Toxicity of chromium(III) and chromium(VI) to the earthworm Eisenia fetida

Dual role of pyrogenic carbon in mediating electron transfer from clay minerals to chromium in aqueous and solid media

Clay minerals (CMs) and pyrogenic carbons (PCs) often co-exist in the environment and participate in the redox cycling of pollutants. This study unveiled the dual role of PCs in CM-dominated chromium transformation in both aqueous and agar solidification media. The findings showed that CMs and PCs adsorbed minimal Cr(VI), while reduced CMs and PCs displayed a substantial difference by directly reducing Cr(VI) to solid/dissolved Cr(III) through reactive structural Fe(II) and functional groups, respectively. Moreover, dissolved PCs were found to mediate electron transfer from reduced CMs to Cr(VI) in aqueous and solid media. Interestingly, the effect of solid PCs on Cr(VI) reduction by reduced CMs was concentration-dependent. At lower concentrations, solid PCs dispersed reduced CMs, acting as electron mediators and facilitating both direct and indirect Cr(VI) reduction, resulting in solid Cr(III) rather than dissolved Cr(III). Conversely, at higher concentrations, solid PCs served as redox buffers, storing electrons transferred from reduced CMs to Cr(VI). In either case, the transformed chromium was primarily immobilized on the surface of CMs rather than PCs. These findings offer valuable insights into pollutant transformations associated with CMs and PCs, deepening our understanding of their geochemical processes.

Toxicokinetics and toxicodynamics of chromium in the soil invertebrate Enchytraeus crypticus (Oligochaeta)

Chromium emissions led to increased concentrations in soil, where it can affect soil organisms to relevant levels. With the aim of better understanding the effects of Cr throughout time, its toxicokinetics-toxicodynamics (TKTD) were evaluated in the soil model organism Enchytraeus crypticus to assess the development of internal concentrations and consequent toxic effects. To achieve this goal, organisms were exposed in LUFA 2.2 soil spiked with increasing CrCl₃ concentrations. During the 21-day exposure period, survival, internal concentrations, and reproduction were evaluated at several time points up to 21 days. Uptake and elimination rate constants were 0.0044 kg soil/kg organism/day and 0.023 per day, respectively. Internal Cr concentrations increased with time, generally reaching equilibrium within 14 days with an estimated LC50_inter (based on internal metal concentrations) of 57.7 mg Cr/kg body DW. Internal Cr concentrations were regulated by the organisms up to exposure to 360 mg Cr/kg soil DW, where the elimination rate was highest, but at 546 mg Cr/kg soil DW the animals were no longer able to eliminate Cr, and the internal concentrations were well above the estimated LC50_inter. At day 21, exposure to 546 mg Cr/kg soil DW significantly reduced survival by 23 %, while reproduction EC50 was 344 mg Cr/kg soil DW. This study highlights the advantages of using a TKTD approach to understand the development of internal metal concentrations in time and relate it to the phenotypical effects observed. Toxicity is better understood when also taking into account time and not just exposure concentration alone.

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

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

Partial Oxidation of FeS Nanoparticles Enhances Cr(VI) Sequestration

Iron sulfide nanoparticles (nano-FeS) have shown great potential for in situ remediation of Cr(VI) pollution by reducing Cr(VI) to the less soluble and toxic Cr(III). However, material oxidation that inevitably occurs during storage and application alters its reactivity. Herein, we show that partial oxidation of nanoparticulate mackinawite (FeS) significantly enhances its capability in sequestering Cr(VI). Oxidation of nano-FeS increases its binding affinity to Cr(VI), likely due to preferential inner-sphere complexation of Cr(VI) oxyanions to ferric over ferrous iron in mackinawite/lepidocrocite (FeS/γ-FeOOH) nanocomposites. A trade-off is that oxidation mitigates Cr(VI) reduction by lowering the electron-donating potential of the material and the electron transfer at a solution-material interface and consequently hinders the transformation of adsorbed Cr(VI) to Cr(III). Notably, the rate-limiting step of Cr(VI) sequestration transitions from adsorption to reduction during oxidation, as demonstrated with batch experiments coupled with kinetic modeling. Thus, an optimum oxidation degree exists, wherein the gain in the overall performance from enhanced adsorption overcompensates the loss from inhibited reduction, resulting in maximum sequestration of aqueous Cr(VI) as solid-phase Cr(III). Our findings inform better assessment and design of nanomaterials for Cr(VI) remediation and may be extended to interactions of other oxyanions with natural and engineered nanoparticles during oxidative aging.

Hexavalent chromium induces hepatocyte apoptosis via regulation of apoptosis signal-regulating kinase 1/c-Jun amino-terminal kinase signaling

With the spread of hexavalent chromium (Cr(VI)) contamination, Cr(VI)-induced hepatotoxicity has attracted increasing attention in recent years. To date, however, the exact mechanism of Cr(VI) toxicity remains unclear. In this study, we investigated the role of apoptosis signal-regulating kinase 1 (ASK1)/c-Jun amino-terminal kinase (JNK) in Cr(VI)-induced hepatic toxicity and the possible related mechanisms. AML-12 hepatocyte cell-lines were treated with 0, 1, 4, and 16 μmol/Lof Cr(VI) with or without GS-444271 (an ASK1 inhibitor). Adult male mice were administered with 0, 2, 8, and 32 mg/kg body mass (BM)/day of Cr(VI) for 5 days. The level of hepatocyte apoptosis/proliferation, generation of reactive oxygen species (ROS), and expression levels of mRNAs and proteins related to ASK1/JNK and nuclear factor-E2-related factor 2 (Nrf2) signaling were assessed. Results showed that high Cr(VI) exposure induced hepatocyte apoptosis and liver injury by generation of ROS and down-regulation of Nrf2 signaling. In addition, ASK1/JNK signaling activity was upregulated in the Cr(VI)-treated group. Furthermore, GS-444217 treatment significantly rescued Cr(VI)-induced hepatocyte apoptosis and liver dysfunction in vitro and in vivo by down-regulation of ASK1/JNK signaling. Thus, ASK1/JNK signaling appears to play an important role in Cr(VI)-induced hepatocyte apoptosis and liver injury. This study should help improve our understanding of the mechanism of Cr(VI)-induced liver injury and provide support for future investigations on liver disease therapy.

Metal accumulation and morphofunctional damage in coelomocytes of earthworm collected from industrially contaminated soil of Kolkata, India

The current study is aimed to assess the ecotoxicological effects of toxic metals and seasonal shift of the physicochemical characteristics of soil in an endogeic earthworm Metaphire posthuma of industrially contaminated soil of Calcutta leather complex. The accumulation of cadmium, chromium, lead and mercury was quantitated in whole earthworms and coelomocytes. The accumulation of metals was derived to be high in the coelomocytes than whole earthworms. Morphofunctional shift in coelomocytes indicated a high level of metal toxicity in soil inhabitants. The shift in differential coelomocyte count and cellular damage including intense cytoplasmic vacuolation and membrane blebbing of coelomocytes of M. posthuma of contaminated soil were suggestive to a state of immunocompromisation in the same species. Shift in the generation of nitric oxide and activity of inducible nitric oxide synthase indicated a possible immunosuppression in earthworm. Depletion in the acetylcholinesterase activity of coelomocytes indicated neurotoxicity of metals leached from the dumped wastes in Calcutta leather complex. Integrated biomarker response based analysis was carried out to assess the biomarker potential of experimental endpoints of M. posthuma to monitor metal toxicity in soil.

The toxicity of hexavalent chromium to soil microbial processes concerning soil properties and aging time

Chromium (Cr) pollution has attracted much attention due to its biological toxicity. However, little is known regarding Cr toxicity to soil microorganisms. The present study assesses the toxicity of Cr(VI) on two microbial processes, potential nitrification rate (PNR) and substrate-induced respiration (SIR), in a wide range of agricultural soils and detected the abundance of soil bacteria, fungi, ammonia-oxidizing bacteria and archaea. The toxicity thresholds of 10% and 50% effective concentrations (EC₁₀ and EC₅₀) for PNR varied by 32.18- and 38.66-fold among different soils, while for SIR they varied by 391.21- and 16.31-fold, respectively. Regression model analysis indicated that for PNR, CEC as a single factor explained 27% of the variation in EC₁₀, with soil clay being the key factor explaining 47.3% of the variation in EC₅₀. For SIR, organic matter and pH were found to be the most vital predictors for EC₁₀ and EC₅₀, explaining 34% and 61.1% of variation, respectively. In addition, extended aging time was found to significantly attenuate the toxicity of Cr on PNR. SIR was mainly driven by total bacteria rather than fungi, while PNR was driven by both AOA and AOB. These results were helpful in deriving soil Cr toxicity threshold based on microbial processes, and provided a theoretical foundation for ecological risk assessments and establishing a soil environmental quality criteria for Cr.

Impact of chromium on the soil invertebrate model Enchytraeus crypticus (Oligochaeta) in standard reproduction and full life cycle tests

Chromium (Cr) has many applications in industry and day-to-day life, entering the terrestrial environment mostly from anthropogenic sources. Despite the fact that Cr is essential, it can be harmful in biota at high concentrations. Full life cycle tests (FLCt) are scarce, representing a gap for soil ecotoxicology. Hence, the effects of Cr were studied using the soil organism Enchytraeus crypticus in the 46-day FLCt and the standard 21-day enchytraeid reproduction test (ERT). FLCt hatching (day-11) and time to reach maturity (day 22-25) were the most sensitive endpoints, representing a delay, partly recovered with time. Reproduction was reduced to similar levels in both the ERT and the FLCt (EC₅₀∼320 mg Cr/kg), but survival was more affected in the ERT (LC₅₀ = 377 mg Cr/kg) than in the FLC (LC₅₀ = 467 mg Cr/kg). This could be due to the induction of stress response mechanisms at earlier life stages (cocoons/juveniles), providing protection to toxicity in a later stage (adults). FLCt results provided considerably more details and data points, and the additional endpoints allowed to explain the source of observed effects, e.g. a direct impact on fecundity and not only due to adult mortality. The estimated population growth curves confirmed the significant effect of 320 mg Cr/kg and onwards, reflecting the impact of Cr on both cocoon production and juvenile performance, with follow-up consequences for reproduction. An Adverse Outcome Pathway was drafted. The FLCt design is recommended as an upgrade of the current standard ERT, which could be integrated into the existing OECD ERT test guideline.

Toxicokinetics of Chromium in Enchytraeus crypticus (Oligochaeta)

Chromium is naturally occurring, but emission from anthropogenic sources can lead to increased soil concentrations. Information on its toxicokinetics is essential in order to understand the time needed to reach toxicity and the mechanisms of uptake/elimination. In this study the toxicokinetics of Cr(III) was evaluated using the soil standard species Enchytraeus crypticus. The animals were exposed to 180 mg Cr/kg dry soil, a sublethal concentration, in LUFA 2.2 natural soil. OECD guideline 317 was followed, with a 14-day uptake phase in spiked soil followed by a 14-day elimination in clean soil. Exposure to Cr led to fast uptake and elimination, with K_u = 0.012 kg_soil/kg_organism/day and K_e = 0.57 day⁻¹. The bioaccumulation factor was 0.022, and DT₅₀ for elimination was 1.2 days. The concentration of Cr reached an internal equilibrium in the animals after 10 days. Transfer to clean soil allowed body Cr concentrations to return to background levels after approximately 7 days. E. crypticus seemed able to efficiently regulate internal Cr concentrations by actively eliminating Cr (an essential element). Although K_u and K_e deviated from the values reported in other studies for other soil invertebrates, the bioaccumulation factors were similar. These findings show the importance of toxicokinetic studies in evaluating toxicity based on internal metal concentrations that can more accurately represent the bioavailable concentration.

Antifouling paint particles in soils: toxic impact that goes beyond the aquatic environment

Antifouling paint particles (APPs) originate from vessel maintenance and cleaning activities and their potentially toxic components are found at high concentrations in nearby soils, yet no studies have investigated their toxicity to soil organisms. We investigated the effects of exposure to soils containing APPs on the mortality, biomass, and reproductive performance of the earthworm Eisenia andrei. Earthworms were exposed to contaminated soil from a boatyard and non-contaminated soils treated with different concentrations of APPs (0.01, 0.14 and 1.50%, w/w) for 56 days. An ecological risk assessment using a Hazard Quotient (HQ) was also carried out. Exposure to contaminated soils reduced worm survival, biomass, and reproductive performance and these effects were concentration-dependent. The HQ was high in soil samples with APPs in both acute and chronic tests, and copper contributed the most to the HQ. Copper, zinc, and lead had the highest concentrations and exceeded the Brazilian legal limits. A principal component analysis (PCA) was performed and showed that biomass and number of juveniles parameters was associated with the metals Cu, Sn and Zn, while the mortality parameter had no association with any analyzed metal. These findings highlighted that the synergistic effects of compounds present in the APPs, such as the booster biocides DCOIT, and metal mixtures should not be overlooked. We conclude that soils contaminated with APPs are toxic to earthworms. This reveals that the ecological impact of APPs goes beyond effects on aquatic environments, compromising key organisms of edaphic ecological processes.

Direct embryotoxicity of chromium (III) exposure during preimplantation development

Chromium in its trivalent form (chromium (III)) is an essential component of a balanced diet, and its deficiency disturbs glucose and lipid metabolism in humans and animals. The prevailing view is that chromium (III) is notably less toxic than chromium (VI), which is genotoxic and carcinogenic. Thus, the biotransformation of environmental chromium (VI) to chromium (III) is a promising and environmentally friendly detoxification method. However, increasing evidence suggests that chromium (III) induces considerable cytotoxicity. However, the toxicity of chromium (III) to early embryos remains largely unknown. In the present study, we used in vitro fertilization (IVF) to produce mouse embryos and identified the direct embryotoxicity of chromium (III). On exposure to high concentrations of CrCl₃, blastocyst formation almost completely failed and a large proportion of embryos were arrested at the 2- to 4-cell stage. At low concentrations of CrCl₃, IVF embryos showed a significant decrease in blastocyst formation, reduced total cell numbers, aberrant lineage differentiation, increased oxidative stress, and apoptosis. We also found that chromium (III) exposure during the preimplantation stage, even at low concentrations, led to impaired post-implantation development. Thus, our study substantiates the direct embryotoxicity of chromium (III) during preimplantation development and prolonged impairment of development potential. The results further highlight the potential adverse effects of chromium (III) on public reproductive health with respect to increased environmental enrichment of and dietary supplementation with chromium (III) complexes.

Successful remediation of soils with mixed contamination of chromium and lindane: Integration of biological and physico-chemical strategies

Soils contaminated by organic and inorganic pollutants like Cr(VI) and lindane, is currently a main environmental challenge. Biological strategies, such as biostimulation, bioaugmentation, phytoremediation and vermiremediation, and nanoremediation with nanoscale zero-valent iron (nZVI) are promising approaches for polluted soil health recovery. The combination of different remediation strategies might be key to address this problem. For this reason, a greenhouse experiment was performed using soil without or with an organic amendment. Both soils were contaminated with lindane (15 mg kg^-1) and Cr(VI) (100 or 300 mg kg^-1). After one month of aging, the following treatments were applied: (i) combination of bioaugmentation (actinobacteria), phytoremediation (Brassica napus), and vermiremediation (Eisenia fetida), or (ii) nanoremediation with nZVI, or (iii) combination of biological treatments and nanoremediation. After 60 days, the wellness of plants and earthworms was assessed, also, soil health was evaluated through physico-chemical parameters and biological indicators. Cr(VI) was more toxic and decreased soil health, however, it was reduced to Cr(III) by the amendment and nZVI and, to a lesser extent, by the biological treatment. Lindane was more effectively degraded through bioremediation. In non-polluted soils, nZVI had strong deleterious effects on soil biota when combined with the organic matter, but this effect was reverted in soils with a high concentration of Cr(VI). Therefore, under our experimental conditions bioremediation might be the best for soils with a moderate concentration of Cr(VI) and organic matter. The application of nZVI in soils with a high content of organic matter should be avoided except for soils with very high concentrations of Cr(VI). According to our study, among the treatments tested, the combination of an organic amendment, biological treatment, and nZVI was shown to be the strategy of choice in soils with high concentrations of Cr(VI) and lindane, while for moderate levels of chromium, the organic amendment plus biological treatment is the most profitable treatment.

The impact of increased flooding occurrence on the mobility of potentially toxic elements in floodplain soil - A review

The frequency and duration of flooding events is increasing due to land-use changes increasing run-off of precipitation, and climate change causing more intense rainfall events. Floodplain soils situated downstream of urban or industrial catchments, which were traditionally considered a sink of potentially toxic elements (PTEs) arriving from the river reach, may now become a source of legacy pollution to the surrounding environment, if PTEs are mobilised by unprecedented flooding events. When a soil floods, the mobility of PTEs can increase or decrease due to the net effect of five key processes; (i) the soil redox potential decreases which can directly alter the speciation, and hence mobility, of redox sensitive PTEs (e.g. Cr, As), (ii) pH increases which usually decreases the mobility of metal cations (e.g. Cd²⁺, Cu²⁺, Ni²⁺, Pb²⁺, Zn²⁺), (iii) dissolved organic matter (DOM) increases, which chelates and mobilises PTEs, (iv) Fe and Mn hydroxides undergo reductive dissolution, releasing adsorbed and co-precipitated PTEs, and (v) sulphate is reduced and PTEs are immobilised due to precipitation of metal sulphides. These factors may be independent mechanisms, but they interact with one another to affect the mobility of PTEs, meaning the effect of flooding on PTE mobility is not easy to predict. Many of the processes involved in mobilising PTEs are microbially mediated, temperature dependent and the kinetics are poorly understood. Soil mineralogy and texture are properties that change spatially and will affect how the mobility of PTEs in a specific soil may be impacted by flooding. As a result, knowledge based on one river catchment may not be particularly useful for predicting the impacts of flooding at another site. This review provides a critical discussion of the mechanisms controlling the mobility of PTEs in floodplain soils. It summarises current understanding, identifies limitations to existing knowledge, and highlights requirements for further research.

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.

The Effect of Flooding and Drainage Duration on the Release of Trace Elements from Floodplain Soils

Floodplains downstream of urban catchments are sinks for potentially toxic trace elements. An intensification of the hydrological cycle and changing land use will result in floodplains becoming inundated for longer durations in the future. We collected intact soil cores from a floodplain meadow downstream of an urban catchment and subjected them to an inundation/drainage cycle in the laboratory to investigate the effect of flood duration on trace element concentrations in the soil porewater. The porewater concentrations of Ni, Cr, and Zn increased, whereas Cu and Pb decreased with flood duration. All the Cr present in porewaters was identified as Cr(III). Copper concentrations increased after drainage but Pb mobility remained suppressed. Both pH and dissolved organic carbon (DOC) increased with flood duration but were lower in treatments that were drained for the longest duration (which were also the treatments flooded for the shortest duration). The porewater concentrations of Cr and Ni decreased after drainage to levels below those observed before inundation, mirroring the DOC concentrations. We concluded that the duration of floodplain inundation does have an influence on the environmental fate of trace elements but that flooding does not influence all trace elements in the same way. The implications of an intensification of the hydrological cycle over the coming decades are that floodplains may become a source of some trace elements to aquatic and terrestrial ecosystems. Environ Toxicol Chem 2020;39:2124-2135. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Deciphering the toxic effects of metals in gold mining area: Microbial community tolerance mechanism and change of antibiotic resistance genes

Mine tailing dumps represent significant threats to ecological environments due to the presence of toxic substances. The present work investigated the relationship among microbial activity, the community, antibiotic resistance genes (ARGs) and trace metals in soil surrounding gold mine tailings. Using microbial metabolic activity and high-throughput sequencing analysis, we found the trace metals Cd and Hg could be main factors influencing the microbial community. According to bacterial co-occurrence pattern analysis, the effects of total cadmium and total mercury on bacterial diversity are potentially mediated by influencing bacteria community in the keystone module II. Additionally, most of metal-resistant bacteria belong to Actinobacteria and Proteobacteria, and the metal tolerance suggested to be linked with various functions including replication, recombination and repair, as well as inorganic ion transport and metabolism based on PICRUSt2 analysis. We also found that metals generated by mining activity may trigger the co-selection of antibiotic resistance in the phyla Actinobacteria and Proteobacteria due to co-resistance or cross resistance. Additionally, PLS-PM analysis revealed that metals could indirectly affect ARGs by influencing bacterial diversity in gold mining areas.

Toxicity of binary mixtures of Cu, Cr and As to the earthworm Eisenia andrei

Chromated copper arsenate (CCA) mixtures were used in the past for wood preservation, leading to large scale soil contamination. This study aimed at contributing to the risk assessment of CCA-contaminated soils by assessing the toxicity of binary mixtures of copper, chromium and arsenic to the earthworm Eisenia andrei in OECD artificial soil. Mixture effects were related to reference models of Concentration Addition (CA) and Independent Action (IA) using the MIXTOX model, with effects being related to total and available (H₂O and 0.01 M CaCl₂ extractable) concentrations in the soil. Since only in mixtures with arsenic dose-related mortality occurred (LC₅₀ 92.5 mg/kg dry soil), it was not possible to analyze the mixture effects on earthworm survival with the MIXTOX model. EC₅₀s for effects of Cu, Cr and As on earthworm reproduction, based on total soil concentrations, were 154, 449 and 9.1 mg/kg dry soil, respectively. Effects of mixtures were mainly antagonistic when related to the CA model but additive related to the IA model. This was the case when mixture effects were based on total and H₂O-extractable concentrations; when based on CaCl₂-extractable concentrations effects mainly were additive related to the CA model except for the Cr-As mixture which acted antagonistically. These results suggest that the CCA components do interact leading to a reduced toxicity when present in a mixture.

Immobilization of Cr(VI) in Soil Using a Montmorillonite-Supported Carboxymethyl Cellulose-Stabilized Iron Sulfide Composite: Effectiveness and Biotoxicity Assessment

A novel composite of montmorillonite-supported carboxymethyl cellulose-stabilized nanoscale iron sulfide (CMC@MMT-FeS), prepared using the co-precipitation method, was applied to remediate hexavalent chromium (Cr(VI))-contaminated soil. Cr(VI)-removal capacity increased with increasing FeS-particle loading. We tested the efficacy of CMC@MMT-FeS at three concentrations of FeS: 0.2, 0.5, and 1 mmol/g, hereafter referred to as 0.2 CMC@MMT-FeS, 0.5 CMC@MMT-FeS, and 1.0 CMC@MMT-FeS, respectively. The soil Cr(VI) concentration decreased by 90.7% (from an initial concentration of 424.6 mg/kg to 39.4 mg/kg) after 30 days, following addition of 5% (composite-soil mass proportion) 1.0 CMC@MMT-FeS. When 2% 0.5 CMC@MMT-FeS was added to Cr(VI)-contaminated soil, the Cr(VI) removal efficiency, as measured in the leaching solution using the toxicity characteristic leaching procedure, was 90.3%, meeting the environmental protection standard for hazardous waste (5 mg/kg). The European Community Bureau of Reference (BCR) test confirmed that the main Cr fractions in the soil samples changed from acid-exchangeable fractions to oxidable fractions and residual fractions after 30 days of soil remediation by the composite. Moreover, the main complex formed during remediation was Fe(III)-Cr(III), based on BCR and X-ray photoelectron spectroscopy analyses. Biotoxicity of the remediated soils, using Vicia faba and Eisenia foetida, was analyzed and evaluated. Our results indicate that CMC@MMT-FeS effectively immobilizes Cr(VI), with widespread potential application in Cr(VI)-contaminated soil remediation.

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.

Enzyme assays and toxicity of pig abattoir waste in Eisenia andrei

Due to high global demand, large amounts of abbattoir waste are generated from pork production. Mismanagement of abattoir waste on agricultural lands can result in soil and water contamination with pathogens and contaminants like metals and nutrients. Therefore, possible effects on soil organisms prior to application should be evaluated. Thus, the aim of this study was to determine the effects of fresh pig abattoir waste (PAWf) and waste after stabilization processes on E. andrei through tests of avoidance behavior, acute toxicity and chronic toxicity. In order to do this, the waste was evaluated fresh (i.e., non-treated), and after aerated composting (PAWa), natural composting (PAWn) and vermicomposting (PAWv). In addition, we used a natural soil with no history of agricultural use as control soil. The evaluation was based on avoidance behavior, mortality, initial and final earthworm weight, and reproduction, in addition to a set of enzyme assays formed by acetylcholinesterase, lipid peroxidation, catalase and glutathione S-transferase measured over time. The ecotoxicological results showed that PAWf and PAWa increased AChE activity at different experimental periods, while PAWn decreased activity at 14 days compared to the control. PAWf and PAWa increased TBARS levels at 7 and 14 days, respectively. CAT activity decreased at 3, 7 and 14 days in PAWv, while GST activity increased at 3 days in PAWa and at 3 and 14 days in PAWf compared to the control. In the acute toxicity test, PAWa and PAWn had a toxic effect on E. andrei, resulting in 100% mortality at 14 days of exposure. Based on our findings, pig abattoir waste should undergo vermicomposting prior to agricultural application to soils.

Evaluation of the effectiveness of a bioremediation process in experimental soils polluted with chromium and lindane

Bioremediation using actinobacterium consortia proved to be a promising alternative for the purification of co-contaminated environments. In this sense, the quadruple consortium composed of Streptomyces sp. M7, MC1, A5, and Amycolatopsis tucumanensis AB0 has been able to remove significant levels of Cr(VI) and lindane from anthropogenically contaminated soils. However, the effectiveness of the bioremediation process could not be evaluated only by analytical monitoring, which is complex mainly due to the characteristics of the matrix, producing non-quantitative analyte recoveries, or interferences in the detection stage and quantification. However, the effectiveness of the bioremediation process cannot be evaluated only through analytical monitoring, which is complex due mainly to the characteristics of the matrix, to the recoveries of non-quantitative analytes or to interferences in the detection and quantification stage. For this reason, it is essential to have tools of ecological relevance to assess the biological impact of pollutants on the environment. In this context, the objective of this work was to establish the appropriate bioassays to evaluate the effectiveness of a bioremediation process of co-contaminated soils. For this, five model species were studied: four plant species (Lactuca sativa, Raphanus sativus, Lycopersicon esculentum, and Zea mays) and one animal species (Eisenia fetida). On plant species, the biomarkers evaluated were inhibition of germination (IG) and the length of hypocotyls/steam and radicles/roots of the seedling. While on E. fetida, mortality (M), weight lost, coelomocyte concentration and cell viability were tested. These bioindicators and the battery of biomarkers quantified in them showed a different level of sensitivity, from maximum to minimum: E. fetida > L. esculentum > L. sativa > R. sativus ≫>Z. mays. Therefore, E. fetida and L. esculentum and their respective biomarkers were selected to evaluate the effectiveness of the bioremediation process due to the capability of assessing the effect on the flora and the fauna of the soil, respectively. The joint application of these bioindicators in a field scale bioremediation process is a feasible tool to demonstrate the recovery of the quality and health of the soil.

Toxic responses of metabolites, organelles and gut microorganisms of Eisenia fetida in a soil with chromium contamination

The toxic sensitivity in different physiological levels of chromium (Cr) contaminated soils with environmentally equivalent concentrations (EEC) was fully unknown. The earthworm Eisenia fetida was exposed to a Cr-contaminated soil at the EEC level (referred to as Cr-CS) to characterize the induced toxicity at the whole body, organ, tissue, subcellular structure and metabolic levels. The results showed that the survival rate, weight and biodiversity of the gut microorganisms (organ) had no significant difference (p > 0.05) between control and Cr-CS groups. Qualitative histopathological and subcellular evaluations from morphology showed earthworms obvious injuries. The organelle injuries combined with the metabolic changes provided additional evidence that the Cr-CS damaged the nucleus and probably disturbed the nucleic acid metabolism of earthworms. 2-hexyl-5-ethyl-3-furansulfonate, dimethylglycine, betaine and scyllo-inositol were sensitive and relatively quantitative metabolites that were recommended as potential biomarkers for Cr-CS based on their significant weights in the multivariate analysis model. In addition, the relative abundance of Burkholderiaceae, Enterobacteriaceae and Microscillaceae of the earthworm guts in the Cr-CS group significantly increased, particularly for Burkholderiaceae (increased by 13.1%), while that of Aeromonadaceae significantly decreased by 5.6% in contrast with the control group. These results provided new insights into our understanding of the toxic effects of the EEC level of Cr contaminated soil from different physiological levels of earthworms and extend our knowledge on the composition and sensitivity of the earthworm gut microbiota in Cr contaminated soil ecosystems. Furthermore, these toxic responses from gut microorganisms to metabolites of earthworms provided important data to improve the adverse outcome pathway and toxic mechanism of the Cr-CS if the earthworm genomics and proteomics would be also gained in the future.

Toxicity of exogenous hexavalent chromium to soil-dwelling springtail Folsomia candida in relation to soil properties and aging time

Chromium (Cr) is a well-known toxic metal, but studies on Cr toxicity to soil-dwelling springtails are fairly limited, and did not consider the effects of various soil properties and long aging time. To address this, the chronic toxicity of Cr(VI) to survival and reproduction of model organism-Folsomia candida were evaluated in the laboratory studies. The results showed that compared to the soils aged only for 2 and 21 d, the concentrations inhibiting 50% reproduction (EC₅₀) significantly increased by 2.8-5.2 fold and 1.7-2.6 fold, the concentrations causing 50% mortality (LC₅₀) were higher than the highest test concentration in four soils aged for 150 d. Furthermore, the aging effects correlated significantly with soil amorphous Fe oxides. The EC₅₀ values of Cr significantly differed in ten soils aged for 150 d, ranging from 27 to 512 mg kg^-1, which were associated with the variations in reduction and sorption capacity in different soils. Regression analysis indicated that soil clay was the most important single factor predicting soil Cr toxicity to reproduction, and the inclusion of cation exchange capacity in the clay regression could best explain the toxicity variance (87.2%). Additionally, soil pH, organic matter and amorphous Fe oxides could also well explain the toxicity variance (>55%).

An uptake and elimination kinetics approach to assess the bioavailability of chromium, copper, and arsenic to earthworms (Eisenia andrei) in contaminated field soils

The aim of this study was to determine the bioavailability of metals in field soils contaminated with chromated copper arsenate (CCA) mixtures. The uptake and elimination kinetics of chromium, copper, and arsenic were assessed in the earthworm Eisenia andrei exposed to soils from a gradient of CCA wood preservative contamination near Hartola, Finland. In soils contaminated with 1480-1590 mg Cr/kg dry soil, 642-791 mg Cu/kg dry soil, and 850-2810 mg Ag/kg dry soil, uptake and elimination kinetics patterns were similar for Cr and Cu. Both metals were rapidly taken up and rapidly excreted by Eisenia andrei with equilibrium reached within 1 day. The metalloid As, however, showed very slow uptake and elimination in the earthworms and body concentrations did not reach equilibrium within 21 days. Bioaccumulation factors (BAF) were low for Cu and Cr (< 0.1), but high for As at 0.54-1.8. The potential risk of CCA exposure for the terrestrial ecosystem therefore is mainly due to As.

Endocrine disruption, oxidative stress and lipometabolic disturbance of Bufo gargarizans embryos exposed to hexavalent chromium

The aim of the current study was to determine the potential developmental and metabolic abnormalities caused by Cr (VI) exposure on Bufo gargarizans (B. gargarizans) embryos. B. gargarizans embryos were treated with different concentrations of Cr (VI) (13, 52, 104, 208, and 416 μg Cr⁶⁺ L^-1) for 6 days. Morphological abnormalities, total length, weight and developmental stage were monitored. Malformations of embryos were also examined using scanning electron microscopy (SEM). In addition, the transcript levels of several genes associated with lipid metabolism, oxidative stress, and thyroid hormones signaling pathways were also determined. Our results showed a time-dependent inhibitory effect of Cr (VI) on the growth and development of B. gargarizans embryos. On day 4, total length, weight, and developmental stage were significantly lower at 416 μg Cr⁶⁺ L^-1 relative to control embryos. On day 6, significant reductions in total length, weight, and developmental stage were observed at 104, 208, and 416 μg Cr⁶⁺ L^-1. Malformed embryos were found in all Cr (VI) treatments, which were characterized by axial flexures, yolk sac edema and rupture, surface tissue hyperplasia, stunted growth, wavy fin and fin flexure. RT-qPCR results showed that exposure to Cr (VI) down-regulated TRβ and Dio2 mRNA expression and up-regulated Dio3 mRNA level at 416 μg Cr⁶⁺ L^-1. The transcript levels of SOD and GPx were upregulated at 52, 208, and 416 μg Cr⁶⁺ L^-1, while the transcript level of HSP90 was downregulated at 52, 208, and 416 μg Cr⁶⁺ L^-1. Also, mRNA expression of lipid synthesis-related genes (FAE and ACC) were significantly downregulated in embryos treated with 208 and 416 μg Cr⁶⁺ L^-1, but mRNA expression of fatty acid β-oxidation-related genes (ACOX, CPT, and SCP) was significantly upregulated at 416 μg Cr⁶⁺ L^-1. Therefore, our results suggested that Cr (VI) could disrupt thyroid endocrine pathways and lipid synthesis, leading to the inhibition of growth and development in B. gargarizans embryos. Furthermore, the decreased ability of scavenging ROS induced by Cr (VI) might be responsible for the teratogenic effects of Cr (VI).

The behaviour of the nematode, Steinernema feltiae (Nematoda: Steinernematidae) in sand contaminated with the industrial pollutant chromium VI

This study set out to determine the suitability of the nematode Steinernema feltiae as a bioindicator for heavy metal pollution, specifically chromium VI. Nematodes were introduced into sand contaminated with concentrations of Cr VI⁺, in a range between 10 and 100 ppm, in increments of 10. Reproductive potential, development times and infectivity vs exposure times to Cr VI were employed as endpoints. It was observed that infective juveniles (IJ) from this nematode can survive and successfully infect host insects in the presence of Cr VI for as much as 13 days, and that the nematode increases its reproductive potential at concentrations up to 100 ppm Cr VI⁺. Conversely, development times (time in days taken for progeny to emerge after larval host death) and IJ infectivity rates were observed to reduce with increasing concentrations of Cr VI. The ability of this nematode to survive in the presence of high concentrations of Cr VI, and its ability to increase progeny numbers at the early stages of Cr VI exposure may provide a survival advantage for this nematode at contaminated sites. It may also demonstrate potential for development as a model species for toxicological assessment in in-situ field sampling.

Immobilization of hexavalent chromium in contaminated soils using biochar supported nanoscale iron sulfide composite

Biochar supported carboxymethyl cellulose (CMC)-stabilized nanoscale iron sulfide (FeS) composite (CMC-FeS@biochar) was prepared and tested for immobilization of hexavalent chromium Cr(VI) in soil. Results of UV-vis and transmission electron microscopy (TEM) showed that the backbone of biochar suppressed the aggregation of FeS, resulting in smaller particle size and more sorption sites than bare FeS. The composite at a dosage of 2.5 mg per gram soil displayed an enhanced Cr(VI) immobilization efficiency (a 94.7% reduction in the toxicity characteristic leaching procedure (TCLP) based leachability and a 95.6% reduction in the CaCl₂ extraction) compared to plain biochar and bare FeS. Sequential extraction procedure (SEP) and X-ray photoelectron spectroscopy (XPS) analysis suggested that CMC-FeS@biochar promoted the conversion of more accessible Cr (exchangeable and carbonate-bound fractions) into the less accessible forms (iron-manganese oxides-bound, organic material-bound, and residual fractions) to reduce the toxicity of Cr(VI) and that surface sorption and reduction were dominant mechanisms for Cr(VI) immobilization. CMC-FeS@biochar greatly reduced the bioavailability of Cr(VI) to wheat and earthworms (Eisenia fetida). Moreover, the application of CMC-FeS@biochar enhanced soil organic matter content and microbial activity. This work highlighted the potential of CMC-FeS@biochar composite as a low-cost, "green", and effective amendment for immobilizing Cr(VI) in contaminated soils and improving soil properties.

The influence of chemical protection on the content of heavy metals in wheat (Triticum aestivum L.) growing on the soil enriched with granular sludge

The presence of heavy metals in Triticum aestivum L. growing on the soil enriched with granular sludge after chemical protection was observed. The five variants of treatments using herbicide (Chwastox Turbo 340SL) and four fungicides (Topsin M 500SC, Amistar 250SC, Artea 330EC, and Falcon 460EC) were performed. On control and experimental plots, the concentration of Ni, Pb, Cr, and Cu in wheat leaves were in the range 0.32-0.99, 0.92-1.57, 0.89-6.31, and 7.08-12.59 mg/kg and in grains 0.03 to 0.11, 0.14-0.25, 0.11-0.76, and 1.06-1.46 mg/kg, respectively. The concentration of Pb in grain protected by MCPA and 2,4-D with thiophanate-methyl and azoxystrobin was higher than the maximum levels of 0.20 mg/kg D.M. The bioconcentration factor (BCF) differed and depended on chemical protection. The highest value of BCF was achieved for Cd. The statistical analysis showed a significant correlation between concentration of metals and quality parameters of wheat. One observed significant negative correlations between Ni/Zeleny sedimentation value (r = -0.51) and between Pb/starch content (r = -0.57). Positive correlations were observed between Cd/yield, the number of grains/ergosterol concentration (respectively, r = 0.41, r = 0.55, r = 0.56), and Zn/thousand grain weight (r = 0.50) at a p ≤ 0.05.

Mode of action of Cr(VI) in immunocytes of earthworms: Implications for animal health

Chromium (Cr) is one of the major and most detrimental pollutant, widely present in the environment as a result of several anthropogenic activities. In mammalian cells, Cr(VI) is known to enhance reactive oxygen species (ROS) production and to cause toxic and genotoxic effects. Less commonly investigated are the effects and mode of action of this contaminant in invertebrates, particularly in soil organisms. In this work, earthworms of the species Eisenia andrei were exposed for 1 and 3 days to various sublethal concentrations of Cr(VI) (2, 15, 30µgmL^-1) using the paper contact toxicity test. In amoeboid leukocytes we investigated intracellular ROS and lipoperoxide production, oxidative DNA damage, and the effects on different cell functions. The analysis of the results shows that Cr(VI) triggered severe adverse reactions; the first events were an increase of intracellular ROS levels, generating in the cells oxidative stress conditions leading to membrane lipid peroxidation and oxidative DNA damage. Lysosomes showed relevant changes such as a strong membrane destabilization, which was accompanied by an increased catabolism of cytoplasmic proteins and accumulation of lipofuscin. With an increase in the dose and/or time of exposure, the physiological status of intracellular organelles (such as lysosomes, nucleus and mitochondria) showed further impairment and amoebocyte immune functions were adversely affected, as shown by the decrease of the phagocytic activity. By mapping the responses of the different parameters evaluated, diagnostic of (oxidative) stress events, against lysosomal membrane stability, a "health status" indicator (able to describe the stress syndrome from its early phase to pathology), we have shown that this biomarker is suitable as a prognostic test for health of earthworms. This is viewed as a crucial step toward the derivation of explanatory frameworks for prediction of pollutant impact on animal health.

Impact of wastewater derived dissolved organic carbon on reduction, mobility, and bioavailability of As(V) and Cr(VI) in contaminated soils

In this work, the effects of various wastewater sources (storm water, sewage effluent, piggery effluent, and dairy effluent) on the reduction, and subsequent mobility and bioavailability of arsenate [As(V)] and chromate [Cr(VI)] were compared using both spiked and field contaminated soils. Wastewater addition to soil can increase the supply of carbon, nutrients, and stimulation of microorganisms which are considered to be important factors enhancing the reduction of metal(loid)s including As and Cr. The wastewater-induced mobility and bioavailability of As(V) and Cr(VI) were examined using leaching, earthworm, and soil microbial activity tests. The rate of reduction of As(V) was much less than that of Cr(VI) both in the presence and absence of wastewater addition. Wastewater addition increased the reduction of both As(V) and Cr(VI) compared to the control (Milli-Q water) and the effect was more pronounced in the case of Cr(VI). The leaching experiment indicated that Cr(VI) was more mobile than As(V). Wastewater addition increased the mobility and bioavailability of As(V), but had an opposite effect on Cr(VI). The difference in the mobility and bioavailability of Cr(VI) and As(V) between wastewater sources can be attributed to the difference in their dissolved organic carbon (DOC) content. The DOC provides carbon as an electron donor for the reduction of As(V) and Cr(VI) and also serves as a complexing agent thereby impacting their mobility and bioavailability. The DOC-induced reduction increased both the mobility and bioavailability of As, but it caused an opposite effect in the case of Cr.

Comparison of chromium III and VI toxicities in water using sulfur-oxidizing bacterial bioassays

The toxicities of Cr (III) and Cr (VI) in water were evaluated using sulfur-oxidizing bacterial (SOB) bioassays both in batch and fed-batch conditions. Two days were enough for a quick buildup of SOB consortium in the master culture reactor (MCR). At concentrations up to 100 mg L(-1), Cr (III) was found to be nontoxic in both conditions, while Cr (VI) at very low concentrations (0.1-2 mg L(-1)) was very toxic to the SOB. Literature review suggested that the nontoxic nature of Cr (III) might be due to the absence of the iron uptake pathway in Acidithiobacillus caldus (the predominant bacteria in our reactors), which is required for Cr (III) uptake. The 2-h median effective concentration (EC50) values obtained for Cr (VI) in the batch and fed-batch tests were 2.7 mg L(-1) and 1.5 mg L(-1), respectively.

Lethal and sub-lethal effects on the Asian common toad Duttaphrynus melanostictus from exposure to hexavalent chromium

Chromium discharged in industrial effluents frequently occurs as an environmental pollutant, but the lethal and sub-lethal effects the heavy metal might cause in animals exposed to it have been insufficiently investigated. Selecting the amphibian Duttaphrynus melanostictus, we carried out laboratory tests to investigate the effects of short and long term exposure to hexavalent chromium (Cr(VI)) in both tadpoles and adult toads. The concentrations used were 0.002, 0.02, 0.2, 1.0 and 2.0mg/L, the first three corresponding to field levels. In vitro exposures were also carried out using toad erythrocytes and Cr(VI) concentrations of 0.0015, 0.003, 0.015, 0.03, 0.15mg/L. Mortality, growth retardation, developmental delays and structural aberrations were noted in the metal-treated tadpoles, with increasing incidence corresponding to increase in Cr(VI) level and duration of exposure. Many of the sub-lethal effects were evident with long term exposure to environmentally relevant levels of the toxicant. Changes in selected blood parameters and erythrocyte morphometry were also detected in Cr(VI) exposed toads, indicating anaemic and leucopenic conditions. In the genotoxicity study, DNA damage indicated by comet assay and increased micronuclei frequency, occurred at the low Cr(VI) concentrations tested. The multiple deleterious effects of exposure to chromium signal the need for monitoring and controlling the discharge of chromium to the environment. The dose-dependency and genotoxic effects observed in this widely distributed Asian toad indicates its suitability for monitoring heavy metal pollution in aquatic systems.

Differential effect of biochar upon reduction-induced mobility and bioavailability of arsenate and chromate

Heavy metals such as chromium (Cr) and arsenic (As) occur in ionic form in soil, with chromate [Cr(VI)] and arsenate As(V) being the most pre-dominant forms. The application of biochar to Cr(VI) and As(V) spiked and field contaminated soils was evaluated on the reduction processes [(Cr(VI) to Cr(III)] and [As(V) to As(III))], and subsequent mobility and bioavailability of both As(V) and Cr(VI). The assays used in this study included leaching, soil microbial activity and XPS techniques. The reduction rate of As(V) was lower than that of Cr(VI) with and without biochar addition, however, supplementation with biochar enhanced the reduction process of As(V). Leaching experiments indicated Cr(VI) was more mobile than As(V). Addition of biochar reversed the effect by reducing the mobility of Cr and increasing that of As. The presence of Cr and As in both spiked and contaminated soils reduced microbial activity, but with the addition of biochar to these soils, the microbial activity increased in the Cr(VI) contaminated soils, while it was further decreased with As(V) contaminated soils. The addition of biochar was effective in mitigating Cr toxicity by reducing Cr(VI) to Cr(III). In contrast, the conversion process of As(V) to As(III) hastened by biochar was not favourable, as As(III) is more toxic in soils. Overall, the presence of functional groups on biochar promotes reduction by providing the electrons required for reduction processes to occur as determined by XPS data.

Tracing potential soil contamination in the historical Solvay soda ash plant area, Jaworzno, Southern Poland

This study of soil conditions was carried out on 30 meadow soil (podzol) samples from the vicinity of the soda ash heap in Jaworzno, supplemented by analyses of 18 samples of waste deposited on the heap. In all samples, the total content of macroelements (Ca and Na) and heavy metals (Cd, Cr, Ni, Pb and Zn) as well as pH were analysed. The element concentrations were measured using inductively coupled plasma optical emission spectrometry (ICP-OES). The materials examined were neutral to ultra-alkaline. Total accumulations (mg kg(-1)) of chemical elements in the soil vary from 130.24 to 14076.67 for Ca, 41.40-926.23 for Na, 0.03-3.34 for Cd, 0.94-103.62 for Cr, 0.94-35.89 for Ni, 3.51-76.47 for Pb and 12.05-279.13 for Zn, whereas quantities of the same elements in the waste samples vary from 171705.13 to 360487.94 for Ca, 517.64-3152.82 for Na, 0.2-9.89 for Cd, 1.16-20.40 for Cr, 1.08-9.79 for Ni, 0.1-146.05 for Pb and 10.26-552.35 for Zn. The vertical distribution of the metals was determined in each soil profile. Despite enrichment of heavy metals in the uppermost horizon on the top of the heap, the results lead to the conclusion that the relation of historical production of soda ash in Jaworzno to current contamination of the local soil environment is insignificant.

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.

Histological Alterations in the Body Wall of the Tropical Earthworm Eudrilus eugeniae Exposed to Hexavalent Chromium

The tropical earthworm Eudrilus eugeniae was chronically exposed to hexavalent chromium (Cr) in its substrate over a concentration range from 0.24 to 893 mg kg(-1). Histological alterations in the body wall epithelium included cell fusion, reduction in thickness of the epithelial layer, a marked increase in pyknotic nuclei and epithelial sloughing. Similar changes were noted in the circular and longitudinal muscles with damage being indicated by the prominent inter-muscular cell spaces and disintegration. Many of these noted alterations intensified with increasing levels of exposure. It is significant that some of the changes recorded here were evident even at the lowest concentration of 0.24 mg kg(-1), an environmentally relevant concentration. Hence, the observed trends could be taken as an early warning to the imminent threats of heavy metal pollution to epigeic earthworm species.

Development of a multi-species biotic ligand model predicting the toxicity of trivalent chromium to barley root elongation in solution culture

Little knowledge is available about the influence of cation competition and metal speciation on trivalent chromium (Cr(III)) toxicity. In the present study, the effects of pH and selected cations on the toxicity of trivalent chromium (Cr(III)) to barley (Hordeum vulgare) root elongation were investigated to develop an appropriate biotic ligand model (BLM). Results showed that the toxicity of Cr(III) decreased with increasing activity of Ca²⁺ and Mg²⁺ but not with K⁺ and Na⁺. The effect of pH on Cr(III) toxicity to barley root elongation could be explained by H⁺ competition with Cr³⁺ bound to a biotic ligand (BL) as well as by the concomitant toxicity of CrOH²⁺ in solution culture. Stability constants were obtained for the binding of Cr³⁺, CrOH²⁺, Ca²⁺, Mg²⁺ and H⁺ with binding ligand: log K_CrBL 7.34, log K_CrOHBL 5.35, log K_CaBL 2.64, log K_MgBL 2.98, and log K_HBL 4.74. On the basis of those estimated parameters, a BLM was successfully developed to predict Cr(III) toxicity to barley root elongation as a function of solution characteristics.

Influence of the activity of Allobophora molleri in microbial activity and metal availability of arsenic-polluted soils

We investigate the use of Allolobophora molleri as a biomarker of arsenic (As)-polluted soils and study the influence of A. molleri on the metabolic activity and microbial biodiversity of soil polluted with As. Because there are no experimental data available regarding the effect of the pollutant rate of As on A. molleri, we determined the LC₅₀ that was 143.5 mg As kg(-1). Sodium arsenite was added at two rates, equivalent to 143.5 and 71.8 mg As kg(-1) soil, to a soil that was then maintained with and without worms for 120 days. In addition, a nonpolluted soil without and with earthworms was used as the control. The As concentration in the soil was measured after 7 and 120 and the worm weight and As concentration after 120 days of exposure. Soil enzymatic activities and the structure of the soil microbial community, by analysis of phospholipid fatty acids, were determined. At the end of the experiment, the highest earthworm As contents were found in soils polluted with the highest rate of As. Earthworm weights significantly decreased in soil polluted with 143.5 or 71.8 mg As kg(-1), by 49.9 and 29.8% of initial weight, because the worm consumption rate decreased. These results suggest that A. molleri can be used as a good biomarker of the As toxicity. The As available fraction decreased in polluted soil with worms because the metal was accumulated in worm tissues. However, this assimilation was lower than other worms such as L. rubbellus or L. terrestris. Soil enzymatic activities were decreased in As-polluted soils but were increased significantly by the presence of earthworms. The earthworms modified the soil microbial diversity. In this respect, A. molleri significantly increased (p < 0.05) the bacterial and fungal populations. Soil As pollution decreased microbial biodiversity but to a lesser extent in the presence of A. molleri.

Terrestrial and aquatic ecotoxicity assessment of Cr(VI) by the ReCiPe method calculation (LCIA): application on an old industrial contaminated site

The most stable forms of chromium in the environment are chromium (III) and chromium (VI), the former being relatively immobile and necessary for organisms, and the latter being highly soluble and toxic. It is thus important to characterise ecotoxicological impacts of Cr(VI). However, there are still some important uncertainties in the calculation of ecotoxicological impacts of heavy metals in the LCIA global approach. The aim of this paper is to understand how the spatial and dynamic characterization of life cycle inventory (LCI) data can be exploited in life cycle impact assessment and particularly for the evaluation of the aquatic and terrestrial ecotoxicity of Cr(VI). To quantify these impacts, we studied an industrial waste landfill in the North of France that was contaminated with chromium. On the polluted area, the aquatic contamination is due to the slag heap as well as to chromium spots in soil. The soil contamination is mainly due to infiltration of chromium from the infill. The concentration of Cr(VI) in soil and water varies according to seasonal climatic variations and groundwater level. These variations have an effect on the Cr(VI) fate factor, in particular on transfer and residence time of the substance. This study underlines the spatial distribution of aquatic ecotoxicity and the temporal variation of freshwater ecotoxicity. We analysed the correlation between precipitation, temperature, concentration and ecotoxicity impact. With regards to the terrestrial ecotoxicity, the study focused on the vertical variation of the ecotoxicity and the major role of the soil layer composition into terrestrial pollution.

Selected enzyme activities of urban heavy metal-polluted soils in the presence and absence of an oligochaete, Lampito mauritii (Kinberg)

Soils samples collected from five different areas (S1-S5) around electroplating industries in the city of Coimbatore were analysed for the activities of selected enzymes (cellulase, phosphatase, amylase, urease, and invertase) in the presence and absence of the earthworm Lampito mauritii (Kinberg). Heavy metal analysis of soils showed that chromium (<504 mg/kg) and copper (<28.1mg/kg) contents were much higher than cadmium (<10.60 mg/kg) except in S5, where cadmium (10.6 mg/kg) was higher than the copper. Except for phosphatase, the activities of all enzymes increased with increasing period of incubation under laboratory conditions, both with and without earthworms. The results of the three-way ANOVA (effect of three factors- worms-with and without addition, soil and incubation time), however, showed that there was no significant difference between enzyme activities (with and without earthworm) and soil and incubation time for amylase and urease activity. Further, no significant difference was found between soils for cellulase activity and between all the above factors for urease activity. The results concluded that though the earthworms died at the end of the incubation period, the resultant increase or decrease in the enzymatic activity may be attributed to the metabolic activities of the worms during their lifetime in the experimental container. Also, the worms after death may have provided suitable substrate for the growth of the microorganisms thereby influencing enzyme activity.

Genotoxic effects of nickel, trivalent and hexavalent chromium on the Eisenia fetida earthworm

The aim of this study was to examine genotoxic effects of nickel (Ni=105 mg kg(-1)), trivalent and hexavalent chromium (Cr=491 mg kg(-1)) on the Eisenia fetida earthworm after 2 and 4d of exposure to two different spiked soils (an artificial (OECD) and a natural one). DNA damages were evaluated on the earthworm's coelomocytes using the comet assay. After an exposure into OECD spiked soils, Ni did not induce genotoxic effect whereas Cr(III) and Cr(VI) revealed to be genotoxic after 2d of exposure. After 4d of exposure, only Cr(VI) still induced significant damages. In natural spiked soils, nickel and Cr(III) revealed to be genotoxic after 2 and 4d of exposure. Concerning Cr(VI) toxicity, all the earthworms died after 1d of exposure. These results underline the importance to take into account the nature and the speciation of metallic pollutants, although the experiment has been performed on spiked soil with higher bioavailibity than in contaminated natural soil.

The use of Collembola avoidance tests to characterize sewage sludges as soil amendments

The ecotoxicological characterization of sewage sludge takes into account the additive, antagonistic and synergistic effects that occur as a result of multi-chemical interactions. Such an evaluation therefore is essential to complement the chemical analysis that, although required by law, is clearly insufficient. Using a tiered approach in the toxic evaluation of sewage sludge allows for characterization of toxicity in a timely manner. According to the literature, reproduction tests with Folsomia candida are suitable tools for the toxic assessment of organic sludges. Therefore, the inclusion of Collembola avoidance tests at a screening level (low tier), and acting as a trigger for longer-period tests (high tier; e.g. reproduction test), may provide a successful strategy, and may complement the currently proposed test battery. To evaluate the use of both avoidance and reproduction tests with collembolans in such a tiered approach, three sewage sludges (urban, olive and electroplating industries) were mixed in with a field-collected soil at different concentrations. Avoidance and reproduction tests were performed with the soil-sludge mixtures after 0, 4 and 12 weeks of incubation. The tests detected no toxicity in soil-sludge mixtures of urban and olive sludges at any incubation period. Mixtures with sludge from the electroplating industry induced toxicity only in the avoidance tests with freshly prepared and 4-week incubated samples. These results demonstrate the ability of Collembola avoidance tests to assess sewage sludge toxicity over time and its potential for hazardous sludge characterization at low tier levels.

Developmental toxicity, uptake and distribution of sodium chromate assayed by frog embryo teratogenesis assay-Xenopus(FETAX)

The embryotoxicity and teratogenicity of Cr(VI) on the survival and morphology of the anuran Xenopus laevis have been assessed by frog embryo teratogenesis assay-Xenopus (FETAX). The lethal median (LC(50)) and teratogenic median (TC(50)) concentration values of Cr(VI) were 890 microM and 260 microM, respectively. The calculated teratogenic index (TI) value was 3.42, suggesting that hexavalent chromium has a teratogenic potential. Malformations of embryos included lifting of the body, coiling of the tail and body oedema. Furthermore, the chromium salt caused significant growth retardation at 25 microM exposure concentrations. The use of radiolabelled (51)Cr(VI) allowed the determination of the time course uptake of Cr in Xenopus exposed to concentrations ranging from 0.025 to 500 microM. The evaluation of its distribution into the body (head-abdomen-tail) was evaluated at different exposure times. Chromium is taken up at 24 h by Xenopus embryos for all concentrations tested. At 48 h post fertilization (stage of larva) the amount of Cr accumulated by the two-day-old larva ranged from 0.42 to 580 pg mg(-1) wet weight at 0.025 and 500 microM respectively. These amounts were lower than those at 24 h (2.77 to 11016 pg mg(-1) wet weight embryo) reaching values of the same order of magnitude at 120 h (five-days-old larva). Since at 48 h Xenopus development leads to a swimming embryo, the observed uptake at 24 h could be the result of the binding of Cr to jelly coat compounds surrounding the embryo body as confirmed by gel filtration experiments on (51)Cr-jelly coat. The interaction of Cr with jelly coat is in agreement with the role of jelly coat in protecting the embryo against pathogen and chemical toxins to ensure fertilization. This work further supports the hypothesis that Cr contamination of surface waters could contribute to explain the reported worldwide depletion of frog population.

The effects of chromium VI on the fitness and on the beta-tubulin genes during in vivo development of the nematode Steinernema feltiae

The entomopathogenic nematode (EPN), Steinernema feltiae, is a commonly occurring nematode in the soil in Ireland. Consequently, we have conducted investigations as to the utility of this species as a candidate organism for the detection of chromium in Irish soils. These experiments have demonstrated that S. feltiae can survive and reproduce in the presence of high concentrations of chromium VI. It was observed that concentrations as high as 1000 ppm have little effect on the ability of this organism to produce large numbers of progeny. Nematodes were not observed to reproduce above 1800 ppm. However, an increase in development times for the nematode in vivo was noted at concentrations of 400 ppm upwards. This paper also illustrates the effects upon the beta-tubulin genes within nematode populations exposed to chromium VI in vivo. DNA sequencing has shown that elevated levels of variations occur among the population treatments, although these variations do not appear to be dependent upon chromium concentration. These findings constitute this organism appropriate for further investigation for the development of sub-lethal end points and biomarkers for the detection and biomonitoring of chromium VI contamination in soil.

Growth and reproduction of the earthworm Eisenia fetida after exposure to leachate from wood preservatives

Wood preserved with chromated copper arsenate (CCA) and alkaline copper quaternary (ACQ) was mixed with artificial rainwater, to generate leachates containing As, Cr and Cu. Then, leachates were applied to two soils at rates of 13-169 mg As kg(-1) soil (dry weight basis), 12-151 mg Cr kg(-1) and 10-216 mg Cu kg(-1). Metal bioavailability was evaluated after 28 days using the earthworm Eisenia fetida (Savigny). Metal concentrations in earthworm tissue ranged from negligible to 80 mg As kg(-1) (dry weight basis), 89 mg Cr kg(-1) and 90 mg Cu kg(-1), which appeared to be non-lethal to E. fetida. There was less Cu available to earthworms in the Courval soil (pH 7.8) than the Châteauguay soil (pH 6.8), but earthworm growth and reproduction were not affected by exposure to Cu from ACQ-treated wood. In contrast, earthworms exposed to As, Cr and Cu from the CCA-treated wood gained weight more quickly in the Courval soil (1.3-21 mg g(-1) initial biomass days) than in the Châteauguay soil (0.2-7.8 mg g(-1) day(-1)), but fewer than 20% of the cocoons deposited by the faster-growing earthworms hatched by the end of the 56 days ecotoxicology test. It appeared that E. fetida can allocate more energy to growth than reproduction, delaying cocoon development and hatching in some situations. Further information is needed on the soil factors that may induce such behavior, as it can affect the interpretation of results from the earthworm ecotoxicology test.

In vitro and in vivo genotoxicity assessment of Cr(VI) using comet assay in earthworm coelomocytes

Hexavalent chromium is the major terrestrial pollutant released from electroplating industries, tanneries, thermal power plants and sewage. Cr(VI) is reported genotoxicant in vertebrates. Sub-lethal level of Cr(VI) can cause DNA damage. Earthworms are ecologically important soil invertebrates, used for ecotoxicological studies. In present study coelomocytes of Dichogaster curgensis were used for assessing Cr(VI) genotoxicity using single cell gel electrophoresis [(SCGE) i.e. comet assay] following in vitro and in vivo exposures. Cr(VI) produces reactive oxygen species (ROS) in the cellular system, which can be a major cause of DNA damage. Dose dependent DNA damage was observed during in vitro exposure, while in vivo exposure showed increasing DNA damage till 30ppm in terms of arbitrary units and unexpected decrease in arbitrary units at 70 and 100ppm of Cr(VI). It is speculated that the decrease in arbitrary units at higher concentrations might be due to lower DNA mobility, caused by formation of different types of cross-links.