell membranes, and intact cells) especially for fraction C were revealed when they were combined, suggesting cytosolic PFAAs and Cd were susceptibly mutual effected. This study indicated that PFAAs and metals mutually affected their bioaccumulation and subcellular distribution in earthworms, which will help to understand the fate and risks of PFAAs and metals in co-contaminated soil.

Structural equation model of the relationship between metals in contaminated soil and in earthworm (Metaphire californica) in Hunan Province, subtropical China

Earthworms have the ability to take up heavy metals in soil and partition them in different subcellular compartments. In this study, we used a structural equation model (SEM) to investigate the two-step causal relationship between environmental availability (EA) and environmental bioavailability (EB) of heavy metals (Cd, Cu, Zn, and Pb), as reflected by their levels in soil fractions and in earthworms from field-contaminated areas in Southern China. In the SEM, the correlation between EA and EB reflected the bioavailability of Cd, Zn, and Pb. For Cd, the causal relationship between the latent variables EA and EB was reflected by DTPA fractions in soil as well as by earthworm internal and subcellular cytosol fractions. The extractable and oxidizable fractions of Zn in soil influenced Zn concentrations in the cytosol and debris. The DTPA and reducible Pb fractions were bioavailable to earthworm internal Pb concentrations and those in cytosol fractions. These results implied that the DTPA, extractable, oxidizable, or reducible fractions of different metals could be the bioavailable sources to earthworm internal metals and partitioned in their subcellular compartments.

Differences in the bioaccumulation of selenium by two earthworm species (Pheretima guillemi and Eisenia fetida)

Information on the bioaccumulation of selenium (Se) in soil invertebrates (e.g. earthworms) is rather scarce. In the present study, bioaccumulation of Se in two eco-physiologically different earthworms, namely anecic Pheretima guillemi and epigeic Eisenia fetida, was determined after 28 days exposure to a successive doses of Se-spiked soil, specifically 0.5, 5, 50, and 200 μg Se g^-1 soil. The results showed that Se concentration in earthworms elevated with increasing exposure levels, and maximums were up to 54.6 and 83.0 μg g^-1 dry weight in Pheretima guillemi and Eisenia fetida, respectively, after 4 weeks exposure to 200 μg Se g^-1 soil. Exposure to Se caused significant inhibition on earthworm growth, with the fresh weight loss ranging from 8.9% to 80.5%. Bioaccumulation factors (BAFs), empirically-derived and non-steady state, ranged from 0.12 to 4.17 and generally declined at higher exposure levels. Moreover, BAFs of Pheretima guillemi were higher than those of Eisenia fetida in low-dose Se-spiked soils, but the opposite was true in high-dose soils, indicating there is a species-specific response to exposure of Se between different earthworms. Further research is thus needed to reveal the accumulation pattern of Se in a wider range of earthworm species other than Eisenia fetida, which allows a better risk assessment of excessive Se to soil invertebrates and higher order organisms.

Opportunities and risks of biofertilization for leek production in urban areas: Influence on both fungal diversity and human bioaccessibility of inorganic pollutants

The influence of biofertilization with arbuscular mycorrhizal fungi (AMF) on trace metal and metalloids (TM) - Pb, Cd and Sb - uptake by leek (Allium porrum L.) grown in contaminated soils was investigated. The effect of biofertilization on human bioaccessibility of the TM in the plants was also examined. Leek were cultivated in one soil with geogenic TM sources and one soil with anthropogenic TM, to assess the influence of pollutant origin on soil-plant transfer. Leek were grown for six months on these contaminated soils, with and without a local AMF based biofertilizer. Fungal communities associated with leek roots were identified by high throughput sequencing (illumina Miseq®) metagenomic analysis. The TM compartmentation was studied using electron microscopy in plants tissues. In all the soils, biofertilization generated a loss of diversity favoring the AM fungal species Rhizophagus irregularis, which could explain the observed modification of metal transfer at the soil-AMF-plant interface. The human bioaccessibility of Sb increased in biofertilized treatments. Consequently, this latter result highlights a potential health risk of the use of this fertilization technique on contaminated soil since further field investigation is performed to better understand the mechanisms governing (1) the effect of AMF on TM bioaccessibility and (2) the evolution of AMF communities in contaminated soils.

Bioturbation effects on bioaccumulation of cadmium in the wetland plant Typha latifolia: A nature-based experiment

The development of efficient bioremediation techniques to reduce aquatic pollutant load in natural sediment is one of the current challenges in ecological engineering. A nature-based solution for metal bioremediation is proposed through a combination of bioturbation and phytoremediation processes in experimental indoor microcosms. The invertebrates Tubifex tubifex (Oligochaeta Tubificidae) was used as an active ecological engineer for bioturbation enhancement. The riparian plant species Typha latifolia was selected for its efficiency in phyto-accumulating pollutants from sediment. Phytoremediation efficiency was estimated by using cadmium as a conservative pollutant known to bio-accumulate in plants, and initially introduced in the overlying water (20μg Cd/L of cadmium nitrate - Cd(NO₃)₂·4H₂O). Biological sediment reworking by invertebrates' activity was quantified using luminophores (inert particulates). Our results showed that bioturbation caused by tubificid worms' activity followed the bio-conveying transport model with a downward vertical velocity (V) of luminophores ranging from 16.7±4.5 to 18.5±3.9cm·year^-1. The biotransport changed the granulometric properties of the surface sediments, and this natural process was still efficient under cadmium contamination. The highest value of Cd enrichment coefficient for plant roots was observed in subsurface sediment layer (below 1cm to 5cm depth) with tubificids addition. We demonstrated that biotransport changed the distribution of cadmium across the sediment column as well as it enhanced the pumping of this metal from the surface to the anoxic sediment layers, thereby increasing the bioaccumulation of cadmium in the root system of Typha latifolia. This therefore highlights the potential of bioturbation as a tool to be considered in future as integrated bioremediation strategies of metallic polluted sediment in aquatic ecosystems.

Important Issues in Ecotoxicological Investigations Using Earthworms

The importance and beneficial effects of earthworms on soil structure and quality is well-established. In addition, earthworms have proved to be important model organisms for investigation of pollutant effects on soil ecosystems. In ecotoxicological investigations effects of various pollutants on earthworms were assessed. But some important issues regarding the effects of pollutants on earthworms still need to be comprehensively addressed. In this review several issues relevant to soil ecotoxicological investigations using earthworms are emphasized and guidelines that should be adopted in ecotoxicological investigations using earthworms are given. The inclusion of these guidelines in ecotoxicological studies will contribute to the better quantification of impacts of pollutants and will allow more accurate prediction of the real field effects of pollutants to earthworms.

Uptake route and resulting toxicity of silver nanoparticles in Eisenia fetida earthworm exposed through Standard OECD Tests

Despite the increasing interest in silver nanoparticles toxicity still few works dealt with the hazards of nanosized Ag in soils (either dissolved in pore water or coupled to colloids) although disposal of biosolids in landfills has been reported as the major source of silver nanoparticles in terrestrial environments. Presently, Eisenia fetida was used to assess the toxicity of 5 nm sized PVP-PEI coated silver nanoparticles in soil through the implementation of different exposure media Standard Toxicity Tests (Paper Contact and Artificial Soil -OECD-207- and Reproduction -OECD-222- Tests) together with cellular biomarkers measured in extruded coelomocytes. In order to decipher the mode of action of silver nanoparticles in soil and the uptake routes in earthworms, special attention was given to the Ag accumulation and distribution in tissues. High Ag accumulation rates, weight loss, and mortality due to the disruption of the tegument could be the result of a dermal absorption of Ag ions released from silver nanoparticles (Paper Contact Test). However, autometallography showed metals mainly localized in the digestive tract after Artificial Soil Test, suggesting that Ag uptake occurred mostly through soil ingestion. That is, silver nanoparticles attached to soil colloids seemed to be internalized in earthworms after ingestion of soil and transferred to the digestive gut epithelium where at high doses they have triggered severe effects at different levels of biological complexity.

Soil microbial respiration and PICT responses to an industrial and historic lead pollution: a field study

We performed a field investigation to study the long-term impacts of Pb soil contamination on soil microbial communities and their catabolic structure in the context of an industrial site consisting of a plot of land surrounding a secondary lead smelter. Microbial biomass, catabolic profiles, and ecotoxicological responses (PICT) were monitored on soils sampled at selected locations along 110-m transects established on the site. We confirmed the high toxicity of Pb on respirations and microbial and fungal biomasses by measuring positive correlations with distance from the wall factory and negative correlation with total Pb concentrations. Pb contamination also induced changes in microbial and fungal catabolic structure (from carbohydrates to amino acids through carboxylic malic acid). Moreover, PICT measurement allowed to establish causal linkages between lead and its effect on biological communities taking into account the contamination history of the ecosystem at community level. The positive correlation between qCO2 (based on respiration and substrate use) and PICT suggested that the Pb stress-induced acquisition of tolerance came at a greater energy cost for microbial communities in order to cope with the toxicity of the metal. In this industrial context of long-term polymetallic contamination dominated by Pb in a field experiment, we confirmed impacts of this metal on soil functioning through microbial communities, as previously observed for earthworm communities.

Risk assessment of metals and PAHs for receptor organisms in differently polluted areas in Slovenia

Samples from receptor organisms (small mammals, passerine birds) and their food sources (herbaceous plants, leaves and fruits of wood plants, earthworms) were collected during 2011-2014 from the vicinity of a former lead smelter, from the vicinity of the largest Slovenian thermal power plant, from along a state road and also from a reference area. The samples were then analysed to determine the degree of contamination with the metals (Pb, Cd, Zn, Hg, Cu, Mo) and with polycyclic aromatic hydrocarbons (PAHs). This study provides the first data on metal and PAH exposure to small mammals and passerine birds in southeast Europe, focussing on the transfer of metals and PAHs through the food chain and on risk assessment for differently polluted areas in Slovenia. The results indicate that: (i) earthworms and herbaceous plants (especially roots) can be a source of metal exposure for organisms higher in the food chain; (ii) a risk from Pb and Cd (HQ > 1) in the vicinity of the former lead smelter exists for Myodes glareolus feeding in part on roots and for Apodemus flavicollis and Parus major feeding in part on earthworms; and (iii) mean Pb and Cd concentrations in the liver of small mammal species inhabiting the vicinity of the lead smelter reach effect concentrations in a significant proportion of the specimens (Pb: 40%, Cd: 67%); (iv) the results for P. major confirm that the study area is exposed to Pb, Cd, Hg; (v) metals contribute the major part of the total risk for receptor organisms from vicinity of lead smelter. On the contrary, the risk of PAHs for small mammals trapped close to the state road is insignificant. We can summarize, that the hazards experienced by the local ecosystem due to metal exposure may persist for decades in the vicinity of large emission sources (especially smelters).

Field isotopic study of lead fate and compartmentalization in earthworm-soil-metal particle systems for highly polluted soil near Pb recycling factory

Earthworms are important organisms in soil macrofauna and play a key role in soil functionality, and consequently in terrestrial ecotoxicological risk assessments. Because they are frequently observed in soils strongly polluted by metals, the influence of earthworm bioturbation on Pb fate could therefore be studied through the use of Pb isotopes. Total Pb concentrations and isotopic composition ((206)Pb, (207)Pb and (208)Pb) were then measured in earthworms, casts and bulk soils sampled at different distance from a lead recycling factory. Results showed decreasing Pb concentrations with the distance from the factory whatever the considered matrix (bulk soils, earthworm bodies or cast samples) with higher concentrations in bulk soils than in cast samples. The bivariate plot (208)Pb/(206)Pb ratios versus (206)Pb/(207)Pb ratios showed that all samples can be considered as a linear mixing between metallic process particulate matter (PM) and geochemical Pb background. Calculated anthropogenic fraction of Pb varied between approximately 84% and 100%. Based on Pb isotopic signatures, the comparison between casts, earthworms and bulk soils allowed to conclude that earthworms preferentially ingest the anthropogenic lead fraction associated with coarse soil organic matter. Actually, soil organic matter was better correlated with Pb isotopic ratios than with Pb content in soils. The proposed hypothesis is therefore a decrease of soil organic matter turnover due to Pb pollution with consequences on Pb distribution in soils and earthworm exposure. Finally, Pb isotopes analysis constitutes an efficient tool to study the influence of earthworm bioturbation on Pb cycle in polluted soils.

Antimony bioavailability: knowledge and research perspectives for sustainable agricultures

The increasing interest in urban agriculture highlights the crucial question of crop quality. The main objectives for environmental sustainability are a decrease in chemical inputs, a reduction in the level of pollutants, and an improvement in the soil's biological activity. Among inorganic pollutants emitted by vehicle traffic and some industrial processes in urban areas, antimony (Sb) is observed on a global scale. While this metalloid is known to be potentially toxic, it can transfer from the soil or the atmosphere to plants, and accumulate in their edible parts. Urban agriculture is developing worldwide, and could therefore increasingly expose populations to Sb. The objective of this review was in consequences to gather and interpret actual knowledge of Sb uptake and bioaccumulation by crops, to reveal investigative fields on which to focus. While there is still no legal maximal value for Sb in plants and soils, light has to be shed on its accumulation and the factors affecting it. A relative absence of data exists about the role of soil flora and fauna in the transfer, speciation and compartmentation of Sb in vegetables. Moreover, little information exists on Sb ecotoxicity for terrestrial ecosystems. A human risk assessment has finally been reviewed, with particular focus on Sb bioaccessibility.

Effects of historic metal(loid) pollution on earthworm communities

The effects of metal(loid)s (Pb, Cd, Cu, Zn, As and Sb) from atmospheric fallout on earthworm communities were investigated in a fallow meadow located close to a 60-year-old lead recycling factory. We examined abundance and species diversity as well as the ratio of adult-to-juvenile earthworms, along five 140 m parallel transects. The influence of soil pollution on the earthworm community at the plot scale was put in context by measuring some physico-chemical soil characteristics (OM content, N content, pH), as well as total and bioavailable metal(loid) concentrations. Earthworms were absent in the highly polluted area (concentration from 30,000 to 5000 mg Pb·kg(-1) of dried soil), just near the factory (0-30 m area). A clear and almost linear relationship was observed between the proportion of juvenile versus mature earthworms and the pollution gradient, with a greater proportion of adults in the most polluted zones (only adult earthworms were observed from 30 to 50 m). Apporectodea longa was the main species present just near the smelter (80% of the earthworms were A. longa from 30 to 50 m). The earthworm density was found to increase progressively from five individuals·m(-2) at 30 m to 135 individuals·m(-2) at 140 m from the factory. On average, metal(loid) accumulation in earthworm tissues decreased linearly with distance from the factory. The concentration of exchangeable metal(loid)s in earthworm surface casts was higher than that of the overall soil. Finally, our field study clearly demonstrated that metal(loid) pollution has a direct impact on earthworm communities (abundance, diversity and proportion of juveniles) especially when Pb concentrations in soil were higher than 2050 mg·kg(-1).

Metallothionein gene expression differs in earthworm populations with different exposure history

Metals are persistent pollutants in soils that can harm soil organisms and decrease species diversity. Animals can cope with metal contamination with the help of metallothioneins, small metal-binding proteins involved in homeostasis and detoxification of metals. We studied the expression of metallothionein with qPCR in a small, epigeic earthworm, Dendrobaena octaedra. We compared expression patterns and metal body content in earthworms collected from two sites with different metal contamination histories: Harjavalta, contaminated by a Cu-Ni smelter operational for over 50 years, and Jyväskylä, an uncontaminated site. Earthworms from both sites were also experimentally exposed to different concentrations of Cu (control, 50, 100 or 200 mg/kg) or Zn (control, 75, 150 or 300 mg/kg) for 7, 14 or 28 days to determine if there is a time related dose-response in gene expression. Population comparison showed that metallothionein expression was higher in earthworms from the contaminated site. In the exposure experiment, exposure time affected expression, but only in the earthworms from the uncontaminated site, suggesting that there is a delay in the metallothionein response of earthworms in this population. In contrast, earthworms from the contaminated site showed higher and constant levels of metallothionein expression at all exposure concentrations and durations. The constant metallothionein expression in earthworms from the contaminated site suggests that inducibility of metallothionein response could be lost in earthworms with metal exposure history. Adaptation of D. octaedra to metal exposure could explain the differences between the populations and explain the persistence of this species in contaminated forest soils.

Foliar uptake and metal(loid) bioaccessibility in vegetables exposed to particulate matter

At the global scale, high concentrations of particulate matter (PM) enriched with metal(loid)s are currently observed in the atmosphere of urban areas. Foliar lead uptake was demonstrated for vegetables exposed to airborne PM. Our main objective here was to highlight the health risk associated with the consumption of vegetables exposed to foliar deposits of PM enriched with the various metal(loid)s frequently observed in the atmosphere of urban areas (Cd, Sb, Zn and Pb). Leaves of mature cabbage and spinach were exposed to manufactured mono-metallic oxide particles (CdO, Sb2O3 and ZnO) or to complex process PM mainly enriched with lead. Total and bioaccessible metal(loid) concentrations were then measured for polluted vegetables and the various PM used as sources. Finally, scanning electronic microscopy coupled with energy dispersive X-ray microanalysis was used to study PM-phyllosphere interactions. High quantities of Cd, Sb, Zn and Pb were taken up by the plant leaves. These levels depended on both the plant species and nature of the PM, highlighting the interest of acquiring data for different plants and sources of exposure in order to better identify and manage health risks. A maximum of 2% of the leaf surfaces were covered with the PM. However, particles appeared to be enriched in stomatal openings, with up to 12% of their area occupied. Metal(loid) bioaccessibility was significantly higher for vegetables compared to PM sources, certainly due to chemical speciation changes. Taken together, these results confirm the importance of taking atmospheric PM into account when assessing the health risks associated with ingestion of vegetables grown in urban vegetable crops or kitchen gardens.

Lead and cadmium phytoavailability and human bioaccessibility for vegetables exposed to soil or atmospheric pollution by process ultrafine particles

When plants are exposed to airborne particles, they can accumulate metals in their edible portions through root or foliar transfer. There is a lack of knowledge on the influence of plant exposure conditions on human bioaccessibility of metals, which is of particular concern with the increase in urban gardening activities. Lettuce, radish, and parsley were exposed to metal-rich ultrafine particles from a recycling factory via field atmospheric fallouts or polluted soil. Total lead (Pb) and cadmium (Cd) concentrations in of the edible plant parts and their human bioaccessibility were measured, and Pb translocation through the plants was studied using Pb isotopic analysis. The Pb and Cd bioaccessibility measured for consumed parts of the different polluted plants was significantly higher for root exposure (70% for Pb and 89% for Cd in lettuce) in comparison to foliar exposure (40% for Pb and 69% for Cd in lettuce). The difference in metal bioaccessibility could be linked to the metal compartmentalization and speciation changes in relation to exposure conditions. Metal nature strongly influences the measured bioaccessibility: Cd presents higher bioaccessibility in comparison to Pb. In the case of foliar exposure, a significant translocation of Pb from leaves toward the roots was observed. To conclude, the type of pollutant and the method of exposure significantly influences the phytoavailability and human bioaccessibility of metals, especially in relation to the contrasting phenomena involved in the rhizosphere and phyllosphere. The conditions of plant exposure must therefore be taken into account for environmental and health risk assessment.

Is there a relationship between earthworm energy reserves and metal availability after exposure to field-contaminated soils?

Generic biomarkers are needed to assess environmental risks in metal polluted soils. We assessed the strength of the relationship between earthworm energy reserves and metal availability under conditions of cocktail of metals at low doses and large range of soil parameters. Aporrectodea caliginosa was exposed in laboratory to a panel of soils differing in Cd, Pb and Zn total and available (CaCl2 and EDTA-extractable) concentrations, and in soil texture, pH, CEC and organic-C. Glycogen, protein and lipid contents were recorded in exposed worms. Glycogen contents were not linked to the explaining variables considered. Variable selection identified CaCl2 extractable metals concentrations and soil texture as the main factors affecting protein and lipid contents. The results showed opposite effects of Pb and Zn, high inter-individual variability of biomarkers and weak relationships with easily extractable metals. Our results support the lack of genericity of energy reserves in earthworms exposed to field-contaminated soils.

Earthworm bioturbation influences the phytoavailability of metals released by particles in cultivated soils

The influence of earthworm activity on soil-to-plant metal transfer was studied by carrying out six weeks mesocosms experiments with or without lettuce and/or earthworms in soil with a gradient of metal concentrations due to particles fallouts. Soil characteristics, metal concentrations in lettuce and earthworms were measured and soil porosity in the mesocosms was determined. Earthworms increased the soil pH, macroporosity and soil organic matter content due to the burying of wheat straw provided as food. Earthworm activities increased the metals concentrations in lettuce leaves. Pb and Cd concentrations in lettuce leaves can increase up to 46% with earthworm activities … These results and the low correlation between estimated by CaCl2 and EDTA and measured pollutant phytoavailability suggest that earthworm bioturbation was the main cause of the increase. Bioturbation could affect the proximity of pollutants to the roots and soil organic matter.

Longitudinal in vivo MR imaging of live earthworms

Earthworm (Oligochaeta, Lumbricidae) species are used widely in eco-toxicological tests especially with contaminated soils. These long-term tests are reliable, but a high sample size is needed. Magnetic resonance imaging (MRI) can produce fast, robust, sensitive, and longitudinal morphological results using a small sample size. Performing longitudinal in vivo examinations of earthworms using MRI requires the need for anesthetics to completely avoid earthworm's moving. Our goal was to develop a simple and non-invasive method to anesthetize earthworms for in vivo longitudinal imaging studies. We investigated a number of different anesthesia methods and found that propan-2-ol and its vapor was optimal. We used a commercial sequential nanoScan® PET/MRI system (Mediso Ltd, Hungary, Budapest) to explore feasibility of MR imaging in immobilized earthworms. It was possible to visualize via micro MRI the brain, gastrointestinal tract, seminal vesicles, calciferous gland (Morren gland), and main blood vessels of the circulatory system. Our findings show the possibilities to examine changes in morphology using MRI of certain organs using a reversible, long-term immobilization method.

Green manure plants for remediation of soils polluted by metals and metalloids: ecotoxicity and human bioavailability assessment

Borage, white mustard and phacelia, green manure plants currently used in agriculture to improve soil properties were cultivated for 10 wk on various polluted soils with metal(loid) concentrations representative of urban brownfields or polluted kitchen gardens. Metal(loid) bioavailability and ecotoxicity were measured in relation to soil characteristics before and after treatment. All the plants efficiently grow on the various polluted soils. But borage and mustard only are able to modify the soil characteristics and metal(loid) impact: soil respiration increased while ecotoxicity, bioaccessible lead and total metal(loid) quantities in soils can be decreased respectively by phytostabilization and phytoextraction mechanisms. These two plants could therefore be used for urban polluted soil refunctionalization. However, plant efficiency to improve soil quality strongly depends on soil characteristics.