Effects of antimony contamination on bioaccumulation and gut bacterial community of earthworm Eisenia fetida

Effective immobilization and biosafety assessment of antimony in soil with zeolite-supported nanoscale zero-valent iron

Antimony (Sb) contamination in certain areas caused by activities such as antimony mining and smelting poses significant risks to human health and ecosystems. In this study, a stable composite material consisting of natural zeolite-supported nanoscale zero-valent iron (Z-ZVI) was successfully prepared. The immobilization effect of Z-ZVI on Sb in contaminated soil was investigated. Experimental results showed that Z-ZVI exhibited superior performance compared to pure nano zero-valent iron (nZVI) in terms of stability, with a lower zeta potential (-25.16 mV) at a pH of 7 and a higher specific surface area (54.54 m2/g). It can be easily applied and dispersed in contaminated soils. Additionally, Z-ZVI demonstrated a more abundant porous structure. After 60 days of treatment with 3% Z-ZVI, the leaching concentration of Sb in the contaminated soil decreased from 1.32 mg/L to 0.31 mg/L (a reduction of 76%), and the concentration of available Sb species decreased from 19.84 mg/kg to 0.71 mg/kg, achieving a fixation efficiency of up to 90%. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis confirmed the effective immobilization of Sb in the soil through reduction of antimonate to antimonite, precipitation, and adsorption processes facilitated by Z-ZVI. Moreover, the addition of Z-ZVI effectively reduced the bioavailability of Sb in the contaminated soil, thereby mitigating its toxicity to earthworms. In conclusion, Z-ZVI can be utilized as a promising material for the safe remediation and antimony and other heavy metal-contaminated soils.

Exploring the toxicity of biodegradable microplastics and imidacloprid to earthworms (Eisenia fetida) from morphological and gut microbial perspectives

Biodegradable microplastics (BMPs) pose serious environmental problems to soil organisms, and their adsorption capacity might make pesticides more dangerous for soil organisms. Therefore, in this study, polylactic acid (PLA) BMPs and imidacloprid (IMI) were used as a representative of BMPs and pesticides, respectively. Eisenia fetida was used as a test animal to investigate the effects of environmentally relevant concentrations of single and compound contaminated PLA BMPs and IMI on mortality, growth, number of offspring, tissue damage, and gut microorganisms of E.fetida. Exposure to PLA BMPs treatment and PLA BMPs + IMI treatment resulted in a sustained increase in E.fetida mortality, reaching 16.7% and 26.7%, respectively. The growth inhibition rate of single treatments was significantly increased. The compound contamination had the greatest effect on E.fetida offspring compared to the control. PLA BMPs and IMI cause histological damage to E.fetida, with the compound treatment causing the most severe damage. Based on the results of 16S sequencing, the bacterial communities in E.fetida gut and soil treated to PLA BMPs and IMI were significantly different. PLA BMPs + IMI treatment suppresses the abundance and diversity of E.fetida gut microorganisms, disrupting the homeostasis of bacterial communities and causing immune and metabolic dysfunction. These findings highlight the more severe damage of combined PLA BMPs and IMI pollution to E.fetida, and help to assess the risk of earthworm exposure to environmentally relevant concentrations of PLA BMPs and IMI.

Integrated microbiome and multi-omics analysis reveal the molecular mechanisms of Eisenia fetida in response to biochar-derived dissolved and particulate matters

At present, most ecotoxicological studies are still confined to focusing on the harmful effects of biochar itself on soil fauna. However, the potential ecotoxicity of different components separated from biochar to terrestrial invertebrates remains poorly understood. In this study, the dissolved matter (DM) and particulate matter (PM) were separated from biochar (BC) and then introduced into the soil-earthworm system to investigate the response mechanism of earthworms at the molecular level. The results showed that BC and DM exposure caused an increase in the abundance of Proteobacteria in the cast bacterial community, suggesting the dysbiosis of intestinal microbiota. It was also observed that the cast bacterial communities were more sensitive to DM exposure than PM exposure. Transcriptomic analysis showed that BC and DM exposure induced significant enrichment of functional pathways related to infectious and neuropathic diseases. Metabolomic profiling manifested that DM exposure caused metabolic dysfunction, antioxidant and detoxification abilities recession. Furthermore, significant differences in the responses of earthworms at transcriptomic and metabolic levels confirmed that DM exhibited greater ecotoxicity than PM. This study highlighted the significant contributions of dissolved matter to the ecotoxicity of biochar from the perspective of transcriptomic and metabolomic profiles.

Microplastics in feed cause sublethal changes in the intestinal microbiota and a non-specific immune response indicator of the freshwater crayfish Procambarus clarkii (Decapoda: Cambaridae)

Microplastics (MP) are a hazardous pollutant of global concern that threatens aquatic ecosystems and public health. We used the invasive, cosmopolitan, and environmentally versatile red swamp crayfish Procambarus clarkii as a model to study the effects of MP on the intestinal microbiome. Crayfish collected from the environment were compared with specimens exposed to recycled Polyethylene terephthalate (rPET) MP in feed (30%) for 96 h in the laboratory and a control group. We analyzed the 16S rRNA of the intestinal bacteria by PCR-DGGE and high-throughput sequencing. MP exposure caused dysbiosis of the intestinal microbiota, with an increase in Alphaproteobacteria and Actinobacteria. We detected higher abundance of opportunistic genera such as Klebsiella, Acinetobacter, Hydromonas, Pseudomonas, Gemmobacter, and Enterobacter on MP fed organisms. Moreover, MP exposure reduced the abundance of Clostridia and Bateroidetes, which are important for immune system development and pathogen prevention. Furthermore, MP exposure decreased the phenoloxidase (PO) immune response in crayfish. There was a significant difference in the richness of intestinal bacterial communities after consumption of food contaminated with MP, likely increasing the abundance of opportunistic bacteria in the intestinal microbiota. Our results suggest that MP alter the gut microbial composition and impair the health of P. clarkii.

Pollution characteristics and risk assessment of antimony and arsenic in a typical abandoned antimony smelter

Antimony (Sb) and arsenic (As) co-contamination occurs in Sb smelting areas and is harmful to the surrounding ecological environment. The purpose of this study is to explore the spatial distribution characteristics of Sb and As in abandoned Sb smelting area and carry out risk assessments. Soil samples were collected from the smelting area profile and background points, and groundwater samples were also collected. Samples from two geological background sections were collected to understand the geological background characteristics of Sb and As. The spatial distribution was drawn via the inverse distance weighted interpolation method. The hazard assessment was carried out by the geo-accumulation index and potential ecological hazard methods. The results showed that special high geological background value of Sb and As in study area. Sb and As co-contamination is one of the characters in soil. And the contents of Sb and As decrease as depth increases, reflecting the weak migration capacity. The spatial distribution of Sb and As is affected by slag distribution and rainfall leaching. The Sb content in groundwater was higher in the wet and normal seasons than in the dry season, slag leaching may be one of the elements. The potential ecological hazards of Sb and As are high and considerable, respectively. In abandoned smelting area with high geological background values, it is necessary to focus on the pollution abatement and protection of ecological health.

New insights into the effects of antibiotics and copper on microbial community diversity and carbon source utilization

Residual antibiotics (ABs) and heavy metals (HMs) are continuously released from soil, reflecting their intensive use and contamination of water and soil, posing an environmental problem of great concern. Relatively few studies exist of the functional diversity of soil microorganisms under the combined action of ABs and HMs. To address this deficiency, BIOLOG ECO microplates and the Integrated Biological Responses version 2 (IBRv2) method were used to comprehensively explore the effects of single and combined actions of copper (Cu) and enrofloxacin (ENR), oxytetracycline (OTC), and sulfadimidine (SM2) on the soil microbial community. The results showed that the high concentration (0.80 mmol/kg) compound group had a significant effect on average well color development (AWCD) and OTC showed a dose-response relationship. The results of IBRv2 analysis showed that the single treatment group of ENR or SM2 had a significant effect on soil microbial communities, and the IBRv2 of E1 was 5.432. Microbes under ENR, SM2, and Cu stress had more types of available carbon sources, and all treatment groups were significantly more enriched with microorganisms having D-mannitol and L-asparagine as carbon sources. This study confirms that the combined effects of ABs and HMs can inhibit or promote the function of soil microbial communities. In addition, this paper will provide new insights into IBRv2 as an effective method to evaluate the impacts of contaminants on soil health.

Ecological adaptation of earthworms for coping with plant polyphenols, heavy metals, and microplastics in the soil: A review

In recent years, soil pollution by massive accumulation of heavy metals (HMs), microplastics, and refractory hydrocarbon chemicals has become an emerging and global concern, drawing worldwide attention. These pollutants influence soil diversity by hindering the reproduction, abundance, thereby affecting aboveground productivity. The scientific community has recently emphasized the contribution of earthworms to heavy metal accumulation, microplastic degradation, and the decomposition of organic matter in the soil, which helps maintain the soil structure. This review paper aimed to compile scientific facts on how earthworms cope with the effect of HMs, microplastics, and plant polyphenols so that vermiremediation could be widely applied for well-being of the soil ecosystem by environmentalists. Earthworms have special surface-active metabolites in their guts called drilodefensins that help them defend themselves against the oxidative action of plant polyphenols. They also combat the effects of toxic microplastics, and other oxidative compounds by elevating the antioxidant activities of their enzymes and converting them into harmless compounds or useful nutrients. Moreover, earthworms also act as biofilters, bioindicators, bioaccumulators, and transformers of oxidative polyphenols, microplastics, toxic HMs, and other pollutant hydrocarbons. Microorganisms (fungi and bacteria) in earthworms' gut of also assist in the fixation, accumulation, and transformation of these toxicants to prevent their effects. As a potential organism for application in ecotoxicology, it is recommended to propagate earthworms in agricultural fields; isolate, and culture enormously in industry, and inoculate earthworms in the polluted soil, thereby abate toxicity and minimizing the health effect caused by these pollutants as well enhance the productivity of crops.

Stereoselective accumulation and biotransformation of chiral fungicide epoxiconazole and oxidative stress, detoxification, and endogenous metabolic disturbance in earthworm (Eisenia foetida)

>80 % of applied pesticides in agriculture will enter the soil and be exposed to soil animals. Little is known about the stereoselective metabolic effects of epoxiconazole (EPO) on soil animals. In this study, EPO-mediated stereoselective enrichment, biotransformation, oxidative stress, detoxification, and global metabolic profiles in earthworms were investigated by exposure to EPO and its enantiomers at 1 mg/kg and 10 mg/kg doses. Preferential enrichment of (-)-EPO was observed, and the five transformation products (TPs) exhibited the chemically specific stereoselective accumulation with inconsistent configurations. Biochemical markers related to reactive oxygen species (ROS) and detoxification (·OH^- content, SOD, CAT, GST, and CYP450 enzymes) showed a significant stereoselective activation overall at the low-level exposure (p-value <0.05). Based on untargeted metabolomic analysis, the steroid biosynthesis and ROS-related biotransformation, glutathione metabolism, TCA cycle, amino acid metabolism, purine and pyrimidine metabolism of earthworms were significantly interfered with by EPO and its enantiomer exposure. More pronounced stereoselectivity was observed at the level of the global metabolic profile, while comparable levels of metabolic perturbations were identified at the individual metabolite level. This study provides novel insights into the stereoselective effects of the chiral fungicide EPO, and valuable evidence for soil environmental risk assessments.

The overlooked toxicity of environmentally persistent free radicals (EPFRs) induced by anthracene transformation to earthworms (Eisenia fetida)

Environmentally persistent free radicals (EPFRs) as intermediate products exist widely in the PAHs-contaminated soils, but toxicity assessment associated with EPFRs for terrestrial invertebrates remains unclear. Using the model organism Eisenia fetida, we compared the adverse effects among anthracene (ANT), anthraquinone (ANQ), and EPFRs induced by ANT transformation on clay surfaces. Our results showed that EPFRs-exposed earthworms experienced histopathological damage, which was more severe than ANT and ANQ-exposed earthworms. The source of EPFRs damage was associated with the obvious dysbiosis of reactive oxygen species in earthworms. Specifically, EPFRs trigged more severe antioxidant responses and oxidative damages (e.g., membrane lipid and DNA injury) in comparison with ANT and ANQ exposure, as evidenced by the values of integrated biomarker response (IBR) following the order of EPFRs (14.5) > ANT (12.8) > ANQ (10.9). Moreover, high-throughput sequencing found that EPFRs induced dramatic changes in the composition and structure of earthworm gut microbiota, which may involve immune and metabolism dysfunction, in turn aggravated EPFRs toxicity. Overall, the obtained information highlights the more severe injury of EPFRs to terrestrial organisms, deserving more attentions for the assessment of potential risks associated with radical intermediates in PAHs-contaminated soils.

Response of soil protists to antimony and arsenic contamination

Microorganisms can mediate antimony (Sb) and arsenic (As) transformation and thus change their mobility and toxicity. Having similar geochemical behavior, Sb and As are generally considered to exert similar environmental pressure on microbiome. However, it needs further validation, especially for protists. In this study, the responses of protistan communities to Sb and As were investigated by collecting soils from Xikuangshan Sb mine and Shimen As mine in China. Antimony and As contamination taxonomically and functionally (consumer and phototroph) changed the alpha and beta diversities of protistan communities, but exerted different impacts on the parasitic community. Based on multiple statistical tools, As contamination had a greater impact on protistan communities than Sb. The ecological networks of highly contaminated sites were less complex but highly positively connected compared to less contaminated sites. High As contamination raised the ratio of consumers and decreased the ratio of phototrophs in ecological networks, while the opposite tendency was observed in Sb contaminated soils. High Sb and As contamination enriched different keystone taxa resistant to Sb and As. These results demonstrate that protistan community respond differently to Sb and As.

Source, Distribution and Potential Risk of Antimony in Water and Sediments of Danjiangkou Reservoir: Impact from Dam

Danjiangkou Reservoir is the water source of the mid-route of the South-to-North Water Transfer Project. The source, distribution and potential risk of antimony in its water and sediments are rarely reported. In this study, symmetrical investigation results demonstrated that the concentration of antimony in the Han sub-reservoir and water in front of the dam fluctuated at about 0.9 mg L^-1, while it was relatively higher and increased with the distance from the dam in Dan sub-reservoir water, with an annual average of 0.93~3.15 mg L^-1. In recent years, the concentration of antimony in the Danjiangkou Reservoir showed a downward trend, and the difference between the Han and Dan sub-reservoirs decreased significantly. The antimony in the sediments in the reservoir was primarily derived from the inflowing rivers, and it was higher in the Dan sub-reservoir than in the Han sub-reservoir. The concentration of antimony in the water in the reservoir was considerably higher than the background value in the watersheds, indicating that there is an external input with decreasing input intensity. The content of antimony in the sediments in the reservoir and its inflow rivers was substantially higher than the background value of watersheds, indicating that there is a certain degree of enrichment. In addition, the antimony mining industry in the water source area poses a risk to the water safety of the reservoir. Antimony is not a conventional pollutant. Consequently, the collection of antimony monitoring results is a challenging task. Additionally, this study fills the gap in regional antimony research. Furthermore, the ecological risk assessment of antimony in China is still in its infancy. Unquestionably, the study of the temporal and spatial distribution of antimony concentration will be beneficial for the protection of water sources in relevant regions.

Environmental behavior of the chiral fungicide epoxiconazole in earthworm-soil system: Enantioselective enrichment, degradation kinetics, chiral metabolite identification, and biotransformation mechanism

The environmental impact of the chiral fungicide epoxiconazole and its chiral transformation products (TPs) on non-target organisms and the environment has become a significant concern due to its widespread use in agricultural practice. Enantioselectivity studies of parent contaminants cannot adequately assess the complexity of its chiral TPs in the environment. This study aimed to investigate the environmental behavior of epoxiconazole in an earthworm-soil system. 2S,3R-(-)-epoxiconazole was preferentially enriched in earthworms during the accumulation phase (p < 0.05), but no enantioselectivity was observed during the elimination phase. One methoxylated and four hydroxylated chiral TPs were identified in soil, earthworm, and excrement. The epoxy ring hydroxylated TP and methoxylated TP of epoxiconazole were discovered for the first time in the environment. The chemically specific enantioselectivity with enantiomer fraction (EF) > 0.8 was observed for the TPs in different matrices. The CYP450 monooxygenase of earthworm was significant activated. In vitro enzyme metabolism experiments (earthworm microsomes and recombinant CYP450 enzymes CYP2A6, CYP 2C9, and CYP 3A4) were carried out to further explain the biotransformation mechanism of epoxiconazole in earthworm. This study provides new evidence of enantiomeric biotransformation of chiral fungicide epoxiconazole in the earthworm-soil system and could provide valuable insights into their environmental risk assessment.

Earthworm half-pipe assay: A new alternative in vivo skin corrosion test using invertebrates

As a result of the efforts to introduce the principle of the 3Rs (replacement, reduction, and refinement) into animal testing, alternative in vitro skin corrosion test methods have been developed and standardized globally. However, alternative in vitro skin corrosion test methods have some limitations in terms of the use of humanely killed rats or commercial models and kits. The present study focused on the applicability of invertebrates as alternative in vivo skin models. Even though earthworm skin comprises the same biomolecules as human skin, the possibility of using earthworm skin as an alternative for skin testing remains unexplored. In this study, we developed a half-pipe tool for earthworm skin corrosion testing and optimized the test protocol. Subsequently, the applicability of the earthworm half-pipe assay for corrosion testing with six chemicals, including inorganic acids, organic acids, and alkalis, was investigated using stereomicroscopy and electron microscopy. It was observed that the specific concentrations for earthworm skin corrosion were lower than those for animal or in vitro tests. Therefore, the sensitivity of the earthworm half-pipe assay indicates that it could be useful as a screening tool before conducting in vivo animal tests or in vitro skin tests. This new method can contribute to research on alternative skin corrosion tests by reducing ethical issues, time, and cost while achieving effective results.

Effects of diisononyl phthalate exposure on the oxidative stress and gut microorganisms in earthworms (Eisenia fetida)

Phthalate esters (PAEs) are widely used as plasticizers and can be ubiquitously detected in environment. However, the toxic effects and mechanisms of diisononyl phthalate (DINP) on earthworms are still poorly understood. In this study, earthworms (Eisenia fetida) were exposed to DINP at various doses (0, 300, 600, 1200, and 2400 mg/kg) to investigate their subchronic toxicity. The results demonstrated that the reactive oxygen species (ROS) levels displayed an "increase-decrease" trend with the increasing DINP doses after DINP exposure on days 7, 14, 21, and 28. The malondialdehyde (MDA) content increased with increasing DINP doses on days 7, 14, and then decreased on days 21, 28. The values of superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST) showed similar variation patterns and reached a maximum level on 21 d. Moreover, on day 28, the SOD and CAT gene expression levels were upregulated, while the GST gene expression levels were downregulated. Meanwhile, 16S rRNA genes of E. fetida gut bacteria and surrounding soil bacteria were measured after 28 days of exposure to DINP. The Chao index of E. fetida gut bacteria decreased when the treatment with the highest concentration (2400 mg/kg) was applied. At the phylum level, the abundance of Chloroflexi was significantly lower in the gut of E. fetida. In addition, the abundance of Proteobacteria at the phylum level and Ottowia at the genus level significantly increased in the surrounding soil. Overall, our results shed light on the toxic mechanism of DINP at biochemical, molecular, and omics levels, and contributed to a better understanding of the ecotoxicity of DINP.

Importance-Based Key Basic Event Identification and Evolution Mechanism Investigation of Hydraulic Support Failure to Protect Employee Health

Background: Although hydraulic support can help enterprises in their production activities, it can also cause fatal accidents. Methods: This study established a composite risk-assessment method for hydraulic support failure in the mining industry. The key basic event of hydraulic support failure was identified based on fault tree analysis and gray relational analysis, and the evolution mechanism of hydraulic support failure was investigated based on chaos theory, a synthetic theory model, and cause-and-effect-layer-of-protection analysis (LOPA). Results: After the basic events of hydraulic support failure are identified based on fault tree analysis, structure importance (SI), probability importance (PI), critical importance (CI), and Fussell–Vesely importance (FVI) can be calculated. In this study, we proposed the Fussell–Vesely–Xu importance (FVXI) to reflect the comprehensive impact of basic event occurrence and nonoccurrence on the occurrence probability of the top event. Gray relational analysis was introduced to determine the integrated importance (II) of basic events and identify the key basic events. According to chaos theory, hydraulic support failure is the result of cross-coupling and infinite amplification of faults in the employee, object, environment, and management subsystems, and the evolutionary process has an obvious butterfly effect and inherent randomness. With the help of the synthetic theory model, we investigated the social and organizational factors that may lead to hydraulic support failure. The key basic event, jack leakage, was analyzed in depth based on cause-and-effect-LOPA, and corresponding independent protection layers (IPLs) were identified to prevent jack leakage. Implications: The implications of these findings with respect to hydraulic support failure can be regarded as the foundation for accident prevention in practice.