Earthworm Accumulation Research Articles

Effects of benzotriazole on copper accumulation and toxicity in earthworm (Eisenia fetida)

Triazole contaminants in water and soil environments can form complexes with metal ions, and therefore affect the bioavailability and toxicity of some heavy metals. In present study, significant increase of copper (Cu) uptake by earthworm (Eisenia fetida) was observed when combined pollution of benzotriazole (BTR) presented in soil. For instance, Cu accumulation in earthworms increased 55% approximately when BTR presented at the BTR/Cu molar ratio of 1:2.5. While the single Cu exposure (at 32 mg kg−1 in soil) resulted in increased malondialdehyde (MDA) content in earthworms from 0.319 to 0.668 nmol mg protein−1, joint exposure to BTR at BTR/Cu molar ratio of 1:10 significantly decreased the MDA content to 0.405 nmol mg protein−1. This indicates a potential detoxification effect of BTR to Cu induced oxidative damage in earthworms. Varied Cu subcellular distribution can be observed in earthworms of the single and combined exposure treatments. With the combined exposure of BTR, the proportion of Cu associated with granular fraction, the toxically inert fraction in earthworms, increased from 25% to 39%. This phenomenon can be used to explain the protective effects of BTR against oxidative damage.

Comparative toxicity and bioaccumulation of two dinotefuran metabolites, UF and DN, in earthworms (Eisenia fetida).

Dinotefuran, as the latest generation of neonicotinoid insecticide, has broad application prospects around the world. However, dinotefuran is easily metabolized and the two main metabolites are 1-methyl-3-(tetrahydro-3-furylmethyl) urea (UF) and 1-methyl-3-(tetrahydro-3-furylmethyl) guanidium dihydrogen (DN). In the present study, the risks of UF and DN in soil on typical non-target species earthworm were investigated. In the same time, the degradation in soil and accumulation in earthworms of UF and DN were monitored. The present results showed that the toxicities of UF and DN were similar in their effect on earthworms and they were supertoxic pollutants to earthworms. The degradation trend in soil and accumulation trend in earthworms of UF and DN were consistent throughout the whole exposure period. At 1.0mg/kg and 2.0mg/kg, UF and DN could induce the excess production of ROS, resulting in oxidative stress effects in earthworm cells. The excess ROS induce changes in antioxidant enzyme activities, damage in biomacromolecules, and abnormal expression of function genes. The present results showed that UF and DN may have high risks for earthworms.

Effects on cranio-facial morphogenesis in embryos exposed in vitro to retinoic acid, valproic acid, and to the antifungal azoles cyproconazole, triadimefon and flusilazole

Elaborating the environmental behavior of mefentrifluconazole, a novel triazole fungicide, in stereoselective level is of paramount importance for the application of the pesticide in agriculture. In this study, the enantioselective bioactivity, acute toxicity and stereoselective bioaccumulation of mefentrifluconazole in earthworm (Eisenia fetida) were investigated. Bioactivity tests against four pathogens revealed that R-(−)-mefentrifluconazole exhibited approximately 11–113 times higher bioactivity than its S-(+)-mefentrifluconazole. However, the LC50 of S-(+)-, rac- and R-(−)-mefentrifluconazole to earthworm was measured to be 4.1, 11.4 and 7.3 μg/cm2, respectively, indicating active ingredient R-(−)-mefentrifluconazole is less toxic than its racemate and S-form. Accumulation of mefentrifluconazole in earthworms was non-enantioselective and negatively related to its adsorption onto soils. The concentration of mefentrifluconazole in in situ pore water (CIPW) and CaCl2 extraction (CCaCl2) was closely related to its accumulation in earthworms, suggesting that CIPW and CCaCl2 could be appropriate indicators for estimation of the bioavailability of mefentrifluconazole in soil. Conclusively, our study provides necessary information for the risk assessment of mefentrifluconazole in agriculture.

English

The present research evaluated the redox ability of Cr6+ in the earthworm Eisenia foetida, and its effects on growth and survival. An assay was conducted with an increasing doses of K2Cr2O7 (0, 200, 400, 800, 1000, and 1200 mg K2Cr2O7 kg-1 substrate) applied to a vermicomposting system which was inoculated with 30 earthworms per chamber. Earthworm growth, estimated by weight, showed a quadratic response (p = 0.03) with the lowest estimated growth at a dose of 435 mg K2Cr2O7 kg-1. Chromium (Cr) concentration increments were positively associated to mortality in adults and cocoons (p < 0.01), and total Cr accumulation in earthworms (p < 0.01). The accumulation of chromium in worms, is an indicator of the capacity of worms to resist different doses of potassium dichromate and, the effect on accumulation of Cr (VI) in vermicomposting was higher (p = 0.11). The difference of potassium dichromate in worms could indicate the oxide reduction in E. fetidae.   Key words: Redox chromium, growth, survival, Eisenia foetida.

Bioavailability assessment of thiacloprid in soil as affected by biochar

Biochars can significantly sorb pesticides, and reduce their bioavailability in agricultural soils. In this study, the effects of a type of biochar (BC500) on the sorption, degradation, bioaccumulation and bioavailability of thiacloprid, which is a commonly used insecticide, were investigated. The thiacloprid sorption constant (Kf values) increased by 14 times after 2% BC500 application, and the degradation of the insecticide decreased with increasing amounts of the biochars in the soil. Coupled with the exhaustive extraction and single-point Tenax method, the bioavailability of thiacloprid was predicted in the presence of the biochar. In soils amended with BC500, the thiacloprid concentrations accumulated in Tenax correlated well with those observed in earthworms (R2 = 0.887), whereas the concentrations extracted by exhaustive method followed a less significant relationship with those in earthworms (R2 = 0.624). The results of Tenax extractions and earthworm bioassays indicate that biochar reduces the bioavailability of thiacloprid in soil, but the delayed degradation and increased earthworm accumulation in aged biochar-amended soil imply that the environmental risks of biochar application to earthworms remain.

Bioaccumulation and bound-residue formation of 14C-decabromodiphenyl ether in an earthworm-soil system

Decabromodiphenyl ether (DecaBDE) is one of the most frequently detected flame retardants in terrestrial environments. However, the fate of DecaBDE and its transport in an earthworm-soil system with and without a DecaBDE-degrading strain have rarely been evaluated. In this study, 14C-DecaBDE was self-synthesized, and a DBDE-degrading strain, Rhodococcus erythropolis, was used in an earthworm-soil system. DecaBDE showed limited degradation and mineralization after 35days of all treatments. The bound-residue (BR) formation in soil was <2.5% in the system containing earthworms, which was significantly higher (p<0.05) than that observed in the absence of earthworms (<0.45%). DecaBDE could be adsorbed by the earthworms with a BSAF of ≤0.31. The distribution of 14C-DecaBDE concentrations in the earthworm roughly followed the pattern of crop gizzard>digestive system>head>tail>body wall, suggesting that DecaBDE was mainly uptaken through ingestion. Up to 31% of the 14C-DecaBDE in the earthworms was not extractable, revealing that the total concentration of accumulated 14C-DecaBDE was underestimated. The results also showed that the presence of DecaBDE-degrading bacteria did not significantly affect the fate of DecaBDE and its accumulation in earthworms. The study indicates that the conventional assessment of the bioaccumulation and ecological effects of DecaBDE, which is based only on extractable concentrations, may underestimate the risks.

A novel bioaccessibility prediction method for PAHs in soil: Composite extraction with hydroxypropyl-β-cyclodextrin and extracellular polymer substances

Hydroxypropyl-β-cyclodextrin (HPCD) extraction has been widely used to estimate bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) in soil, but it often underestimates the actual risk due to lack of information regarding the exogenous active substances, such as extracellular polymer substance (EPS) secreted by microorganisms. In this study, a novel technique, composite extraction of HPCD each with rhamnolipid (RL), bovine serum albumin (BSA) and alginate sodium (AS), models of lipopolysaccharide, proteins and polysaccharides, was developed to assess PAHs bioaccessibility to earthworms. In addition, comparisons were conducted with accelerated solvent extraction (ASE) and individual HPCD extraction. The results demonstrated that all chemical extractions were linearly correlated with earthworm accumulation, and individual HPCD extraction underestimated PAH bioaccessibility by about two times. However, the overall performances of the three composite chemical extractions (HPCD/AS, HPCD/RL, HPCD/BSA) were better than individual HPCD extraction, among which, HPCD/AS was best at estimating the earthworm accumulation (considering both correlation coefficient and fitted linear slope). Therefore, all observations implied that HPCD/AS extraction could be used as a fast and reliable method to predict PAH bioaccessibility to earthworms in contaminated soils.

Effects of metals on earthworm life cycles: a review.

Earthworms are abundant and ecologically very important organisms in the soil ecosystem. Impacts by pollutants on earthworm communities greatly influence the fertility of the terrestrial environment. In ecotoxicology, earthworms are good indicators of metal pollution. The observed median lethal concentrations (LC50) and the effective concentrations that cause 50% reduction of earthworm growth and reproduction (EC50) are referred to as toxicity concentrations or endpoints. In addition, the 'no observed effective concentration' (NOEC) is the estimation of the toxicity of metals on earthworms expressed as the highest concentration tested that does not show effects on growth and reproduction compared to controls. This article reviews the ecotoxicological parameters of LC50, EC50 and NOEC of a set of worms exposed to a number of metals in various tested media. In addition, this article reviews metal accumulation and the influences of soil characteristics on metal accumulation in earthworms. Morphological and behavioural responses are often used in earthworm toxicity studies. Therefore, earthworm responses due to metal toxicity are also discussed in this article.

Does powder and granular activated carbon perform equally in immobilizing chlorobenzenes in soil?

The objective of this study is to compare the efficacies of powder activated carbon (PAC) and granular activated carbon (GAC) as amendments for the immobilization of volatile compounds in soil. Soil artificially-spiked with chlorobenzenes (CBs) was amended with either PAC or GAC to obtain an application rate of 1%. The results showed that the dissipation and volatilization of CBs from the amended soil significantly decreased compared to the unamended soil. The bioavailabilities of CBs, which is expressed as butanol extraction and earthworm accumulation, were significantly reduced in PAC and GAC amended soils. The lower chlorinated and hence more volatile CBs experienced higher reductions in both dissipation and bioavailability in the amended soils. The GAC and PAC equally immobilized more volatile CBs in soil. Therefore, it could be concluded that along with environmental implication, applying GAC was the more promising approach for the effective immobilization of volatile compounds in soil.

Interactive effects between earthworms and maize plants on the accumulation and toxicity of soil cadmium

Multi-species tests are preferable in ecotoxicological studies as they allow the investigation of the influence of ecological interactions on mobility, bioavailability, and toxicity of contaminants. We performed monospecific and combined culture experiments in a soil-maize-earthworm testing system to determine the interactive effects between earthworms and maize plants on the accumulation and toxicity of cadmium (Cd) to each respective species. It was found that the co-presence of maize plants and earthworms in soil promoted the mobility and availability of Cd, but reduced Cd accumulation in earthworms and maize roots and showed little effects on cadmium's accumulation in maize stems and leaves. The presence of plants reduced Cd toxicity to earthworm cocoon output and body mass development, while the presence of earthworms showed no significant effects on Cd toxicity to maize shoot and root biomass. Meanwhile, the presence of earthworms reversed the effects of Cd on soil microbial community and stimulated and increased maize rhizosphere microbial species. It was concluded that the increase of metal mobility and availability in a multi-species testing system does not necessarily indicate a corresponding increase of ecotoxicity, and the interspecific effects between species belonging to different trophic levels on the accumulation and toxicity of metals should be taken into account in ecotoxicological risk assessment.

Predicting PAHs bioavailability for earthworms by mild solvents and Tenax extraction

The total concentration of organic contaminants in soil often overestimates their environmental risk, it is thus important to establish time- and cost-efficient chemical techniques for predicting their bioavailability. In the present study, three chemical extractions, namely: Tenax extraction, butanol extraction and HPCD extraction, were conducted to predict PAHs bioavailability in soil for earthworms. The results showed that earthworm accumulations had less correlation with total concentrations except for PAHs of low molecular weight (R2–3 PAHs). Fractions extracted by butanol/HPCD correlated to earthworm accumulated PAHs of low molecular weight (R2–3 PAHs), but not to earthworm accumulated PAHs of high molecular weight (R5–6 PAHs). Tenax 6h-extracted PAHs had significantly linear correlations with earthworm accumulated R2–3 PAHs, R4 PAHs as well as R5–6 PAHs (associated R2 were 0.96, 0.98 and 0.97, respectively). Furthermore, Tenax 6h-extracted concentrations were comparable to earthworm accumulations for R2–3, R4 as well as R5–6 PAHs. These observations verified that Tenax 6h extraction is better than butanol and HPCD extractions to predict earthworm accumulation of PAHs in soil. Tenax 6h extraction can serve as a good technique to assess PAHs bioavailability for earthworms.

Chemical extraction to assess the bioavailability of chlorobenzenes in soil with different aging periods

Bioavailability is mainly influenced by aging and desorption of contaminants in soil. The purpose of this study was to investigate the desorption kinetics of chlorobenzenes (CBs) in soil and to investigate whether chemical extractions are suitable for the bioavailability assessment of CBs in soil. A soil spiked with CBs and aged for different periods was extracted with Tenax, hydroxypropyl-β-cyclodextrin (HPCD), and butanol to assess the bioavailability of CBs in soil, respectively. Earthworm (Eisenia foetida) accumulation was used as bioassay in parallel experiments to evaluate the chemical extractions. The results showed that desorption of CBs from soil with consecutive Tenax extraction fitted into triphasic kinetics model. Different chemical methods extracted different amounts of CBs over different aging periods. For hexachlorobenzene (HCB), the extraction efficiency was in the order of butanol > Tenax-6h > HPCD extraction, while the order of butanol > HPCD > Tenax-6h extraction for pentachlorobenzene (PeCB). The bioaccumulation by earthworm decreased with increasing aging period and was significantly higher for HCB than for PeCB (p < 0.05). Earthworm accumulated CBs correlated well with all the three chemical extracted CBs. However, HPCD extraction showed the converse extraction tendency with earthworm uptake of CBs. Chemical extraction could be used to assess the bioavailability of contaminants in soil; however, they were method and compound specific. Tenax and butanol extractions were more reliable than HPCD extraction for bioavailability assessment of the tested CBs and the soil used since they showed the consistent extraction tendency with earthworm uptake of CBs.

Effects of aging and mixed nonaqueous‐phase liquid sources in soil systems on earthworm bioaccumulation, microbial degradation, sequestration, and aqueous desorption of pyrene

The effects of loading and aging pyrene in soils in the presence of four environmentally common nonaqueous-phase liquids (NAPLs) (hexadecane, 2,2,4,4,6,8,8-heptamethylnonane [HMN], toluene, and dimethyl phthalate [DMP]) on its subsequent desorption from those soils, earthworm accumulation, biodegradation, and extractability were tested by using two dissimilar soils. The presence of each of the four NAPLs increased fractions and rates of pyrene desorption, and hexadecane slowed the effects of aging on these same parameters. Loading with hexadecane and HMN caused earthworm accumulation of pyrene to decrease. These results contrast with generally observed faster desorption rates resulting from NAPL addition, suggesting that additional factors (e.g., association of pyrene with NAPL phases and NAPL toxicities to earthworms) may impact bioaccumulation. The presence of HMN and toluene increased pyrene biodegradation, whereas hexadecane and DMP had the opposite effects. These results correlate with changes in the extractability of pyrene from the soils. After aging and biodegradation, hexadecane and DMP substantially increased pyrene residues extractable by methanol and decreased nonextractable fractions, whereas HMN and toluene had the opposite effects.

Environmental monitoring of the role of phosphate compounds in enhancing immobilization and reducing bioavailability of lead in contaminated soils

Lead is a highly toxic element and forms stable compounds with phosphate, which is commonly used to immobilize Pb in soils. However, few studies have monitored the long-term stability of immobilized Pb, which is a critical factor in determining the effectiveness of the in situ stabilization technique. Both soluble and insoluble phosphate compounds were tested for Pb immobilization, and its subsequent mobility and bioavailability in a contaminated soil from a shooting range. Adding tricalcium phosphate, hydroxyapatite, rock phosphate and potassium dihydrogen phosphate reduced the concentration of ammonium-nitrate-extractable Pb in the contaminated soil by 78.6%, 48.3%, 40.5% and 80.1%, respectively. Insoluble phosphate amendments significantly reduced leached Pb concentration from the column while soluble potassium dihydrogen phosphate compound increased P and Pb concentrations in the leachate. Rock phosphate reduced Pb accumulation in earthworms by 21.9% compared to earthworms in the control treatment. The long-term stability of immobilized Pb was evaluated after 2 years' incubation of the contaminated soil with rock phosphate or soluble phosphate compounds. Bioavailable Pb concentration as measured by simple bioavailability extraction test (SBET) showed the long-term stability of immobilized Pb by P amendments. Therefore, Pb immobilization using phosphate compounds is an effective remediation technique for Pb-contaminated soils.

Relative proportions of polycyclic aromatic hydrocarbons differ between accumulation bioassays and chemical methods to predict bioavailability

Chemical methods to predict the bioavailable fraction of organic contaminants are usually validated in the literature by comparison with established bioassays. A soil spiked with polycyclic aromatic hydrocarbons (PAHs) was aged over six months and subjected to butanol, cyclodextrin and tenax extractions as well as an exhaustive extraction to determine total PAH concentrations at several time points. Earthworm ( Eisenia fetida) and rye grass root ( Lolium multiflorum) accumulation bioassays were conducted in parallel. Butanol extractions gave the best relationship with earthworm accumulation ( r 2 ≤ 0.54, p ≤ 0.01); cyclodextrin, butanol and acetone–hexane extractions all gave good predictions of accumulation in rye grass roots ( r 2 ≤ 0.86, p ≤ 0.01). However, the profile of the PAHs extracted by the different chemical methods was significantly different ( p < 0.01) to that accumulated in the organisms. Biota accumulated a higher proportion of the heavier 4-ringed PAHs. It is concluded that bioaccumulation is a complex process that cannot be predicted by measuring the bioavailable fraction alone.

Cadmium bioaccumulation factors for terrestrial species: Application of the mechanistic bioaccumulation model OMEGA to explain field data

In environmental risk assessment of metals it is often assumed that the biota-to-soil accumulation factor (BSAF) is generic and constant. However, previous studies have shown that cadmium bioaccumulation factors of earthworms and small mammals are inversely related to total soil concentrations. Here, we provide an overview of cadmium accumulation in terrestrial species belonging to different trophic levels, including plants, snails and moles. Internal metal concentrations of these species are less than linearly related to total soil levels, which is in accordance with previously observed trends. The mechanistic bioaccumulation model OMEGA (Optimal Modeling for Ecotoxicological Applications) is used to provide a quantitative explanation of these trends in cadmium accumulation. Our results indicate that the model accurately predicts cadmium accumulation in earthworms, voles and shrews when accounting for geochemical availability of metals and saturable uptake kinetics.

The impact of cadmium and mercury contamination on reproduction and body mass of earthworms

The accumulation of heavy metals in the tissues of earthworms is a helpful indicator of environmental contamination. The degree of substrate contamination can be additionally evaluated on the basis of survivability, reproduction and body mass of earthworms. In this study &lt;I&gt;Eisenia fetida&lt;/I&gt; Sav. earthworms were exposed to a series of increasing concentrations of cadmium and mercury. The numbers of animals and their body mass were checked after 4 and 8 months. The strongest impact of substrate contamination was exerted upon the number of young individuals and cocoons. The cadmium contamination did not affect adversely the mass of earthworms, whereas in the mercurycontaminated group the decline in body mass was evident. After 8 months of experiments, the content of heavy metal in the bodies of earthworms was determined. An evident relationship between the cadmium and mercury contents in the substrate and their accumulation in earthworms’ tissues was found. The concentration in the bodies exceeded the level in the substrate.

Cadmium accumulation in herbivorous and carnivorous small mammals: Meta‐analysis of field data and validation of the bioaccumulation model optimal modeling for ecotoxicological applications

Environmental risk assessment procedures often use bioaccumulation as a criterion for hazard identification of a polluted location. Field studies regarding metal concentrations in food chains, however, have provided widely different information, because accumulation is shown to vary between the extremes of bioreduction and biomagnification. Bioaccumulation models provide insight regarding species-specific uptake and elimination kinetics of metals and assist in the interpretation of field data. Here, we use the bioaccumulation model OMEGA (Optimal Modeling for Ecotoxicological Applications) to estimate cadmium accumulation in herbivorous voles and carnivorous shrews. In addition to model validation, a meta-analysis of cadmium accumulation data is performed, because earlier studies generally have focused on relationships between cadmium concentrations in either specific tissues (kidney and liver) or whole-body concentrations and total soil levels. Additionally, we included the food-small mammal relationship. Our results show that cadmium whole-body concentrations are significantly related to cadmium levels in food items such as earthworms and plants. In addition, a significant relationship is found between cadmium accumulation in the liver and kidney of small mammals and total soil levels. Cadmium concentrations in shrews typically are an order of magnitude higher than metal levels in voles as a result of higher metal accumulation in earthworms compared to plants. Model predictions for both voles and shrews are in good agreement with field observations; deviations generally are within a factor of five. Small mammals prevent cadmium toxicity by binding this metal to metallothionein, which likely results in low elimination rates. Comparison with empirical elimination rates shows that rate constants of loss are accurately predicted assuming that cadmium is only released via growth dilution.

Metal accumulation in earthworms inhabiting floodplain soils

The main factors contributing to variation in metal concentrations in earthworms inhabiting floodplain soils were investigated in three floodplains differing in inundation frequency and vegetation type. Metal concentrations in epigeic earthworms showed larger seasonal variations than endogeic earthworms. Variation in internal levels between sampling intervals were largest in earthworms from floodplain sites frequently inundated. High and low frequency flooding did not result in consistent changes in internal metal concentrations. Vegetation types of the floodplains did not affect metal levels in Lumbricus rubellus, except for internal Cd levels, which were positively related to the presence of organic litter. Internal levels of most essential metals were higher in spring. In general, no clear patterns in metal uptake were found and repetition of the sampling campaign will probably yield different results.

Effect of pH on metal speciation and resulting metal uptake and toxicity for earthworms

In the present study, relationships between changes in the solubility and speciation of metals in contaminated soils under different pH regimes and their toxicity to earthworms were investigated. Earthworms (Lumbricus rubellus) were exposed in a laboratory bioassay to metalliferous soils under three pH regimes: Unamended pH, pH lowered by one unit (pH -1), and pH increased by one unit (pH +1). In each soil, total (hot nitric acid-extractable) and 0.01 M CaCl2-extractable metal concentrations were measured and soil pore-water chemistry analyzed to allow metal speciation to be modeled using the Windermere Humic Aqueous Model. Earthworm metal accumulation was determined and toxicity assessed by measuring survival and reproduction and at the molecular level by recording expression of the gene encoding metallothionein-2 (MT-2) using quantitative reverse transcriptase-polymerase chain reaction. Both metal solubility and speciation were found to be highly pH dependent. Metal accumulation in earthworms was influenced by soil concentration and, in some cases (e.g., Cd), by pH. Reproduction was affected (reduced up to 90%) by soil metal level, pH, and their interaction. Relationships between analyzed and calculated Zn concentrations and toxicity and between analyzed and calculated Cd concentrations and tissue accumulation and MT-2 expression were compared by fitting dose-response models and assessing the fit of the data. This analysis indicated that values based on a pH-adjusted free ion concentration best explained toxicity (r2 = 0.82) and accumulation (r2 = 0.54). Expression of MT-2 was, however, poorly correlated (p > 0.05) with all analyzed and modeled soil metal concentrations.