Evaluation of single and joint toxicity of perfluorooctanoic acid and arsenite to earthworm (Eisenia fetida): A multi-biomarker approach

Nickel oxide nanoparticles decrease the accumulation of atrazine in earthworms

Nickel oxide nanoparticles (NiO-NPs) are common nanomaterials that may be released into the environment, affecting the toxicity of other contaminants. Atrazine (ATZ) is a commonly used herbicide that can harm organisms due to its persistence and bioaccumulation in the environment. Although the toxicity of ATZ to earthworms is well-documented, the risk of co-exposure with NiO-NPs increases as more nanoparticles accumulate in the soil. In this study, we investigated the effects and mechanisms of NiO-NPs on the accumulation of ATZ in earthworms. The results showed that after day 21, the antioxidant system of the cells under ATZ treatment alone was adversely affected, with ROS content 36.05 % higher than that of the control (CK) group. However, the addition of NiO-NPs reduced the ROS contents in the earthworms by 0.6 %- 32.3 %. Moreover, analysis of earthworm intestinal sections indicates that NiO-NPs mitigated cellular and tissue damage caused by ATZ. High-throughput sequencing revealed that NiO-NPs in earthworm intestines increased the abundance of Pseudomonas aeruginosa and Aeromonas aeruginosa. Additionally, the enhanced function of the ABC transport system in the gut resulted in lower accumulation of ATZ in earthworms. In summary, NiO-NPs can reduce the accumulation and thus the toxicity of ATZ in earthworms. Our study contributes to a deeper understanding of the effects of NiO-NPs on co-existing pollutants.

The bioaccumulation and ecotoxicity of co-exposure of per(poly)fluoroalkyl substances and polystyrene microplastics to Eichhornia crassipes

Gen X and F-53B have been popularized as alternatives to PFOA and PFOS, respectively. These per(poly)fluoroalkyl substances pervasively coexist with microplastics (MPs) in aquatic environments. However, there are knowledge gaps regarding their potential eco-environmental risks. In this study, a typical free-floating macrophyte, Eichhornia crassipes (E. crassipes), was selected for hydroponic simulation of a single exposure to PFOA, PFOS, Gen X, and F-53B, and co-exposure with polystyrene (PS) microspheres. F-53B exhibited the highest bioaccumulation followed by Gen X, PFOA, and PFOS. In the presence of PS MPs, the bioavailabilities of the four PFASs shifted and the whole plant bioconcentration factors improved. All four PFASs induced severe lipid peroxidation, which was exacerbated by PS MPs. The highest integrated biomarker response (IBR) was observed for E. crassipes (IBR of shoot: 30.01, IBR of root: 22.79, and IBR of whole plant: 34.96) co-exposed to PS MPs and F-53B. The effect addition index (EAI) model revealed that PS MPs showed antagonistic toxicity with PFOA and PFOS (EAI < 0) and synergistic toxicity with Gen X and F-53B (EAI > 0). These results are helpful to compare the eco-environmental impacts of legacy and alternative PFASs for renewal process of PFAS consumption and provide toxicological, botanical, and ecoengineering insights under co-contamination with MPs.

Biomarker response index in earthworms following chronic exposure to leachate from a closed dumpsite: Behavioral, cytotoxicity and antioxidant system alterations

Leachate, an effluent produced during solid waste decomposition, interacts directly with soil, mainly in dumpsite areas. Studies on terrestrial animal exposure to leachate are, however, lacking. Plants are the most frequently studied organisms, while animal studies, especially earthworms, are limited. Nevertheless, ecotoxicological assessments involving earthworms are crucial due to their role in soil health and ecosystem maintenance, which are paramount in understanding potential terrestrial ecosystem leachate effects. In this context, this study aimed to evaluate behavioral effects, sublethal cytotoxicity and antioxidant system alterations in Eisenia andrei earthworms chronically exposed to leachate from a closed dumpsite. Cytotoxicity was determined by coelomocyte density, viability and cell typing, while antioxidant system alterations were assessed through superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), reduced glutathione (GSH) and metallothionein (MT) determinations. Malondialdehyde (MDA) and protein carbonylation (PTC) levels were also determined as oxidative effect markers. Finally, the Biomarker Response Index (BRI) was assessed, aiming to quantitatively integrate the results of the investigated endpoints and establish a biological health state (BHS) for each leachate concentration. Leachate exposure led to leak responses at concentrations of up to 50%, but attraction at higher concentrations. Decreased cell density (28%) was observed after 48 days and reduced viability (50%), after 14 days of leachate exposure. The observed cell typing changes indicate anti-inflammatory immune system effects. Leachate exposure led to several antioxidant system alterations, increasing SOD (2-6 %), CAT (5-35 %) and GST (5-70 %) activities and GSH (7-37%) and MT (3-67%) levels. Earthworm antioxidant defenses were, however, able to prevent lipid peroxidation, which decreased (11-37%) following leachate exposure to concentrations above 12.5%, and PTC, which increased at 42 days (26%) and reduced at 56 days (12 %). This is the first PTC assessment in leachate-exposed earthworms. The increased carbonylation levels observed after 42 days alongside MDA decreases highlight the need for further research employing oxidative effect biomarkers other than MDA. Finally, an integrated approach employing the BRI was carried out, revealing mild initial changes evolving to moderate to major effects at the highest leachate exposure concentration, with an effect attenuation detected at the end of the experiment. In this sense, this study brings forth a significant novelty, employing a biomarker previously not assessed in earthworms, demonstrating an oxidative effect, alongside the use of the BRI as an integrative tool for the endpoints applied in this assessment.

Ecotoxicological effects of soil lithium on earthworm Eisenia fetida: Lethality, bioaccumulation, biomarker responses, and histopathological changes

Lithium is an emerging environmental contaminant in the current low-carbon economy, but little is known about its influences on soil invertebrates. In this work, earthworm Eisenia fetida was exposed to soils treated with different levels of lithium for 7 d, and multiple ecotoxicological parameters were evaluated. The results showed that mortality was dose-dependent and lithium's median lethal content (LC₅₀) to earthworm was respectively 865.08, 361.01, 139.36, and 94.95 mg/kg after 1 d, 2 d, 4 d, and 7 d exposure. The bioaccumulation factor based on measured exogenous lithium content (BF_exog) respectively reached 0.79, 1.01, 1.57, and 1.27 with the increasing lithium levels, suggesting that lithium accumulation was averagely 1.16-fold to the exogenous content, and 74.42%∼81.19%, 14.54%∼18.23%, and 2.26%∼8.02% of the lithium in exposed earthworms were respectively retained in the cytosol, debris, and granule. Then, lithium stress stimulated the activity of superoxide dismutase, peroxidase, catalase, acetylcholinesterase, and glutathione S-transferase as well as the content of 8-hydroxy-2-deoxyguanosine and metallothionein, indicating the generation of oxidative damage, while the content of reactive oxygen species and malondialdehyde decreased. Finally, lithium introduced histopathological changes, including the degenerated seminal vesicle and muscle hyperplasia, as well as high or extreme nuclear DNA damage. This study confirmed the obvious bioaccumulation and toxic effects caused by soil lithium via ecotoxicological data, providing new theoretical insights into understanding the ecological risks of lithium to soil invertebrates.

Accumulation and speciation of arsenic in Eisenia fetida in sodium arsenite spiked soils - A dynamic interaction between soil and earthworms

Arsenic (As) is a toxic metalloid that is a significant global pollutant of the environment and a persistent bioaccumulation carcinogen. Earthworms are frequently employed as sentinel organisms to investigate the bioavailability of As in contaminated soils. However, the process of As accumulation in earthworms and the mechanism of transformation of As species in their bodies are not well understood. The accumulation of As and variation of As species in the earthworms (Eisenia fetida) exposed to sodium arsenite (0, 20, and 80 mg kg^-1 As) were investigated in this study. The total As concentration of earthworms in the three treatments at various sample times was dose-dependent on soil As content. After 56 days of exposure, the high concentration treatment had the highest total As content (772 ± 21 mg kg^-1) in earthworms, followed by the low concentration treatment (579 ± 42 mg kg^-1) and control (31 ± 1 mg kg^-1). During 56 days, the proportion of trivalent As in earthworms increased from 70% to more than 90%, while pentavalent As decreased by 11-18%. On day 28, the sum of the four organic As species reached a maximum (<1%). Changes in soil As species and an increase in bioavailable As cause earthworms to accumulate more As. The total As in soil after 56 days of exposure was 9.51 ± 0.50, 25.6 ± 0.60, and 82.8 ± 0.28 mg kg^-1, which was not significantly different from the total As in soil before the experiment. These findings are useful in assessing the risk of earthworm exposure to sodium arsenite in the soil.

Vermitoxicity of aged biochar and exploring potential damage factors

Although biochar is a promising soil amendment, its characteristics change owing to its aging in soil. Studies have shown that some aged biochar is hazardous to plants and soil microbiota. Earthworms are well-known soil ecosystem engineers; nevertheless, the toxic effects of aged biochar on them (vermitoxicity) are yet unknown, and it is necessary to explore the potential risk factors. Here, a series of soil culture experiments were conducted to systematically examine the vermitoxicity of aged biochar at various levels utilizing the earthworm Eisenia fetida and corncob biochar.. Acute toxicity bioassays were also used to evaluate several potential harm factors utilizing modified aged biochar/leaching solutions. The findings showed that both fresh and aged biochar might have adverse effects on earthworms, and that aged biochar was more toxic than fresh biochar with LC₅₀s reduced to 6.89%. Specifically, aged biochar caused earthworm death, growth inhibition with a maximum of 36.6%, and avoidance with 100% avoidance at the application rates of 2% at the individual-behavioral level. At the cellular and physiological-biochemical levels, aged biochar damaged coelomocyte lysosomal membrane stability, disrupted antioxidant enzyme activities, and improved the malondialdehyde (MDA) content in earthworms. Heat-treated and pH-modified aged biochar exhibited less acute toxicity on earthworms than aged biochar, whereas aqueous and acetone extracts showed weak vermitoxicity. As a result, earthworms may be harmed by volatile organic compounds (VOCs), an improper pH, and aqueous and acetone extracts. Additionally, the range of neural red retention times (NRRTs) was reviewed as ∼20-70 min mostly. This study, as far as we know, is the first to evaluate the vermitoxicity of aged biochar and its potential damage factors. The results may enhance our understanding of ecological toxicity of biochar, particularly over the long term, and lead to the development of application standards for biochar amendments to the soil.

How do different arsenic species affect the joint toxicity of perfluorooctanoic acid and arsenic to earthworm Eisenia fetida: A multi-biomarker approach

Perfluorooctanoic acid (PFOA) and arsenic are widely distributed pollutants and can coexist in the environment. However, no study has been reported about the effects of different arsenic species on the joint toxicity of arsenic and PFOA to soil invertebrates. In this study, four arsenic species were selected, including arsenite (As(III)), arsenate (As(V)), monomethylarsonate (MMA), and dimethylarsinate (DMA). Earthworms Eisenia fetida were exposed to soils spiked with sublethal concentrations of PFOA, different arsenic species, and their binary mixtures for 56 days. The bioaccumulation and biotransformation of pollutants, as well as eight biomarkers in organisms, were assayed. The results indicated that the coexistence of PFOA and different arsenic species in soils could enhance the bioavailability of arsenic species while reducing the bioavailability of PFOA, and inhibit the arsenic biotransformation process in earthworms. Responses of most biomarkers in joint treatments of PFOA and As(III)/As(V) showed more significant variations compared with those in single treatments, indicating higher toxicity to the earthworms. The Integrated Biomarker Response (IBR) index was used to integrate the multi-biomarker responses, and the results also exhibited enhanced toxic effects in combined treatments of inorganic arsenic and PFOA. In comparison, both the biomarker variations and IBR values were lower in joint treatments of PFOA and MMA/DMA. Then the toxic interactions in the binary mixture systems were characterized by using a combined method of IBR and Effect Addition Index. The results revealed that the toxic interactions of the PFOA/arsenic mixture in earthworms depended on the different species of arsenic. The combined exposure of PFOA with inorganic arsenic led to a synergistic interaction, while that with organic arsenic resulted in an antagonistic response. Overall, this study provides new insights into the assessment of the joint toxicity of perfluoroalkyl substances and arsenic in soil ecosystems.