Integration of toxicological and chemical tools to assess the bioavailability of metals and energetic compounds in contaminated soils

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

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

Effects of Electronic and Electrical Waste-Contaminated Soils on Growth and Reproduction of Earthworm (Alma nilotica)

Informal recycling of electronic waste (e-waste) contaminates local environments with metals and other organic compounds. The adverse effects on native earthworm populations are poorly understood. The objective of the present study was to determine metal concentrations in soils from e-waste activity sites in Douala (Cameroon) and assess the effects of these soils on the growth and reproduction of the local earthworm, Alma nilotica. Concentrations of nine metals (arsenic [As], cadmium [Cd], cobalt [Co], chromium [Cr], copper [Cu], mercury [Hg], nickel [Ni], lead [Pb], and zinc [Zn]) were measured in soil samples collected from eight e-waste activity and two non-e-waste sites. Earthworms were then exposed to these soils in the laboratory following test guidelines of the Organisation for Economic Co-operation and Development. Metal concentrations in the e-waste-contaminated soils were significantly higher than in the non-e-waste soils. The e-waste soils were found to have a different soil metal profile (Cu > Pb > Zn > Cr > Ni > Co > As > Cd > Hg) from that of the non-e-waste soils (Zn > Cr > Cu > Pb > Ni > As > Cd > Co > Hg). Earthworm growth and reproduction were significantly inhibited in organisms exposed to soils from e-waste sites. Reproduction was particularly affected, with a mean of 8 ± 5.6 offspring/10 worms in the e-waste-exposed worm groups compared with 90.5 ± 0.7 in non-e-waste soil worms. Notably, earthworm growth recovered during depuration in clean soil, indicating the possibility of remediation activities. The results demonstrate that soils at e-waste sites can affect the health of resident worm populations, which may be more sensitive than temperate species. They also highlight the potential of a bioassay-based approach in monitoring risks at e-waste sites. Environ Toxicol Chem 2022;41:287-297. © 2021 SETAC.

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

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

Acute and chronic toxicity of the fungicide carbendazim to the earthworm Eisenia fetida under tropical versus temperate laboratory conditions

Research efforts into the potential side-effects of pesticides on beneficial organisms have focused on temperate test species and conditions. There is thus a need for studies into the ecotoxicity of a vaster range of pesticides under tropical conditions. The present study therefore aimed to compare the acute and chronic toxicity of the fungicide carbendazim to the earthworm Eisenia fetida under tropical and temperate conditions. To this end, laboratory toxicity tests were conducted with a tropical and European strain of E. fetida, using different artificial (OECD and TAS) and natural (LUFA and TNS) soils, and under different test temperatures (20 °C and 28 °C). In the acute lethality tests with artificial soils, the tropical strain of E. fetida was three to four order of magnitude less sensitive than the European strain, which is ascribed to the higher test temperature and (hence) higher microbial activity/pesticide degradation. The tropical strain was particularly sensitive in the tropical natural soil, which was attributed to the low pH (3.9) of this soil. The chronic toxicity tests overall also showed a lower sensitivity of the tropical strain on reproduction. These findings thus support the use of toxicity data generated under temperate conditions in tropical pesticide effect assessments. However, intensive agricultural practices in the tropics may dictate that exposure levels (and hence potentially also risks) are higher.

Distribution of heavy metals in crop soils from an agricultural region of the Yucatan Peninsula and biochemical changes in earthworm Eisenia foetida exposed experimentally

Heavy metals (HM) are natural components of agricultural soils. However, excessive use of agrochemicals (fertilizers and pesticides) can increase the concentration of these elements, making them harmful to crops and soil biota. Therefore, this study aimed to evaluate the concentrations of 6 HM (Cr, Mn, Cu, Zn, Al, and Fe) in soils collected from a typical agricultural region of the Yucatan Peninsula, Mexico, and relate their effects on weight, biotransformation (EROD, GST), and oxidative stress (SOD, CAT, LPO, and MT) in the earthworm Eisenia foetida. The results showed different concentrations of HM accumulation in soils, in the following order, Fe (598.74 ± 223.81 μg g^-1), Al (145.30 ± 33.54 μg g^-1), Cr (88.38 ± 36.23 μg g^-1), Mn (69.53 ± 22.48 μg g^-1), Zn (54.10 ± 12.04 μg g^-1), and Cu (24.91 ± 12.40 μg g^-1), the soils with maize, soybean, and chihua squash crops being the ones with the highest distribution and availability of these elements. These concentrations of metals did not produce mortality. However, Cr, Fe, and Al induced a significant biomass loss of E. foetida. The integrated biomarker response version 2 revealed that soil with maize cultivation was affected the most, with the earthworms exposed to this soil showing greater variations in the dominant biological responses including EROD, TBARS, SOD, and MT (IBRv2 = 9.73). PCA analysis indicated a strong positive relationship between these oxidative stress biomarkers and Cu and Zn concentrations. These findings provide a reference guide that should be part of the monitoring and management programs for different agricultural types in the region under study.

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

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

Assessing bioavailability of complex chemical mixtures in contaminated soils: Progress made and research needs

Understanding the distribution, behaviour and interactions of complex chemical mixtures is key for providing the evidence necessary to make informed decisions and implement robust remediation strategies. Much of the current risk assessment frameworks applied to manage land contamination are based on total contaminant concentrations and the exposure assessments embedded within them do not explicitly address the partitioning and bioavailability of chemical mixtures. These oversights may contribute to an overestimation of both the eco-toxicological effects of the fractions and the mobility of contaminants. In turn, this may limit the efficacy of risk frameworks to inform targeted and proportionate remediation strategies. In this review we analyse the science surrounding bioavailability, its regulatory inclusion and the challenges of incorporating bioavailability in decision making process. While a number of physical and chemical techniques have proven to be valuable tools for estimating bioavailability of organic and inorganic contaminants in soils, doubts have been cast on its implementation into risk management soil frameworks mainly due to a general disagreement on the interchangeable use of bioavailability and bioaccessibility, and the associated methods which are still not standardised. This review focuses on the role of biotic and abiotic factors affecting bioavailability along with soil physicochemical properties and contaminant composition. We also included advantages and disadvantages of different extraction techniques and their implications for bioavailability quantitative estimation. In order to move forward the integration of bioavailability into site-specific risk assessments we should (1) account for soil and contaminant physicochemical characteristics and their effect on bioavailability; (2) evaluate receptor's potential exposure and uptake based on mild-extraction; (3) adopt a combined approach where chemical-techniques are used along with biological methods; (4) consider a simplified and cost-effective methodology to apply at regulatory and industry setting; (5) use single-contaminant exposure assessments to inform and predict complex chemical mixture behaviour and bioavailability.

Bioavailability and chronic toxicity of bismuth citrate to earthworm Eisenia andrei exposed to natural sandy soil

The present study describes bioavailability and chronic effects of bismuth to earthworms Eisenia andrei using OECD reproduction test. Adult earthworms were exposed to natural sandy soil contaminated artificially by bismuth citrate. Average total concentrations of bismuth in soil recovered by HNO₃ digestion ranged from 75 to 289mg/kg. Results indicate that bismuth decreased significantly all reproduction parameters of Eisenia andrei at concentrations ≥ 116mg/kg. However, number of hatched cocoons and number of juveniles seem to be more sensitive than total number of cocoons, as determined by IC₅₀; i.e., 182, 123 and > 289mg/kg, respectively. Bismuth did not affect Eisenia andrei growth and survival, and had little effect on phagocytic efficiency of coelomocytes. The low immunotoxicity effect might be explained by the involvement of other mechanisms i.e. bismuth sequestered by metal-binding compounds. After 28 days of exposure bismuth concentrations in earthworms tissue increased with increasing bismuth concentrations in soil reaching a stationary state of 21.37mg/kg dry tissue for 243mg Bi/kg dry soil total content. Data indicate also that after 56 days of incubation the average fractions of bismuth available extracted by KNO₃ aqueous solution in soil without earthworms varied from 0.0051 to 0.0229mg/kg, while in soil with earthworms bismuth concentration ranged between 0.310-1.347mg/kg dry soil. We presume that mucus and chelating agents produced by earthworms and by soil or/and earthworm gut microorganisms could explain this enhancement, as well as the role of dermal and ingestion routes of earthworms uptake to soil contaminant.

Bioconcentration factors and plant-water partition coefficients of munitions compounds in barley

Plants growing in the soils at military ranges and surrounding locations are exposed, and potentially able to uptake, munitions compounds (MCs). The extent to which a compound is transferred from the environment into organisms such as plants, referred to as bioconcentration, is conventionally measured through uptake experiments with field/synthetic soils. Multiple components/phases that vary among different soil types and affect the bioavailability of the MC, however, hinder the ability to separate the effects of soil characteristics from the MC chemical properties on the resulting plant bioconcentration. To circumvent the problem, this work presents a protocol to measure steady state bioconcentration factors (BCFs) for MCs in barley (Hordeum vulgare L.) using inert laboratory sand rather than field/synthetic soils. Three MCs: 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), and 2,4-dinitroanisole (2,4-DNAN), and two munition-like compounds (MLCs): 4-nitroanisole (4-NAN) and 2-methoxy-5-nitropyridine (2-M-5-NPYNE) were evaluated. Approximately constant plant biomass and exposure concentrations were achieved within a one-month period that produced steady state log BCF values: 0.62 ± 0.02, 0.70 ± 0.03, 1.30 ± 0.06, 0.52 ± 0.03, and 0.40 ± 0.05 L kg_{plant dwt}^-1 for TNT, 2,4-DNT, 2,4-DNAN, 4-NAN, and 2-M-5-NPYNE, respectively. Furthermore, results suggest that the upper-bounds of the BCFs can be estimated within an order of magnitude by measuring the partitioning of the compounds between barley biomass and water. This highlights the importance of partition equilibrium as a mechanism for the uptake of MCs and MLCs by barley from interstitial water. The results from this work provide chemically meaningful data for prediction models able to estimate the bioconcentration of these contaminants in plants.

Estimating Grass-Soil Bioconcentration of Munitions Compounds from Molecular Structure

A partitioning-based model is presented to estimate the bioconcentration of five munitions compounds and two munition-like compounds in grasses. The model uses polyparameter linear free energy relationships (pp-LFERs) to estimate the partition coefficients between soil organic carbon and interstitial water and between interstitial water and the plant cuticle, a lipid-like plant component. Inputs for the pp-LFERs are a set of numerical descriptors computed from molecular structure only that characterize the molecular properties that determine the interaction with soil organic carbon, interstitial water, and plant cuticle. The model is validated by predicting concentrations measured in the whole plant during independent uptake experiments with a root-mean-square error (log predicted plant concentration-log observed plant concentration) of 0.429. This highlights the dominant role of partitioning between the exposure medium and the plant cuticle in the bioconcentration of these compounds. The pp-LFERs can be used to assess the environmental risk of munitions compounds and munition-like compounds using only their molecular structure as input.

A structural equation model of soil metal bioavailability to earthworms: confronting causal theory and observations using a laboratory exposure to field-contaminated soils

Structural equation models (SEM) are increasingly used in ecology as multivariate analysis that can represent theoretical variables and address complex sets of hypotheses. Here we demonstrate the interest of SEM in ecotoxicology, more precisely to test the three-step concept of metal bioavailability to earthworms. The SEM modeled the three-step causal chain between environmental availability, environmental bioavailability and toxicological bioavailability. In the model, each step is an unmeasured (latent) variable reflected by several observed variables. In an exposure experiment designed specifically to test this SEM for Cd, Pb and Zn, Aporrectodea caliginosa was exposed to 31 agricultural field-contaminated soils. Chemical and biological measurements used included CaC12-extractable metal concentrations in soils, free ion concentration in soil solution as predicted by a geochemical model, dissolved metal concentration as predicted by a semi-mechanistic model, internal metal concentrations in total earthworms and in subcellular fractions, and several biomarkers. The observations verified the causal definition of Cd and Pb bioavailability in the SEM, but not for Zn. Several indicators consistently reflected the hypothetical causal definition and could thus be pertinent measurements of Cd and Pb bioavailability to earthworm in field-contaminated soils. SEM highlights that the metals present in the soil solution and easily extractable are not the main source of available metals for earthworms. This study further highlights SEM as a powerful tool that can handle natural ecosystem complexity, thus participating to the paradigm change in ecotoxicology from a bottom-up to a top-down approach.

Combined subacute toxicity of copper and antiparasitic albendazole to the earthworm (Eisenia fetida)

Copper (Cu) is one of the most common metal contaminants, and albendazole (ABZ) is a veterinary drug with a high efficacy against helminthes. It is believed that the two may co-exist in soil. In this study, the combined subacute toxicity of Cu exposure (0, 80, 120, 160 mg kg(-1)) and ABZ exposure (0, 3, 9 mg kg(-1)) in earthworms (Eisenia fetida) were observed using three approaches, namely chronic growth and reproduction, antioxidant enzyme activity, and earthworm Cu residue. The results have shown that the toxicity of Cu on cocoon hatching success and biomass was alleviated by presence of low concentrations of ABZ (3 mg kg(-1)) during a 56-day exposure period. However, the sensitivity of the earthworms' reproduction to Cu increased with the presence of high concentrations of ABZ (9 mg kg(-1)), indicating a reduction beginning at a Cu concentration of 80 mg kg(-1), in the cocoon number, hatching success, and biomass. In addition, the three enzyme activities exhibited different responsive patterns, indicating inducement in the catalase and glutathione peroxidase, and inhibition in the superoxide dismutase, which were dependent on the exposure times and concentrations. In regard to the earthworm Cu residue, when increasing Cu exposure concentrations, the internal Cu concentrations tended to level off, exhibited a linear pattern at the Cu concentration range of 40 to 120 mg kg(-1), and showed a stable trend above 120 mg kg(-1). The results of the present study can potentially provide important information regarding the combined toxicity of the veterinary drugs and the heavy metals in soil.

Antioxidant responses of Annelids, Brassicaceae and Fabaceae to pollutants: a review

Pollutants, such as Metal Trace Elements (MTEs) and organic compounds (polycyclic aromatic hydrocarbons, pesticides), can impact DNA structure of living organisms and thus generate damage. For instance, cadmium is a well-known genotoxic and mechanisms explaining its clastogenicity are mainly indirect: inhibition of DNA repair mechanisms and/or induction of Reactive Oxygen Species (ROS). Animal or vegetal cells use antioxidant defense systems to protect themselves against ROS produced during oxidative stress. Because tolerance of organisms depends, at least partially, on their ability to cope with ROS, the mechanisms of production and management of ROS were investigated a lot in Ecotoxicology as markers of biotic and abiotic stress. This was mainly done through the measurement of enzyme activities The present Review focuses on 3 test species living in close contact with soil that are often used in soil ecotoxicology: the worm Eisenia fetida, and two plant species, Trifolium repens (white clover) and Brassica oleracea (cabbage). E. fetida is a soil-dwelling organism commonly used for biomonitoring. T. repens is a symbiotic plant species which forms root nodule with soil bacteria, while B. oleracea is a non-symbiotic plant. In literature, some oxidative stress enzyme activities have already been measured in those species but such analyses do not allow distinction between individual enzyme involvements in oxidative stress. Gene expression studies would allow this distinction at the transcriptomic level. A literature review and a data search in molecular database were carried out on the basis of keywords in Scopus, in PubMed and in Genbank™ for each species. Molecular data regarding E. fetida were already available in databases, but a lack of data regarding oxidative stress related genes was observed for T. repens and B. oleracea. By exploiting the conservation observed between species and using molecular biology techniques, we partially cloned missing candidates involved in oxidative stress and in metal detoxification in E. fetida, T. repens and B. oleracea.

Assessing the ecotoxicological effects of long-term contaminated mine soils on plants and earthworms: relevance of soil (total and available) and body concentrations

The interactions and relevance of the soil (total and available) concentrations, accumulation, and acute toxicity of several essential and non-essential trace elements were investigated to determine their importance in environmental soil assessment. Three plant species (T. aestivum, R. sativum, and V. sativa) and E. fetida were simultaneously exposed for 21 days to long-term contaminated soils collected from the surroundings of an abandoned pyrite mine. The soils presented different levels of As and metals, mainly Zn and Cu, and were tested at different soil concentrations [12.5, 25, 50, and 100% of contaminated soil/soil (w/w)] to increase the range of total and available soil concentrations necessary for the study. The total concentrations in the soils (of both As and metals) were better predictors of earthworm uptake than were the available concentrations. In plants, the accumulation of metals was related to the available concentrations of Zn and Cu, which could indicate that plants and earthworms accumulate elements from different pools of soil contaminants. Moreover, Zn and Cu, which are essential elements, showed controlled uptake at low concentrations. The external metal concentrations predicted earthworm mortality, whereas in plants, the effects on growth were correlated to the As and metal contents in the plants. In general, the bioaccumulation factors were lower at higher exposure levels, which implies the existence of auto-regulation in the uptake of both essential and non-essential elements by plants and earthworms.

Effects of cadmium and lead on the life-cycle parameters of juvenile earthworm Eisenia fetida

Juveniles Eisenia fetida were exposed to cadmium (1-500µgCdg(-1)) and lead (20-2500µgPbg(-1)) for fourteen weeks in order to evaluate the impact on life-cycle parameters (survival, growth, sexual maturation, and cocoon production) and lipid peroxidation (expressed as concentration of malondialdehyde (MDA)). Both metals were found to significantly affect survival of the juveniles (fourteen-week LC50 296±125µgCdg(-1) and 911±164µgPbg(-1)) and alter their development. Cd and Pb severely affected the weight of the juveniles, prolonged the time to sexual maturation (at the highest concentrations, earthworms did not reach sexual maturity at all), and reduced cocoon production. LC50 significantly decreased with the time of earthworm exposure, indicating that chronic exposure to the same levels of contaminants in the soil may have more detrimental consequences than short-term exposure. A survival model showed that the survival probability for the juveniles decreased significantly with time and the concentration of metals in the soil. The metals induced a significant increase in MDA concentration (2.98-fold and 1.54-fold at 250µgCdg(-1) and 2500µgPbg(-1), respectively), and the content of MDA was negatively related to the weight of the juveniles and the percentage of mature individuals (p<0.05).

Risk assessment of an abandoned pyrite mine in Spain based on direct toxicity assays

This research reports the risk assessment of an abandoned pyrite mine using direct toxicity assays of soil and groundwater samples taken at the site. The toxicity of As and heavy metals from mining soils to soil and aquatic organisms was studied using the Multispecies Soil System (MS-3) in soil columns. Ecotoxicological assessment was performed with soil samples diluted with a control soil at concentrations of 12.5, 25, 50 and 100% test soil/soil (w/w). In this way, changes in the mobility and bioavailability of soil contaminants due to changes in geochemical soil properties via soil dilution were studied. The toxicity of water samples was tested on algae and Daphnia magna. The assessment of the mining area indicated that the current presence of As and heavy metals at the site may cause injuries to soil and aquatic organisms in the entire research area. Moreover, this investigation demonstrated that changes in geochemical conditions can increase the availability of arsenic and, consequently, the environmental risk of these soils. A good correlation was not found between toxicity parameters and the concentrations of soil contaminants based on total and extracted element concentrations. This finding reinforces the usefulness of direct toxicity assays for evaluating environmental risk.

Ecotoxicological effects of a veterinary food additive, copper sulphate, on antioxidant enzymes and mRNA expression in earthworms

The present study was aimed to investigate the effect of the veterinary food additive copper sulphate (CuSO₄) on the eco-toxicological responses of earthworms Eisenia fetida (E. fetida). The following biomarkers were measured: catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione-S-transferase (GST) activities. Gene expression analyses such as metallothionein (MT) and heat shock protein 70 (Hsp70) were also examined. A time-dependent increase of CAT activity was found at 400 mg/kg and SOD activity at 200 and 400 mg/kg. The highest expression of Hsp70 (4.4-fold) was observed at day 15 at 400 mg/kg. Our results indicated that the measured antioxidant enzymes (except GST) had the ability to provide antioxidant defenses against the stressor; and compared to expression of MT, expression of Hsp70 could be more reliable molecular tools with predictive possibilities to monitor the eco-toxicity of stressors such as feed additive CuSO₄.

Toxicological responses of earthworm (Eisenia fetida) exposed to metal-contaminated soils

The aim of this study was to evaluate the toxicological responses of earthworm (Eisenia fetida) induced by field-contaminated, metal-polluted soils. Biochemical responses and DNA damage of earthworm exposed to two multi-metal-contaminated soils in a steel industry park and a natural reference soil in Zijin Mountain for 2, 7, 14, and 28 days were studied. Results showed that three enzyme activities, including superoxide dismutase (SOD), acetylcholinesterase (AChE), and cellulase, in earthworm in metal-contaminated soils were significantly different from those of the reference soil. Cellulase and AChE were more sensitive than SOD to soil contamination. The Olive tail moment of the comet assay after 2-day exposure increased 56.5 and 552.0 % in two contaminated soils, respectively, compared to the reference soil. Our findings show that cellulase and DNA damage levels can be used as potential biomarkers for exposure of earthworm to metal-polluted soils.

Biochemical and genotoxic effect of triclosan on earthworms (Eisenia fetida) using contact and soil tests

Triclosan (TCS) is a broad-spectrum bactericide that is used for a variety of antimicrobial functions. TCS is frequently detected in the terrestrial environment due to application of sewage sludge to agricultural land. In the present study, 48-h paper contact and 28-day spiked soil tests were conducted to examine the toxic effects of TCS on the antioxidative and genetic indices of earthworms (Eisenia fetida). The activity of antioxidative enzymes (superoxide dismutase, SOD; catalase, CAT) and the content of the lipid peroxidation product (malondialdehyde, MDA) were determined as biomarkers of oxidative stress in E. fetida. Moreover, single cell gel electrophoresis (SCGE) was used as a biomarker of genotoxicity. The results showed that triclosan induced a significant increase (P < 0.05) in antioxidative enzyme activities and MDA content. Of all of the biomarkers examined, CAT activity was most sensitive to TCS, and the CAT activity increased significantly (P < 0.05) at bactericidal concentrations of 7.86 ng cm⁻² in the contact test and 10 mg kg⁻¹ in the spiked soil test. The comet assay showed that TCS treatments significantly induced (P < 0.05) DNA damage in E. fetida, and that 78.6 ng cm⁻² caused significant genotoxic effects in the acute test (48 h). Clear dose-dependent DNA damage to E. fetida was observed both in contact and spiked soil tests. These results imply that TCS may have potential biochemical and genetic toxicity toward earthworms (E. fetida). A battery of biomarkers covering multiple molecular targets of acute toxicity can be combined to better understand the impacts of TCS on E. fetida.

Earthworm sublethal responses to titanium dioxide nanomaterial in soil detected by ¹H NMR metabolomics

¹H NMR-based metabolomics was used to examine the response of Eisenia fetida earthworms raised from juveniles for 20-23 weeks in soil spiked with either 20 or 200 mg/kg of a commercially available uncoated titanium dioxide (TiO(2)) nanomaterial (nominal diameter of 5 nm). To distinguish responses specific to particle size, soil treatments spiked with a micrometer-sized TiO(2) material (nominal diameter, <45 μm) at the same concentrations (20 and 200 mg/kg) were also included in addition to an unspiked control soil. Multivariate statistical analysis of the (1)H NMR spectra for aqueous extracts of E. fetida tissue suggested that earthworms exhibited significant changes in their metabolic profile following TiO(2) exposure for both particle sizes. The observed earthworm metabolic changes appeared to be consistent with oxidative stress, a proposed mechanism of toxicity for nanosized TiO(2). In contrast, a prior study had observed no impairment of E. fetida survival, reproduction, or growth following exposure to the same TiO(2) spiked soils. This suggests that (1)H NMR-based metabolomics provides a more sensitive measure of earthworm response to TiO(2) materials in soil and that further targeted assays to detect specific cellular or molecular level damage to earthworms caused by chronic exposure to TiO(2) are warranted.

Case study of water-soluble metal containing organic constituents of biomass burning aerosol

Natural and prescribed biomass fires are a major source of aerosols that may persist in the atmosphere for several weeks. Biomass burning aerosols (BBA) can be associated with long-range transport of water-soluble N-, S-, P-, and metal-containing species. In this study, BBA samples were collected using a particle-into-liquid sampler (PILS) from laboratory burns of vegetation collected on military bases in the southeastern and southwestern United States. The samples were then analyzed using high resolution electrospray ionization mass spectrometry (ESI/HR-MS) that enabled accurate mass measurements for hundreds of species with m/z values between 70 and 1000 and assignment of elemental formulas. Mg, Al, Ca, Cr, Mn, Fe, Ni, Cu, Zn, and Ba-containing organometallic species were identified. The results suggest that the biomass may have accumulated metal-containing species that were re-emitted during biomass burning. Further research into the sources, dispersion, and persistence of metal-containing aerosols, as well as their environmental effects, is needed.

Screening risk assessment tools for assessing the environmental impact in an abandoned pyritic mine in Spain

This paper describes a new methodology for assessing site-specific environmental impact of contaminants. The proposed method integrates traditional risk assessment approaches with real and variable environmental characteristics at a local scale. Environmental impact on selected receptors was classified for each environmental compartment into 5 categories derived from the whole (chronic and acute) risk assessment using 8 risk levels. Risk levels were established according to three hazard quotients (HQs) which represented the ratio of exposure to acute and chronic toxicity values. This tool allowed integrating in only one impact category all the elements involved in the standard risk assessment. The methodology was applied to an abandoned metal mine in Spain, where high levels of As, Cd, Zn and Cu were detected. Risk affecting potential receptors such as aquatic and soil organisms and terrestrial vertebrates were assessed. Whole results showed that impact to the ecosystem is likely high and further investigation or remedial actions are necessary. Some proposals to refine the risk assessment for a more realistic diagnostic are included.

Risk assessment of pesticides and heavy metals contaminants in vegetables: a novel bioassay method using Daphnia magna Straus

Cucumber and potato samples of known levels of pesticides and heavy metal residues, as respectively measured by gas chromatography and atomic absorption, were subjected to a bioassay method using Daphnia magna in order to assess the potential of the toxic hazard of their contaminants. Based on the estimated lethal time for 50% mortality (LT50) in daphnids, we suggested a classification to categorize toxic hazards in six definite ratings. Either samples of cucumbers (from conventional, greenhouse and organic farming) or potatoes (from conventional and organic farming) were evaluated for toxic hazard of the mixtures of pesticide residues and heavy metals, as well as mixtures of both. Accordingly, a 53.7% of cucumber samples were ranked as "Highly Toxic: HT"; a 18.5% "Moderately Toxic: MT); a 9.3% "Slightly Toxic: ST"; and a 18.5% "Practically Non-Toxic: NT". For potato samples, the ranking pattern to different classes was: Extremely Toxic: ET (LT50=<1h) for 11.1%; Very Toxic: VT (LT50=1-<3h) for 50.0%; HT (LT50=3-<12h) for 13.9%; MT (LT50=12-<24h) for 11.1%; ST (LT50=24-48 h) for 0.0%; and NT (LT50= >48 h) for 13.9% of the samples bioassayed.