Effects of cadmium, copper, lead and zinc on growth, reproduction and survival of the earthworm Eisenia fetida (Savigny): Assessing the environmental impact of point-source metal contamination in terrestrial ecosystems

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.

Soil Ecotoxicology Needs Robust Biomarkers: A Meta-Analysis Approach to Test the Robustness of Gene Expression-Based Biomarkers for Measuring Chemical Exposure Effects in Soil Invertebrates

Gene expression-based biomarkers are regularly proposed as rapid, sensitive, and mechanistically informative tools to identify whether soil invertebrates experience adverse effects due to chemical exposure. However, before biomarkers could be deployed within diagnostic studies, systematic evidence of the robustness of such biomarkers to detect effects is needed. In our study, we present an approach for conducting a meta-analysis of the robustness of gene expression-based biomarkers in soil invertebrates. The approach was developed and trialed for two measurements of gene expression commonly proposed as biomarkers in soil ecotoxicology: earthworm metallothionein (MT) gene expression for metals and earthworm heat shock protein 70 (HSP70) gene expression for organic chemicals. We collected 294 unique gene expression data points from the literature and used linear mixed-effect models to assess concentration, exposure duration, and species effects on the quantified response. The meta-analysis showed that the expression of earthworm MT was strongly metal concentration dependent, stable over time and species independent. The metal concentration-dependent response was strongest for cadmium, indicating that this gene is a suitable biomarker for this metal. For copper, no clear concentration-dependent response of MT gene expression in earthworms was found, indicating MT is not a reliable biomarker for this metal. For HSP70, overall marginal up-regulation and lack of a concentration-dependent response indicated that this gene is not suitable as a biomarker for organic pollutant effects in earthworms. The present study demonstrates how meta-analysis can be used to assess the status of biomarkers. We encourage colleagues to apply this open-access approach to other biomarkers, as such quantitative assessment is a prerequisite to ensuring that the suitability and limitations of proposed biomarkers are known and stated. Environ Toxicol Chem 2022;41:2124-2138. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Full life cycle test with Eisenia fetida - copper oxide NM toxicity assessment

Copper oxide nanomaterials (CuONM) are widely used, e.g. as antimicrobial coatings, wood preservatives,fertilizers, etc. Life cycle aspects of Copper Nanomaterials (CuONM) toxicity have been scarcely studied in earthworms, as the focus has been on standard survival and reproduction toxicity tests. Standard tests do not allow for an understanding of which life cycle stage is the most sensitive, and how this can be impacted by CuONMs toxicity to cause longer term population level effects. Since CuONM may release free Cu ions (Cu²⁺) it is relevant to compare CuONM toxicity with CuCl₂ salt. Therefore, the aim of the present study was to assess the effects of CuONM and CuCl₂ throughout the different stages of the full life cycle (FLC) of Eisenia fetida while comparing it with the OECD standard test. Additional endpoints included juvenile survival, growth, maturation, besides survival and reproduction. The FLC test showed that e.g. juvenile survival was especially susceptible during the first 28 days post-hatching, neither juvenile growth nor time to maturity were related to exposure concentration. Both CuONM and CuCl₂ caused a concentration-dependent decrease in population growth, while a hormesis effect was observed at low concentrations of CuCl₂. A reduction in instantaneous growth rate was observed at higher concentrations. The FLC test and the OECD test had different exposure history therefore the ECx values are not comparable across the test systems. Hence, the FLC test enabled the detection of the most vulnerable developmental stages and elucidate different life stage sensitivities between the two Cu exposures.

Interactive effects of metals and carbon nanotubes in a microcosm agrosystem

Agricultural soils are exposed to multiple contaminants through the use of agrochemicals or sewage sludge, introducing metals, nanomaterials and others. Among nanomaterials, carbon nanotubes (CNTs) are known for their large surface area and adsorption capabilities, possibly modifying other element behavior. However, to date, very little is known about the impacts of such interactions in agrosystems. In this study, we aimed at understanding the transfer and toxicity of contaminants (Cd, Pb, Zn and CNTs) in microcosms including native soil bacteria, earthworms and lettuce. After a 6 week exposure, no effect of the addition of CNTs to metal contaminated soils was detected on bacterial concentration or earthworm growth. However, in lettuce, an interactive effect between CNTs and metals was highlighted: in the soil containing the highest metal concentrations the addition of 0.1 mg kg^-1 CNTs led to a biomass loss (-22%) and a flavonoid concentration increase (+27%). In parallel, the addition of CNTs led to differential impacts on elemental uptake in lettuce leaves possibly related to the soil organic matter content. For earthworms, the addition of 10 mg kg^-1 CNTs resulted in an increased body elemental transfer in the soil with the higher organic matter content (Pb: + 34% and Zn: + 25%).

Toxicity and accumulation of lead and cadmium in the land snail, Archachatina papyracea, in a tropical Alfisol from Southwestern Nigeria

Snails are an important link in the transfer of contaminants, especially metals in the food chain. Yet, few studies have examined the toxicity and accumulation of metals in snails in the tropics. This study assessed the toxicity and accumulation of two non-essential metals (cadmium and lead) to the tropical snail Archachatina papyracea. Specimens of the snail A. papyracea were exposed in a loamy soil collected from Ile-Ife, Nigeria and spiked with varying concentrations of Cd and Pb over 28 days. Survival and weight change of snails were monitored weekly, while tissue accumulation was assessed at the end of the 28-day period. Survival was a more sensitive endpoint than the weight change of snails. The Cd median lethal concentration (LC50) value was 93 ± 4.4 mg/kg, while the median effect concentration (EC50) for snail weight change was 131 ± 41 mg/kg. For Pb, LC50 value was 1121 ± 457 mg/kg, while the EC50 value for weight change was higher at 4541 ± 1180 mg/kg. Therefore, Cd was a factor of about 10 to 30 × more toxic than Pb, consistent with findings on the relative toxicity of Cd and Pb to other soil organisms, including earthworms, springtails, and mites. Although not included initially as an endpoint, egg production in the snails decreased with increasing Cd and Pb concentrations in the substrate. Metal analysis of the foot and visceral mass of surviving snails showed progressive accumulation of Cd and Pb as concentration increased, showing the tendency to use body residue of A. papyracea as an indicator of metal pollution. It further suggests the role of this snail species in above-ground metal transfer in the food chain and highlights the potential danger for human consumption.

Impacts of sewage sludges deposition on agricultural soils: Effects upon model soil organisms

During years sewage sludges have been worldwide poured in agricultural soils to enhance vegetal production. The "Landfill 17" located in Gernika-Lumo town (43°19'28.9"N 2°40'30.9"W) received for decades sewage sludges from the local Waste Water Treatment Plant (WWTP) with agricultural purposes. To this WWTP, several pollutants as heavy metals (Cd, Cr, Ni, Pb), PAHs (benzo(a)pyrene among many others) and pesticides (i.e. dieldrin) could have arrived from local industry and be widespread all over the landfill. Soil invertebrates like earthworms and plants are of special interest due to their close contact with the polluted matrix and their potential effects by the presence of pollutants. In this context, the aim of the present work was to determine the health status of landfill soils by evaluating the effects on model soil organisms exerted by long-lasted pollutants after on site deposition of WWTP active sludges. With such a purpose, different standard toxicity tests and cellular level endpoints were performed on lettuce and earthworms. Indeed, germination (EPA 850.4100) and root elongation (EPA 850.4230) tests were carried out in Lactuca sativa, while OECD acute toxicity test (OECD-204), reproduction test (OECD-222) and Calcein-AM viability test with coelomocytes were applied in Eisenia fetida worms. For the exposure, soils collected in the landfield containing low, medium and high concentrations of pollutants were selected, and as reference LUFA 2.3 natural standard soil was chosen. While no differences were shown in the assays with L. sativa, significant differences between sludge exposed groups and control group were recorded with E. fetida, with lower coelomocyte number and viability and higher tissue metal accumulation after 28 days of exposure to polluted soils. These results confirmed the impact of contaminants to soil biota even after long periods of time.

Earthworm Eisenia fetida potential for sewage sludge amended soil valorization by heavy metal remediation and soil quality improvement

Sewage sludge reuse in agriculture is increasing, however it can be an important route for contaminants to enter the environment. The aim of this study was to evaluate earthworm Eisenia fetida capability to reduce heavy metal content in the sewage sludge (SS) amended soil and increase soil fertility in terms of soil nutrients content. Adult earthworms were introduced into aged SS amended soil (0-200 Mg ha^-1) and left for 65 days. Earthworms have stabilized soil pH and accelerated organic matter mineralization. The concentrations of most heavy metals during the vermiremediation sharply decreased, K and Mg decreased to a moderate extent, whereas Ca content has increased. The highest removal efficiency was detected for Ni, Co and Mn (> 80%), bioconcentration factors were as follows Zn > Co > Cu > Ni > Mn > Cr. The content of major nutrients (S, P) was substantially higher compared to the initial values. The most efficient remediation and soil quality improvement was achieved under the doses of 25-50 Mg ha^-1. Higher (≥ 100 Mg ha^-1) doses might restrict this technique application because of earthworm mortality and retarded growth. Overall, the study shows that vermiremediation might be a sustainable technique for ecological stabilization of SS amended soil and converting to usable for agricultural needs.

Assessments of the impact of metals on juvenile earthworms (Eisenia fetida) in laboratory conditions

The aim of this study was to evaluate the impact of different concentrations of copper and zinc on the mortality and bodyweight of juvenile earthworms in artificial soil. Copper was more toxic with complete mortality at the dose rate of 1000 mg/kg. Bodyweight loss of earthworms was observed immediately, after the first week, except at the lowest concentration. In comparison to control, there were significant differences in the bodyweight loss every week in the concentrations of 333 and 666 mg/kg, and also 167 mg/kg in the fourth, sixth, and eighth week. Zinc has not shown a significant effect on mortality, except in the highest concentration, where survival was less than 25%. Statistically significant effect (p < 0.05) on bodyweight was registered only at the highest concentration, every week. The impact of metals on earthworm populations should be more accurately assessed, and data for juvenile earthworms should be considered when proposing a safe concentration of pollutants in the environment, because of the great importance of these animals' presence in the soil.

Lead acetate ecotoxicity in tropical soils

Lead acetate (AcPb) is an important raw material used in chemical industries worldwide. The potential toxicity of AcPb is generally attributed to the presence of Pb. However, the effect of AcPb on the environment as a whole is still poorly known. This study aimed to evaluate AcPb toxicity on three standard species of soil invertebrates and two plant species using ecotoxicology tests. Three tropical soils (Oxisol, Inceptisol, and Tropical Artificial Soil (TAS)) were contaminated with different concentrations of AcPb and one dose of K-acetate (positive control). These soils were used in tests with Eisenia andrei (earthworm), Folsomia candida (springtail), Enchytraeus crypticus (enchytraeid), Zea mays (maize), and Phaseolus vulgaris (common bean). Dose-response curves obtained in the laboratory tests were used to estimate the EC₅₀ values for each species. Among invertebrates, the highest sensitivity to AcPb was observed for E. crypticus in the TAS (EC₅₀ = 29.8 mg AcPb kg^-1), whereas for E. andrei and F. candida the highest sensitivity was observed in the Oxisol (EC₅₀ = 141.9 and 1835 mg AcPb kg^-1, respectively). Folsomia candida was the least sensitive invertebrate species to AcPb in all soils. Among plant species, Z. mays was less sensitive (EC₅₀ = 1527.5 mg AcPb kg^-1) than P. vulgaris (EC₅₀ = 560.5 mg AcPb kg^-1) in the Oxisol. The present study evidenced that the toxicity of AcPb should not be attributed uniquely to the presence of Pb, as the treatment containing uniquely Ac provoked the same toxicity as the highest dose of AcPb.

Bioavailability and Ecotoxicity of Lead in Soil: Implications for Setting Ecological Soil Quality Standards

Ecological soil quality standards for lead (Pb) that account for soil Pb bioavailability have not yet been derived. We derived such standards based on specific studies of the long-term bioavailability and toxicity of Pb to soil organisms and a compilation of field data on the bioaccumulation of Pb in earthworms. Toxicity thresholds of Pb to plants, invertebrates, or microorganisms vary over more than 2 orders of magnitude, and the lowest values overlap with the range in natural Pb background concentrations in soil. Soils freshly spiked with Pb²⁺ salts exhibit higher Pb bioavailability and lower toxic thresholds than long-term aged and leached equivalents. Comparative toxicity tests on leaching and aging effects suggest using a soil Pb threshold that is 4.0 higher, to correct thresholds of freshly spiked soils. Toxicity to plants and earthworms, and microbial N-transformation and bioaccumulation of Pb in earthworms increase with decreasing effective cation exchange capacity (eCEC) of the soil, and models were derived to normalize data for variation of the eCEC among soils. Suggested ecological quality standards for soil expressed as total soil Pb concentration are lower for Pb toxicity to wildlife via secondary poisoning compared with direct Pb toxicity to soil organisms. Standards for both types of receptors vary by factors of approximately 4 depending on soil eCEC. The data and models we have collated can be used for setting ecological soil quality criteria for Pb in different regulatory frameworks. Environ Toxicol Chem 2021;40:1950-1963. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

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

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

Exposure to copper during larval development has intra- and trans-generational influence on fitness in later life

Anthropogenic pollution has a disadvantageous influence on various life-history traits. Although direct effects are well known, potential fitness-related trans-generational costs are less studied. Previously, empirical findings have demonstrated that environmental conditions faced by the parental generation have an effect on the traits expressed by their offspring. Here, to study this conjecture larvae of the common fruit fly (Drosophila melanogaster) were either exposed to a sub-lethal concentration of copper or reared on uncontaminated larval medium. Adult flies were kept under uncontaminated conditions. For the next generation, individuals were mated with their own group and their offspring were either exposed to copper or fed with uncontaminated larval medium. We found that in the parental generation copper exposure reduced fecundity compared with uncontaminated controls. In the progeny, females suffered impaired fecundity only if their larval condition differed from the conditions experienced by their parents. If the progeny was raised under similar conditions than the parental generation, no effect on fecundity was discovered, suggesting acclimatization to the prevailing conditions after short-time copper exposure (two generations). Our results demonstrate that exposure to an environmental stressor like heavy metals causes intra-and trans-generational fitness costs. Further, individuals may be able to acclimatize in prevailing contaminated conditions, but this might in turn debase fitness under uncontaminated conditions. Our findings are consistent with the prediction of the adaptive parental effects hypothesis which states that parents may produce offspring that are more successful under conditions faced by their parents.

Toxicological effects of bituminous coal dust on the earthworm Eisenia fetida (Oligochaeta: Lumbricidae)

The exploitation of coal is an important resource to generate energy worldwide. However, during the processes of coal extraction, transport, and cargo, dust particles are released into the environment. The aim of this study was to determine the toxicological effects of bituminous coal dust (<38 µm), obtained from a sample collected in a coal mine in Colombia, on the annelid Eisenia fetida. The earthworm culture was standardized under laboratory conditions to evaluate mortality, as well as morphological, physiological and histological changes using concentrations varying from 1 to 4% w/w coal dust in artificial soil, after 7, 14, and 28 days of exposure. In addition, an avoidance assay was carried out after 48-h treatment. Histopathological analysis was performed at the end of the experiment. After the sub-chronic exposure, an increase in mortality was observed at the highest coal dust concentration compared to the untreated group. Alterations in morphology and physiology of the exposed annelids were mostly evidenced at the greatest tested concentrations (3-4%) and exposure times (≥14 days). Changes included loss of weight and color, abundant mucus production, constriction, peeling of the epidermis, clitellum involution, violent movements and lethargy. Avoidance of coal dust-polluted soil followed a concentration-response relationship. Histopathological findings revealed changes on the cuticle, as well as in the circular and longitudinal muscle layers in animals living in soils containing 3 and 4% coal particles. In short, E. fetida exposed to coal dust experienced several pathological changes, suggesting that this pollutant may induce population problems in macroinvertebrates present in coal mining areas.

Responses of soil and earthworm gut bacterial communities to heavy metal contamination

The large accumulation of heavy metals in the soil surrounding steel factories has become a severe environmental problem. However, few studies have focused on how the earthworm gut microbiota responds to heavy metals in the soil. This study used research sites at a steel factory in Nanjing, China, to investigate how the soil bacterial community and earthworm gut microbiota respond differently to heavy metal contamination using Illumina high-throughput sequencing targeting 16S rRNA genes. The bacterial community of earthworm guts showed a distinct structure compared with that of the soil, featuring a higher relative abundance of Proteobacteria (45.7%) and Bacteroidetes (18.8%). The bacterial community in the earthworm gut appeared more susceptible to heavy metal contamination compared with the soil community. For example, we identified 38 OTUs (Operational taxonomic units) significantly influenced by contamination among 186 abundant OTUs in the soil, whereas 63 out of the 127 abundant OTUs in the earthworm gut were altered significantly under contamination. This susceptibility may be partly explained by the lower alpha diversity and distinct microbial interactions in the gut. In addition, the accumulation of heavy metals also stimulated the growth of potential plant growth promoting bacteria (PGPB) in the earthworm gut, especially those related to indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylic acid deaminase (ACCD) production, which may potentially benefit the phyto-remediation of heavy metals. These results contribute to our understanding of the soil biota and its interactions under heavy metal contamination and may provide further insights into the phyto-remediation of metal-contaminated soil.

Consequences of surface coatings and soil ageing on the toxicity of cadmium telluride quantum dots to the earthworm Eisenia fetida

The bioaccumulation potential and toxic effects of engineered nanomaterials (ENMs) to earthworms are poorly understood. Two studies were conducted following OECD TG 222 on Eisenia fetida to assess the effects of CdTe QDs with different coatings and soil ageing respectively. Earthworms were exposed to carboxylate (COOH), ammonium (NH₄⁺), or polyethylene glycol (PEG) coated CdTe QDs, or a micron scale (bulk) CdTe material, at nominal concentrations of 50, 500 and 2000 mg CdTe QD kg^-1 dry weight (dw) for 28 days in Lufa 2.2 soil. In the fresh soil study, earthworms accumulated similar amounts of Cd and Te in the CdTe-bulk exposures, while the accumulation of Cd was higher than Te during the exposures to CdTe QDs. However, neither the total Cd, nor Te concentrations in the earthworms, were easily explained by the extractable metal fractions in the soil or particle dissolution. There were no effects on survival, but some retardation of growth was observed at the higher doses. Inhibition of Na^+_/K⁺-ATPase activity with disturbances to tissue electrolytes, as well as tissue Cu and Mn were observed, but without depletion of total glutathione in the fresh soil experiment. Additionally, juvenile production was the most sensitive endpoint, with estimated nominal EC₅₀ of values >2000, 108, 65, 96 mg CdTe kg^-1 for bulk, PEG-, COOH- and NH₄⁺-coated CdTe QDs, respectively. In the aged soil study, the accumulation of Cd and Te was higher than in the fresh soil study in all CdTe QD exposures. Survival of the adult worms was reduced in the top CdTe-COOH and -NH₄⁺ QD exposures by 55 ± 5 and 60 ± 25%, respectively; and with decreases in growth. The nominal EC₅₀ values for juvenile production in the aged soil were 165, 88, 78 and 63 mg CdTe kg^-1 for bulk, PEG-, COOH- and NH₄⁺-coated CdTe QDs, respectively. In conclusion, exposure to nanoscale CdTe QDs, regardless of coating, caused more severe toxic effects that the CdTe bulk material and the toxicity increased after soil ageing. There were some coating-mediated effects, likely due to differences in the metal content and behaviour of the materials.

The use of an Allonais inaequalis reproduction test as an ecotoxicological bioassay

Ecotoxicological bioassays have been widely utilized to evaluate the toxicity of substances to organisms. However, the main challenge for researchers is finding native species to assess the effects of pollutants on aquatic biota. The tropical Oligochaeta, Allonais inaequalis, can be used as a test organism in bioassays to understand the effects of toxicants on aquatic ecosystems and their impact on native aquatic biota. In this study, we tested four methodological designs to validate the use of our "Allonais inaequalis reproduction test" as an ecotoxicological bioassay. For each sample, the assay consisted of a bottle containing 10 mg of sterilized fine sand, 60 mL of dechlorinated tap water and 6 organisms, fed at the beginning of the test and again after 5 days. The assay was first established in a controlled environment and then used to evaluate a stressed environment containing one of the following three toxicants suggested by the OECD (2008) and Corbi et al. (2015): zinc chloride, copper sulfate, or potassium chloride. Our results showed that the best experimental design for reproduction analysis was a static, long-term bioassay, which lasted 10 days without aeration and allowed for the reproduction of multiple generations (10 ± 5 new organisms). The observed inhibition reproduction by toxicants (EC50 ranging between 0.2 mg L^-1 and 1.36 g L^-1) validated the methods used in this paper. The use of a reproduction endpoint is a new contribution to the ecotoxicological toolbox, examining responses from a native organism to predict the effects of pollutants in an aquatic environment.

Increasing level of liquid pig manure reduces Eisenia andrei and Enchytraeus crypticus reproduction in subtropical soils

Wastes generated in pig production are widely used as agricultural fertilizers. Nevertheless, such form of disposal supplies large amounts of waste in soils annually and can cause environmental pollution. The ecological risk of this practice to soil organisms has received little attention. Ecotoxicological tests are used to evaluate the toxicity of contaminants added to the soil biota. The aimed to evaluate the effect of liquid pig manure (LPM) on the reproduction of Eisenia andrei and Enchytraeus crypticus when applied in natural soils. LPM doses caused effects on earthworm reproduction in both soils, with EC₅₀ of 112 and 150 m³ ha⁻¹ in the Entisol and Nitosol, respectively. On enchytraeids, LPM had bigger effects, leading to EC₅₀ of 17.7 and 45.0 m³ ha⁻¹ in the Entisol and Nitosol, respectively. The results emphasize the importance to consider the ecological risks of LPM of conducting studies with natural soils and edaphic fauna as indicators.

Impacts of metallic trace elements on an earthworm community in an urban wasteland: Emphasis on the bioaccumulation and genetic characteristics in Lumbricus castaneus

Metallic trace elements (MTEs) soil pollution has become a worldwide concern, particularly regarding its impact on earthworms. Earthworms, which constitute the dominant taxon of soil macrofauna in temperate regions and are crucial ecosystem engineers, are in direct contact with MTEs. The impacts of MTE exposure on earthworms, however, vary by species, with some able to cope with high levels of contamination. We combined different approaches to study the effects of MTEs at different levels of biological organisation of an earthworm community, in a contaminated urban wasteland. Our work is based on field collection of soil and earthworm samples, with a total of 891 adult earthworms from 8 species collected, over 87 quadrats across the study plot. We found that MTE concentrations are highly structured at the plot scale and that some elements, such as Pb, Zn, and Cu, are highly correlated. Comparing species assemblage to MTE concentrations, we found that the juvenile and adult abundances, and community composition, were significantly affected by pollution. Along the pollution gradient, as species richness decreased, Lumbricus castaneus became more dominant. We thus investigated the physiological response of this species to a set of specific elements (Pb, Zn, Cu, and Cd) and studied the impacts of MTE concentrations at the plot scale on its population genetic. These analyses revealed that L. castaneus is able to bioaccumulate high quantities of Cd and Zn, but not of Cu and Pb. The population genetic analysis, based on the genotyping of 175 individuals using 8 microsatellite markers, provided no evidence of the role of the heterogeneity in MTE concentrations as a barrier to gene flow. The multidisciplinary approach we used enabled us to reveal the comparatively high tolerance of L. castaneus to MTE concentrations, suggesting that this is a promising model to study the molecular bases of MTE tolerance.

Effects of elevated temperatures and cadmium exposure on stress biomarkers at different biological complexity levels in Eisenia fetida earthworms

Several ecotoxicological studies assessed metal toxicity upon soil biota and other communities but were mainly focused on the study of a single chemical and usually under optimal conditions of temperature. Meanwhile an increasing global warming is leading to new scenarios by combining different stress factors; chemical stress and thermal stress. Presently, this study aims to assess the joint effects produced by cadmium and elevated temperature on earthworms different levels of biological complexity. Eisenia fetida earthworms were maintained at 19 °C and 26 °C and simultaneously exposed to four Cd concentrations (1.25, 2.5, 25 and 125 mg Cd/Kg soil) for 14 (Short term exposure) and 56 days (reproduction test). Endpoints were addressed at different levels of biological complexity: reproductive impairment (cocoons and juvenile productions), Cd tissue accumulation, mortality of adults, weight loss and cytotoxic effects (coelomocyte viability). In the Short term exposure, increase in temperature produced a larger accumulation of Cd. Hence, earthworms exposed to 125 mg Cd/kg soil under heat stress (26 °C) showed a two fold higher Cd accumulation comparing to those at 19 °C. Earthworms exposed to moderate-high concentrations of Cd (2.5-125 mg Cd/kg) and maintained at 26 °C showed severe weight loss and high mortality rates. The neutral red uptake capacity of coelomocytes extruded from earthworms exposed to the highest Cd concentration decreased after 14 d at 19 °C, and more markedly at 26 °C. The reproduction impairment (decreased number of cocoons) was enhanced after exposure to concentrations higher than 2.5 mg Cd/kg at 26 °C, and after exposure to 125 mg Cd/kg at 19 °C. Earthworm reproduction capability is highly vulnerable to the effect of toxicants at elevated temperatures and sublethal concentrations.

Uptake, toxicity, and maternal transfer of cadmium in the oribatid soil mite, Oppia nitens: Implication in the risk assessment of cadmium to soil invertebrates

Cadmium (Cd) is a heavy metal of concern in contaminated sites because of its high toxicity to soil biota and humans. Typically, Cd exposure is thought to be dominated by dissolved Cd in soil pore water and, thus, dermal uptake. In this study, we investigated the uptake, toxicity, and maternal transfer of Cd in a standard soil invertebrate, the oribatid mite (Oppia nitens), which is common to boreal and temperate ecozones. We found total soil Cd predicted Cd uptake in adult and juvenile O. nitens with no significant uptake from pore water by juvenile mites. Cadmium significantly inhibited juvenile production and recruitment as well as reduced adult fecundity. Adult O. nitens maternally transferred 39-52% of their Cd body burden to juveniles (tritonymphs) while the maternally-acquired Cd accounted for 41% of the juvenile internal Cd load. Our results suggest that dermal adsorption of metal ions is not important for O. nitens and that maternal transfer of Cd in soil invertebrates has ecological and toxicological implications for populations of soil invertebrates. Maternal transfer should be incorporated as a criterion in setting environmental soil quality guidelines (SQG_E) for cadmium and other non-essential heavy metals.

Interaction effects of salinity, sewage sludge, and earthworms on the fractionations of Zn and Cu, and the metals uptake by the earthworms in a Zn- and Cu-contaminated calcareous soil

This study assessed the effects of salinity and sewage sludge on the fractionation of Zn and Cu in a soil around a lead-zinc mine as well as their uptake by earthworms (Eisenia fetida) in order to identify novel methods for employing the earthworms in waste management techniques. Eisenia fetida specimens were kept under laboratory conditions for 42 days. The first treatment involved the addition of 0%, 2%, 4%, and 8% (w/w) sewage sludge to contaminated soil. In the second treatment, NaCl was added to the soil at concentrations of 0, 1170, 2340, 3510, and 4680 mg L^-1. The results indicated that the combined application of high salinity and sewage sludge had adverse effects on the survival of the earthworms. The presence of the earthworms increased the amount of Zn and Cu bound to organic matter. The organic fraction of Zn and Cu also significantly aggregated with increasing salinity levels. The interaction of salinity and earthworm showed that the residual Cu fraction increased with the presence of earthworm and decreased with increasing salinity. The residual fraction of Cu was significantly affected by the interactions of salinity and sewage sludge, where the highest amount was seen in the EC₀ (distilled water) × SS₈ (8% sewage sludge) treatment. The Zn and Cu contents increased with the earthworms when exposed to higher levels of salinity and sewage sludge.

Learning from the past and considering the future of chemicals in the environment

Knowledge of the hazards and associated risks from chemicals discharged to the environment has grown considerably over the past 40 years. This improving awareness stems from advances in our ability to measure chemicals at low environmental concentrations, recognition of a range of effects on organisms, and a worldwide growth in expertise. Environmental scientists and companies have learned from the experiences of the past; in theory, the next generation of chemicals will cause less acute toxicity and be less environmentally persistent and bioaccumulative. However, researchers still struggle to establish whether the nonlethal effects associated with some modern chemicals and substances will have serious consequences for wildlife. Obtaining the resources to address issues associated with chemicals in the environment remains a challenge.

Subcellular partitioning of cadmium and lead in Eisenia fetida and their effects to sperm count, morphology and apoptosis

Earthworms and their biomarkers are considered good indicators for assessing the effects of toxic chemicals. Therefore, in this study, we exposed Eisenia fetida to lethal and sub-lethal concentrations of Cd and Pb nitrate in artificial soil for 14 and 28 days to evaluate the impact on subcellular partitioning, lethal toxicity (LC₅₀), growth, sperm count, morphology and apoptosis (using TUNEL assay). The soluble internal pools of both metals were good predictors of the responses of biomarkers. We found sperm deformation, TUNEL positive sperms and weight loss positively and sperm count negatively correlated with the concentrations of Cd and Pb in the total internal and cytosolic fraction (p < 0.01) and to a lesser extent with Pb concentrations in the granular fraction (p < 0.05). Fourteen days LC₅₀ for Cd and Pb were 2169 ± 322 and 6387 ± 904 μg/g, respectively. Cadmium and Pb caused a significant depression in sperm count after 14 (Cd: up to 46.9%; Pb: up to 36.24%) and 28 (Cd: up to 72.47%; Pb: up to 43.12%) days of exposure relative to the control (p < 0.05). Cadmium induced higher abnormality in sperm heads than Pb. For both metals, TUNEL positive sperms significantly increased after 14 (Cd: up to 14.17%; Pb: up to 16.33%) and 28 (Cd: up to 16.33%; Pb: up to 11.67%) days of exposure compared with the control (p < 0.05). The findings of this study, illustrate the importance of considering sperm parameters as a rapid, easy and sensitive biomarker for the evaluation of metal toxicity.

Quality standards for urban waste composts: The need for biological effect data

The recently approved European Union (EU) Circular Economy Package intends to boost the production of fertilizing products, such as composts obtained from urban wastes (UWC) and the harmonization of their quality standards (certification), to avoid market rejection. UWC quality assessment frameworks in Europe, including the Portuguese and EU latest proposal on regulation of UWC production/commercialization are mostly based on physical-chemical and agronomical characterization. These do not provide any insight on the fraction of contaminant/mixture of contaminants bioavailable for non-target organisms, nor the existence of potential antagonistic and/or synergistic effects on them. The main objective of the present work if to evaluate the effects of UWC application on crop soils using seven standard ecotoxicological tests. Five UWC, two derived from source-separated organic wastes and three from mixed urban wastes were selected and tested using a battery of ISO guideline assays with plants and soil invertebrates. The tested doses intended to simulate over-use and repeated application scenarios, common practices among farmers. The results showed that the highest toxicity was observed for the UWC originated from source-separated organic wastes, when using concentrations slightly above the maximum annual doses. Excepting for this UWC, all the derived NOEC (No Observed Effect Concentration) were equal or higher than the maximum annual doses. The UWC toxicity for the tested species increased as follows: T. aestivum < L. sativa < E. crypticus < F. candida < E. andrei. UWC salinity, rather than the content of potentially toxic elements (PTEs), could explain the negative effects observed, considering that the composts are all equally stabilized. These results reinforce the need to include data from biological susceptibility of the receptors at risk on the existing regulation, to obtain a more realistic view of the potential risks and to adapt the UWC application practices, ultimately boosting the confidence of target-consumers.

Can Local Enhancement in Earthworms Affect the Outcome of the Standard Earthworm Avoidance Test?

Earthworms exhibit clumping behaviour in and out of the soil. However, it remains unknown if such social behaviour ultimately influences the outcome of ecotoxicological experiments in the laboratory. We performed several overnight avoidance tests to determine whether social behaviour (i.e., local enhancement) is a factor in pollution avoidance behaviour in the earthworm Eisenia fetida. The results showed that there was no clear influence of social behaviour on the choice or avoidance of Cd contaminated soils, although we suspect that 50 mg Cd/kg might not have been high enough to elicit a significant avoidance response. Nevertheless, when offered a choice between clean undisturbed soil and previously inhabited soil, the worms preferred the previously inhabited soil (p < 0.01). While the level of metal pollution investigated in this study did not disrupt or help predict social dynamics, local enhancement, perhaps driven by some sort of habitat imprinting, was successfully documented in Eisenia fetida.

Oppia nitens C.L. Koch, 1836 (Acari: Oribatida): Current Status of Its Bionomics and Relevance as a Model Invertebrate in Soil Ecotoxicology

The oribatid soil mite Oppia nitens C.L. Koch, 1836, is a model microarthropod in soil ecotoxicity testing. This species has a significant role in supporting soil functions and as a suitable indicator of soil contamination. Despite its significance to the environment and to ecotoxicology, however, very little is known of its biology, ecology, and suborganismal responses to contaminants in the soil. In the present review, we present detailed and critical insights into the biology and ecology of O. nitens in relation to traits that are crucial to its adaptive responses to contaminants in soil. We used a species sensitivity distribution model to rank the species sensitivity to heavy metals (cadmium and zinc) and neonicotinoids (imidacloprid and thiacloprid) compared with other standardized soil invertebrates. Although the International Organization for Standardization and Environment and Climate Change Canada are currently standardizing a protocol for the use of O. nitens in soil toxicity testing, we believe that O. nitens is limited as a model soil invertebrate until the molecular pathways associated with its response to contaminants are better understood. These pathways can only be elucidated with information from the mites' genome or transcriptome, which is currently lacking. Despite this limitation, we propose a possible molecular pathway to metal tolerance and a putative adverse outcome pathway to heavy metal toxicity in O. nitens. Environ Toxicol Chem 2019;38:2593-2613. © 2019 SETAC.

Ecotoxicity of a new biopesticide produced by Lavandula luisieri on non-target soil organisms from different trophic levels

Plant-based biopesticides have become an eco-friendly alternative to synthetic pesticides by reducing the undesired environmental impacts and side-effects on human health. However, their effects on the environment and especially on non-target organisms have been little studied. This study analyses the ecotoxicological effects of the extract of Lavandula luisieri on soil non-target organisms from different trophic levels: the earthworm Eisenia fetida, the plant Allium cepa and a natural-soil microbial community whose taxonomy was analysed through 16S rRNA gene sequencing. The extract tested is the hydrolate -product from a semi industrial steam distillation process- of a Spanish pre-domesticated variety of L. luisieri. This hydrolate has been recently shown to have bionematicide activity against the root-knot nematode Meloidogyne javanica. A previous study showed that the main components of the hydrolate are camphor and 2,3,4,4-Tetramethyl-5-methylidenecyclopent-2-en-1-one. Hydrolate caused acute toxicity (LC₅₀ 2.2% v/v) on A. cepa, while only a slight toxicity on E. fetida (LC₅₀ > 0.4 mL/g). All the concentrations tested (from 1 to 100% v/v) caused a significant decrease in bacterial growth (LC₅₀ 9.8% v/v after 120 h of exposure). The physiological diversity of the community was also significantly altered, except in the case of the lowest concentration of hydrolate (1% v/v). The ability of soil microbial communities to use a variety of carbon sources increased for all substrates at the highest concentrations. These results show that both the plants and bacterial communities of the soil can be affected by the application of biopesticides based on these hydrolates, which highlights the need for a more detailed risk assessment during the development of plant-based products.

Caenorhabditis elegans as a tool for environmental risk assessment: emerging and promising applications for a "nobelized worm"

Caenorhabditis elegans has been an invaluable model organism in research fields such as developmental biology and neurobiology. Neurotoxicity is one of the subfields greatly profiting from the C. elegans model within biomedical context, while the corresponding potential of the organism applied to environmental studies is relevant but has been largely underexplored. Within the biomedical scope, the implication of metals and organic chemicals with pesticide activity (hereinafter designated as pesticides) in the etiology of several neurodegenerative diseases has been extensively investigated using this nematode as a primary model organism. Additionally, as a well-known experimental model bearing high sensitivity to different contaminants and representing important functional levels in soil and aquatic ecosystems, C. elegans has high potential to be extensively integrated within Environmental Risk Assessment (ERA) routines. In spite of the recognition of some regulatory agencies, this actual step has yet to be made. The purpose of this review is to discuss the major advantages supporting the inclusion of C. elegans in lower tiers of ERA. Special emphasis was given to its sensitivity to metals and pesticides, which is similar to that of other model organisms commonly used in ERA (e.g. Daphnia magna and Eisenia sp.), and to the large array of endpoints that can be tested with the species, both concerning the aquatic and the soil compartments. The inclusion of C. elegans testing may hence represent a relevant advance in ERA, providing ecologically relevant insights toward improvement of the regulatory capacity for establishing appropriate environmental protection benchmarks.

The Comparative Effects of Metals on the Hatching of Earthworm Cocoons

To establish the use of Metaphire posthuma as a sensitive model for ecotoxicological studies, the comparative effects of five metals on the hatching profiles of the cocoons of the earthworms, Metaphire posthuma, Eisenia foetida and Perionyx excavatus, were studied. The cocoons of the three species of earthworms were exposed to copper, chromium (III), chromium (VI), lead and zinc at 1.25, 2.5, 5.0 and 10.0 ppm. Viable cocoons were incubated at 20 +/- degrees C by using the immersion method. The results indicated that the inhibition of cocoon hatching was concentration dependent. The normal hatching, delayed hatching and non-viability of cocoons were recorded. At a concentration of 1.25 ppm, there was almost no effect on the hatching of the cocoons of all three species of earthworms, except when exposed to chromium (VI), but higher concentrations (2.5 and 5.0 ppm) caused severe effects. It was concluded that M. posthuma was more sensitive than the other two species, and that it is a suitable model for use in ecotoxicity testing.

Protecting vulnerable individuals in a population: is the avoidance response of juvenile soil invertebrates more sensitive than the adults response?

Juveniles are generally considered more sensitive to contaminants than adults. However, it is unknown if the behavioral responses of juvenile soil invertebrates is different than the adults. The absence of juvenile or adult soil invertebrates in contaminated soils due to avoidance adversely impacts the soil quality. Here, we assessed the avoidance response in two life stages (juvenile and adult) of three standardized soil toxicity test invertebrates (Folsomia candida, Enchytraeus crypticus and Eisenia fetida) exposed to phenanthrene, copper and sodium chloride contaminated soil. Interestingly, we found the juvenile's avoidance response could be more sensitive, less sensitive and the same as the adult's avoidance response, depending on the contaminant and test species. The juvenile avoidance response of E. fetida to sodium chloride, and E. crypticus and E. fetida to copper was more sensitive than the adult's response. In contrast, the avoidance response of juvenile F. candida to sodium chloride was less sensitive than the adult's response. No life stage differences were observed in the avoidance response of E. crypticus individuals exposed to sodium chloride, F. candida individuals exposed to copper and E. fetida individuals exposed to phenanthrene. Although life stage differences in avoidance responses were evident for some species and contaminants, it was not consistent. In terms of avoidance, the assumptions that juveniles are the most sensitive individuals in a population is not always true.

Assessment of the stabilization of heavy metal contaminants in soils using chemical leaching and an earthworm bioassay

Soil stabilization is a remedial technique that reduces the exposure of the soil environment to soil contaminants. Its efficacy can be assessed by determining whether the environmental availability of a contaminant decreases following treatment. We evaluated several chemical leaching treatments by assessing both contaminant leachability and bioaccumulation in the earthworm Eisenia fetida, and determined the most effective treatment for achieving soil stabilization. Soil samples contaminated with As, Cd, Cu, Pb, and/or Zn were collected from abandoned mine areas and stabilized by adding limestone and steel slag (5% and 2% w/w, respectively). All leaching and earthworm tests were conducted using both contaminated and stabilized soils. In addition to bioaccumulation in earthworms, several toxicity parameters (number of cocoons, growth changes, and survival rates) were also assessed to determine the effects of the treatments on the earthworms. The study showed that treatment of soil with EDTA-NH₄OAc resulted in a significant decrease in contaminant leachability following soil stabilization. There was an increase in survival and growth of earthworms exposed to the stabilized soil compared with those exposed to the non-stabilized soil. Bioaccumulation in earthworms was found to be statistically correlated with the leachability of As by EDTA-NH₄OAc. We conclude that limestone and steel slag effectively decreased the availability of heavy metals in the soil and reduced the toxicity to earthworms. Leaching with EDTA-NH₄OAc has the potential to be predictive in estimating the bioavailability of As in soils, but further studies are needed if it is to be proposed as a standard method.

Disentangling the effects of the aqueous matrix on the potential toxicity of liquid pig manure in sub-tropical soils under semi-field conditions

Inadequate application of liquid pig manure (LPM) may pose risks to the soil due to the potential contaminants that exists, as well as by the large water input that can originate excessive moisture. By using Terrestrial Model Ecosystems, this study aimed to evaluate the effect of application of LPM (82% moisture) using the application rates of 20, 50 and 150 m³ ha^-1 and also of the corresponding amount of water to understand the origin of effects on the soil fauna of two sub-tropical soils. In general, the results obtained for the two soil types indicated that LPM (150 m³ ha^-1) changed the composition of soil fauna, with an increase in the abundance of insect larvae and dipterans, but a decrease in the number of earthworms and enchytraeids. Microbial biomass, soil respiration and the nutrients Mg, K and P increased with the amount of LPM supplied to the soil. When analysing the effects of adding large volumes of water via the LPM, results showed that application did not originate significant effects on the parameters measured. The differences obtained when comparing both treatments were mainly attributed to the organic load brought by the LPM and not to the amount of water without LPM.

Copper accumulation and toxicity in earthworms exposed to CuO nanomaterials: Effects of particle coating and soil ageing

Engineered nanomaterials (ENMs) may be functionalised with a surface coating to enhance their properties, but the ecotoxicity of the coatings and how hazard changes with ageing in soil is poorly understood. This study determined the toxic effect of CuO ENMs with different chemical coatings on the earthworm (Eisenia fetida) in fresh soil, and then after one year in aged soil. In both experiments, earthworms were exposed for 14 days to the CuO materials at nominal concentrations of 200 and 1000 mg Cu kg^-1 dry weight and compared to CuSO₄. In the fresh soil experiment, CuO-COOH was found to be the most acutely toxic of the nanomaterials (survival, 20 ± 50%), with tenfold increase of total Cu in the earthworms compared to controls. Sodium pump activity was reduced in most CuO ENM treatments, although not in the CuSO₄ control. There was no evidence of glutathione depletion or the induction of superoxide dismutase (SOD) activity in any treatment. Histology showed a mild hypoplasia of mucous cells in the epidermis with some nanomaterials. In the aged soil, the CuO-NH₄⁺ was the most acutely toxic ENM (survival 45 ± 3%) and Cu accumulation was lower in the earthworms than in the fresh soil study. Depletion of tissue Mn and Zn concentrations were seen in earthworms in aged soil, while no significant effects on sodium pump or total glutathione were observed. Overall, the study showed some coating-dependent differences in ENM toxicity to earthworms which also changed after a year of ageing the soil.

The role of CuZn- and Mn-superoxide dismutases in earthworm Eisenia andrei kept in two distinct field-contaminated soils

Polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), together with polycyclic aromatic hydrocarbons (PAHs), represent highly toxic and persistent organic environmental pollutants, especially due to their capability for bioaccumulation in fatty tissues. To observe the environmentally relevant effect of these compounds on earthworms, two soils naturally contaminated with PCDD/Fs and PAHs were used in our experiments. We focused on the role of CuZn- and Mn-superoxide dismutases. We assembled a full-length sequences of these molecules from Eisenia andrei earthworm and confirmed their activity. We demonstrated the significant reduction of CuZn-SOD on both mRNA and enzyme activity levels and increased levels of reactive oxygen species in earthworms kept in PCDD/F-polluted soil, which corresponds to the observed histopathologies of the earthworm intestinal wall and adjacent chloragogenous tissue. The results show an important role of CuZn-SOD in earthworm tissue damage caused by PCDD/Fs present in soil. We did not detect any significant changes in the mRNA expression or activity of Mn-SOD in these earthworms. In earthworms maintained in PAH-polluted soil the activity of both CuZn-SOD and Mn-SOD significantly increased. No histopathological changes were detected in these worms, however significant decrease of coelomocyte viability was observed. This reduced viability was most likely independent of oxidative stress.

The reproductive responses of earthworms (Eisenia fetida) exposed to nanoscale zero-valent iron (nZVI) in the presence of decabromodiphenyl ether (BDE209)

Reproductive toxicity of nanoscale zero-valent iron (nZVI) along with coexisting decabromodiphenyl ether (BDE209) to earthworm Eisenia fetida (E. fetida) remains unknown. In the present study, the reproductive responses of E. fetida exposed to 100, 500 and 1000 mg kg^-1 of nZVI showed a significant (P < 0.05) decline up to 35.6%, 60.0% and 93.3%, respectively, compared to the controls. Expression levels of annetocin (ANN) gene indicated a remarkable (P < 0.05) down-regulation (59.2%, 58.2% and 95.0%, correspondingly), and it was positively correlated with reproductive rates (R = 0.94). Iron contents in E. fetida were also relevant to reproductive behavior (R = 0.84) and ANN expression (R = 0.75). Additionally, seminal vesicles displayed a progressive degeneration with increasing nZVI levels. The addition of BDE209 to low level of nZVI-polluted group (100 mg kg^-1 dw) barely caused clear changes on reproduction, histopathology and ANN, while the coexistence resulted in significant impacts in comparison with high level of single nZVI exposure (1000 mg kg^-1 dw). These observations would provide some significant information concerning joint toxicity of the two chemicals in a soil system.

Ecological risk evaluation of combined pollution of herbicide siduron and heavy metals in soils

Combined pollution of agrichemicals and heavy metals in urban lawn soils were commonly observed throughout the world, and the co-existed two chemicals could interact with each other both in environment behavior and toxic effect. However, little has been reported on the ecological risk of their combined pollution, especially in field due to lack of systematic methodology. In this study, four soils (C, N1, N2, N3) from two public parks in Beijing, China, with similar properties but contrasting heavy metal contaminated level were chosen to assess the ecological risks of co-existed herbicide siduron and heavy metals. Environmental behaviors of siduron in studied soils were investigated with batch experiments in lab, based on which the environmental exposure level of siduron was simulated with HYDRUS-1D. Results suggested that soil organic matter (SOM) rather than the co-existed heavy metals was the dominant factor affecting the fate and the accumulation of siduron in soils. Soil N2 with the highest SOM, showed the strongest tendency to retain siduron among the studied soils. Significant joint effect of siduron and heavy metals on cucumber root elongation was observed through lab experiments. Thus, the joint toxicity of siduron and heavy metals were calculated based on single toxicology data of them using independent action (IA) and concentration addition (CA) model. Then, the predicted no effect concentration (PNEC_soil) of siduron was calculated with equilibrium partitioning method and extrapolation techniques. The PNEC_soil of siduron was the lowest in heaviest heavy metal contaminated soil N3. The risk characterization ratios (RCR) of siduron in four soils were all >1. The highest RCR of siduron in soil N3 suggested that it was the joint toxicity of siduron and heavy metals to organisms determining the ecological risks of siduron in combined polluted soils.

Effects of soot by-product from the synthesis of engineered metallofullerene nanomaterials on terrestrial invertebrates

The synthesis of carbon-based nanomaterials is often inefficient, generating large amounts of soot with metals as waste by-product. Currently, there are no specific regulations for disposal of engineered nanomaterials or the waste by-products resulting from their synthesis, so it is presumed that by-products are disposed of in the same way as the parent (bulk) materials. We studied the terrestrial toxicity of soot from gadolinium metallofullerene nanomanufacturing on earthworms (Eisenia fetida) and isopods (Porcellio scaber). The metallofullerene soot consisted of carbon particle agglomerates in the nanometer and submicrometer ranges (1-100 and 101-999 nm, respectively), with metals used during nanomanufacturing detectable on the particles. Despite high metal concentrations (>100 000 mg/kg) in the soot, only a relatively small amount of metals leached out of a spiked field soil, suggesting only moderate mobility. Seven- and 14-d exposures in field soil demonstrated that the soot was only toxic to earthworms at high concentrations (>10 000 mg/kg); however, earthworms avoided spiked soils at lower concentrations (as low as 500 mg/kg) and at lower soil pH. The presence of soot in food and soil did not cause isopod avoidance. These data demonstrate that metallofullerene soot from nanomanufacturing may only be toxic to earthworms at high concentrations representative of improper disposal or accidental spills. However, our results indicate that terrestrial invertebrates may avoid soils contaminated with soot at sublethal concentrations. Environ Toxicol Chem 2018;9999:1-12. Published 2018 Wiley Periodicals, Inc. on behalf of SETAC. This article is a US government work, and as such, is in the public domain in the United States of America.

Ecotoxicological effects of binary mixtures of siduron and Cd on mRNA expression in the earthworm Eisenia fetida

This study aimed to investigate the eco-toxicological responses of earthworm (Eisenia fetida) exposed to combined siduron (herbicide) and cadmium (Cd). Eisenia fetida gene expressions including metallothionein (MT) and heat shock protein70 (Hsp70) were analyzed using real-time Polymerase Chain Reaction after individual and combined siduron (0.90, 1.80, 3.60 and 7.20μgcm^-2) and Cd (0.225, 0.45, 0.90 and 1.80μgcm^-2) sublethal exposures. Where, the nature of the toxicological interactions between siduron and Cd in inducing or suppressing MT and Hsp70 expression was determined by applying the Combination index (CI)-isobologram model. The results revealed significant variations in MT and weak changes in Hsp70 expression when the earthworms were exposed to individual Cd. The individual siduron exposure exhibited a significant down-regulation (p<0.01) in MT during all treatments and in Hsp70 expression only at 7.20μgcm^-2 concentration; while the mixtures of siduron and Cd exposures resulted a significant down regulation (p<0.05) in both MT and Hsp70 expressions. Moreover, the combined siduron and Cd exposure revealed nearly additive effect (CI=1) at the lower effect levels and significant synergistic effect (CI<1) at the higher effect levels for both MT and Hsp70 expression. The synergistic effects of combined siduron and Cd suggest that there might be a potential risk connected to the co-occurrence of these chemicals in the environment.

Protective role of metallothionein during regeneration in Eisenia andrei exposed to cadmium

Lumbricid earthworms are often exposed to simultaneous action of various environmental stressors like soil contamination, temperature fluctuation or predators' attacks, which may induce extrusion of coelomocyte-containing coelomic fluid or loss of tail segments. If the injuries are not lethal, renewal of the immune-competent cells and soluble components of coelomic fluid and/or the regeneration of tail segments occurs. The aim of our investigations was to test the hypothesis that exposure of adult earthworms Eisenia andrei to cadmium-polluted soil at room temperature (RT) and/or low temperature (6°C) have adverse effects on restoration of experimentally depleted coelomocytes or on regeneration of amputated posterior segments. Intact control earthworms and their experimental counterparts subjected to electrostimulation-induced coelomocyte depletion or surgical amputation of posterior segments were maintained either in control soil or in soil spiked with cadmium chloride (500mg/kg air-dried soil) at RT or 6°C. Four weeks after the beginning of experiments, cadmium accumulation in earthworm bodies was significantly lower at 6°C than at room temperature. The numbers of restored cells and fluorophore contents were hardly affected by temperature or cadmium. However, cocoon production was reduced by cadmium and completely abolished at 6°C and regeneration of amputated posterior segments was inhibited in cold but was enhanced by cadmium exposure at RT. Independently on the temperature, the 4-week cadmium exposure of adult earthworms was connected with significantly upregulated expression of Cd-metallothionein (but not of catalase, lysenin and phytochelatin) in coelomocytes.

Metabolic Responses of Eisenia Fetida to Individual Pb and Cd Contamination in Two Types of Soils

To characterize the potential toxicity of low Pb- and Cd-contaminated arable soils, earthworms were exposed to Pb contaminated ferrosol, cambosol or Cd contaminated ferrosol for two weeks. Polar metabolites of earthworms were detected by nuclear magnetic resonance. Data were then analyzed with principal component analysis followed by orthogonal signal correction-partial least squares-discriminant analysis and univariate analysis to determine possible mechanisms for the changes in metabolites. The survival rates, metal concentrations and bioaccumulation factor (BAF) of the earthworms were also measured and calculated as auxiliary data. The results showed that the metabolite profiles were highly similar in Pb-contaminated ferrosol and cambosol (R² = 0.76, p < 0.0001), which can be attributed to similar response mechanisms. However, there was a more intense response in ferrosol likely due to higher Pb concentrations in earthworms. Metabolic pathways and BAFs exhibited apparent distinctions between Pb- and Cd-contaminated ferrosol, likely because they bind to different bio-ligands. The affected metabolic pathways were involved in alanine-aspartate-glutamate, purine, glutathione, valine-leucine-isoleucine biosynthesis and degradation and nicotinate and nicotinamide metabolism. Regarding the bioavailability in earthworms, Pb availability was higher for ferrosol than for cambosol. We confirmed that the potential toxicity of low Pb/Cd-contaminated soils can be characterized using earthworm metabolomics.

The eco-toxic effects of pesticide and heavy metal mixtures towards earthworms in soil

Earthworms are the key soil organisms, contribute to many positive ecological services that could be degraded by pesticides and other soil pollutants such as heavy metals. Chemicals usually occur as mixtures in the environmental systems which can lead synergistic effects. The assessment and characterization of soil pollutants that effects risks are very difficult due to the complexity of soil matrix, poor understanding about the fate and effects of chemical combinations like pesticide and metal mixtures in terrestrial systems, and scarcity of toxicological data on mixtures of pollutants. In this review we summarized the current studies on individual and joint effects of pesticides and metals on earthworms and indicate the mixture that cause the synergistic interactions. The review explores the methods and models used previously to evaluate the toxicity of chemical mixtures, and suggests the perspective approaches for a better knowledge of combine effects as well as research methods The summarized report indicates that pesticide and metal mixtures at all organization levels affect the earthworms negatively. Whereas, the combined pollution generated by mixtures of pesticides and metal ions could induce the DNA damage, disruption in enzyme activities, reduction in individual survival, production and growth rate, change in individual behavior such as feeding rate, and decrease in the total earthworm community biomass and density. Among the pesticides organophosphates were identified the most toxic pesticides causing the synergistic effects. The findings indicate the scarcity of toxicological data concerning the assessment of pesticide and metal mixtures at genome level; while the mechanisms causing synergism were still not sufficiently explored.

A mechanistic review on vermifiltration of wastewater: Design, operation and performance

With global population explosion, the available water resources are slowly being polluted due to the excessive human interference. To encounter this, it is the need of this hour to find out sustainable pollution remediating technologies to meet the stringent discharge standards for domestic as well as industrial wastewaters. In addition, those techniques should have the capabilities for effective implementation even in developing countries. Based on the available literatures, one such technique, named vermifilter, has been identified which takes care of almost all the sustainable and economical criteria for its effective implementation even in developing countries. The aim of this meta-analysis is to provide a comprehensive review on assessment mechanisms involved, factors affecting the process and performance of vermifiltration under different scenarios. The present review envisages the current state of the knowledge regarding physical, chemical and biological aspects related to the treatment mechanisms and effective functioning of earthworms. This review has also proposed several suggestive plans on its application at any proposed site.

Organic wastes as soil amendments - Effects assessment towards soil invertebrates

Using organic wastes, as soil amendments, is an important alternative to landfilling with benefits to soil structure, water retention, soil nutrient and organic matter concentrations. However, this practice should be monitored for its environmental risk due to the frequent presence, of noxious substances to soil organisms. To evaluate the potential of eight organic wastes with different origins, as soil amendments, reproduction tests with four soil invertebrate species (Folsomia candida, Enchytraeus crypticus, Hypoaspis aculeifer, Eisenia fetida) were performed using gradients of soil-waste mixtures. Results obtained demonstrated that contaminant concentrations required by current legislation might not be a protective measure for the soil ecosystem, as they do not properly translate the potential toxicity of wastes to soil invertebrates. Some wastes with contaminant loadings below thresholds showed higher toxicity than wastes with contaminants concentrations above legal limits. Also, test organism reproduction was differently sensitive to the selected wastes, which highlights the need to account for different organism sensitivities and routes of exposure when evaluating the toxicity of such complex mixtures. Finally this study shows that when combining chemical and ecotoxicological data, it is possible to postulate on potential sources of toxicity, contributing to better waste management practices and safer soil organic amendment products.

Chemosensory cues alter earthworm (Eisenia fetida) avoidance of lead-contaminated soil

Earthworms were shown to significantly avoid soils spiked with Pb at concentrations lower than or comparable to concentrations that demonstrate significant effects for other endpoints. It was also shown that inclusion of a microorganism-produced volatile compound that attracts earthworms, ethyl valerate, decreased avoidance of spiked soils. These findings suggest that care should be taken when analyzing earthworm avoidance of soils in which microorganism communities are not controlled. Environ Toxicol Chem 2017;36:999-1004. © 2016 SETAC.

Microchemical contaminants as forming agents of anthropogenic soils

Within historically accepted, major soil-forming major processes, the role of chemicals as a human-induced factor was neglected until the middle of the last century. Over the years, however, anthropogenic chemicals have emerged and are being released on the land surface in large amounts. Irreversible changes in the matrix of soil and soil constituents may occur as a result of both intentional and accidental release of anthropogenic chemicals, as well as a byproduct of human activity. After presenting an historical evolution of the discussion on soil-forming factors, we focus here on human impacts and examine the abiotic role of anthropogenic microchemical contaminant (AMCC) interactions with soils at the molecular level. Selected examples of microchemical contaminants, including heavy metals, pesticides, hydrocarbons, and engineered nanomaterials, are presented to demonstrate that AMCCs-even at low concentration-may irreversibly alter the matrix of the soil and soil constituents and lead to the formation of anthropogenic soils with different properties than those of the pristine soils.

The effect of lead contamination on bioturbation by Lumbriculus variegatus in a freshwater microcosm

The present study investigated the effect of lead (Pb) on bioturbation by the oligochaete worm Lumbriculus variegatus, using freshwater microcosms. The experiment used lead at "0", 140, 700, and 3500 μg/g in sediment, and used two different laboratory populations of L. variegatus. A molecular genetic analysis and bioassays were conducted to determine if the two populations differed genetically and whether they differed in Pb-sensitivity. The bioturbation of L. variegatus was estimated using luminophores placed at the sediment-water interface at the beginning of the experiment. After the 14 d experiment the luminophore profiles in sediment were used to estimate the biodiffusion and bioadvection coefficients, using the diffusion-advection model. The results showed that the biodiffusion and bioadvection coefficients were generally negatively related to the Pb concentrations in the sediment. Lead at 700 and 3500 μg/g reduced both coefficients, while Pb at 140 μg/g did not. Luminophore profiles in the "0" and 140 μg/g treatments were indicative of a non-local transport, while a diffusive transport was observed at the higher Pb levels. The two laboratory populations of L. variegatus used in the experiment differed in their sensitivity to Pb when mortality was used as the endpoint, but they did not differ in sediment bioturbation or the Pb-sensitivity of this process. Moreover, the genetic analysis did not detect any genetic differences between the populations. This study demonstrated that elevated levels of Pb can impact ecosystem functioning by decreasing the bioturbation activity of benthic organisms such as L. variegatus.

Interactive zinc, iron, and copper-induced phytotoxicity in wheat roots

Growth inhibition and antioxidative response were investigated in wheat roots cultured in 1/4 Hoagland solution containing zinc (Zn, 500 μM), iron (Fe, 300 μM), and copper (Cu, 300 μM) in combination. Different Zn, Fe, and Cu interactions inhibited seedling growth and increased Zn, Fe, and Cu contents in roots and shoots, with the most significant inhibition due to Zn + Fe + Cu treatment. The elevation of malondialdehyde content and the loss of cell viability resulted from the increases of total and apoplastic hydrogen peroxide (H₂O₂) and hydroxyl radical (·OH) contents in all treated roots. Except for Zn + Fe stress, root superoxide anion (O₂^•-) level significantly decreased at other combined treatments. The application of 10 μM diphenylene iodonium suggested that NADPH oxidase activity was lower in Fe + Cu-treated and Zn + Fe + Cu-treated roots than in other roots. Additionally, all combined treatments inhibited superoxide dismutase (SOD) and peroxidase (POD) but stimulated total glutathione reductase (GR) activity in roots. However, in root apoplast, decreased SOD and ascorbate peroxidase activities as well as increased POD, catalase, and GR activities were caused by different Zn, Fe, and Cu interactions. In conclusion, combined Zn, Fe, and Cu stresses exhibited significant inhibition on root growth, with the strongest effect due to Zn + Fe + Cu. Here, it is also indicated that each antioxidantive enzyme including apoplastic enzymes showed specific responses and that the stimulation of some of them played an important protective mechanism against oxidative damage, when wheat roots were treated with different Zn, Fe, and Cu treatments in combination.

Effects of an aged copper contamination on distribution of earthworms, reproduction and cocoon hatchability

Contaminated soil is a problem throughout the industrialized world, and a significant proportion of these sites are polluted with heavy metals such as copper. Ecological risk assessment of contaminated sites requires ecotoxicological studies with spiked soils as well as in-situ ecological observations. Here, we report laboratory and field assessment of copper toxicity for earthworms at a Danish site (Hygum) exclusively contaminated with an increasing gradient in copper from background to highly toxic levels (>1000mgkg^-1 dry soil). More specifically, we report effects on field populations, body contents of copper, hatching of earthworm cocoons and reproduction of the common species Aporrectodea tuberculata. Abundance of earthworms and cocoons decreased significantly from about 400-150m^-2 along the gradient as the soil copper concentration increased from ca. 50 to ca. 1000mgkg^-1. At lower concentrations, the population was dominated by endogeic species, whereas at high concentrations the population was dominated by epigeic species. At high copper contents the internal concentration of copper was in the range 100-160mgkg^-1 dry tissue. Despite the high internal copper contents, hatchability of field collected cocoons was not impaired in any species. The EC50 reproduction value of A. tuberculata was about 220mg copper kg^-1 dry soil in the first two exposure periods, but nearly doubled in the third period suggesting that an acclimation response had occurred. Also in the laboratory reproduction test, cocoon hatchability was not reduced, but rather slightly stimulated by copper. Based on these results we discuss the possibility that acute exposure in laboratory experiments is more detrimental than exposure in a field situation, perhaps because increased tolerance may be acquired through natural selection and genetic adaptation through increased use of defense mechanisms such as metallothioneins. Further, we discuss that the rather high tissue copper level of earthworms from the Hygum site may have smaller effects in these free-ranging worms than it would have in acute-exposure laboratory tests because the copper is more efficiently sequestered and detoxified in the field situation where populations have been exposed for many generations.