Thallium (Tl) is a highly toxic heavy metal. It is widely spread in soil. However, the effects of Tl on soil invertebrates have received limited attention. Eisenia fetida, a sensitive and widely used bioindicator, is important in assessing ecological risks in soil ecosystems. It is conceivable that the stress resistance of E. fetida may vary depending on its diet, potentially influencing the assessment of ecological risks associated with contaminants. This study aims to assess the toxicological effects of Tl in soil on E. fetida, focusing on mechanisms involving Tlinduced oxidative stress, disruption of antioxidant defenses, and diet-mediated differences in physiological tolerance. E. fetida was nourished with yogurt waste or cow dung as their primary food source before exposure. The research showed a significant correlation between the increase in soil Tl levels and its bioaccumulation in E. fetida. The highest Tl accumulation was observed in E. fetida fed with yogurt waste (5.55 mu g g-1), exceeding those fed with cow dung (4.77 mu g g-1). Tl inhibited the growth of E. fetida and induced oxidative stress responses. The activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) initially increased at lower concentrations and earlier time points but were suppressed at higher Tl concentrations and longer exposures. In contrast, glutathione S-transferase (GST) and glutathione peroxidase (GPx) activities were generally elevated, especially in yogurt waste-fed worms. Additionally, reduced glutathione (GSH) levels declined over time, while malondialdehyde (MDA) levels increased significantly, indicating lipid peroxidation and oxidative damage. Furthermore, the Integrated Biomarker Response index indicated that cow dung-fed E. fetida exhibited a higher level of toxic stress when compared to those fed with yogurt waste. In a comparative analysis, despite accumulating more Tl, yogurt waste-fed E. fetida exhibited a lower overall toxic response than their cow dung-fed counterparts. Our results suggest that the diet, specifically yogurt waste, can enhance Tl tolerance in E. fetida. Hence, when assessing the ecological risk of Tl concerning earthworms, it is imperative to consider their dietary sources to increase the scientific validity of evaluation results.

Microplastics (MPs), which are widely dispersed in terrestrial environments, threaten crop growth and human food security. However, plant accumulation and phytotoxicity related to the size effects of MPs remain insufficiently explored. This study investigated the accumulation and toxicity of two sizes of MPs on Capsicum annuum Linn. (C. annuum) through fluorescence tracing and antioxidant defense system assessment. The results revealed that the size of MPs significantly impacts their accumulation characteristics in C. annuum roots, leading to variations in toxic mechanisms, including oxidative stress and damage. Smaller MPs and higher exposure concentrations result in more pronounced growth inhibition. C. annuum roots have a critical size threshold for the absorption of MPs of approximately 1.2 mu m. MPs that enter the root tissue exhibit an aggregated form, with smaller-sized MPs displaying a greater degree of aggregation. MP exposure induces oxidative stress in root tissues, with high concentrations of smaller MPs causing lipid peroxidation. Analysis of the IBR values revealed that C. annuum roots utilize ascorbic acid (ASA) to prevent oxidative damage caused by larger MPs. Conversely, smaller MPs primarily induce superoxide dismutase (SOD) and glutathione (GSH). These results emphasize the significant impact of MP size on plant antioxidant defense response mechanisms, laying the foundation for further investigating the implications for human health.

The toxicity of nanoparticles has attracted much attention, but the toxicity of nanoparticle types to soil fauna remains unclear. In this study, the earthworm (Eisenia fetida) was selected as a representative soil fauna to evaluate the toxicity of nano-hydroxyapatite (n-HAP), -zeolite (n-zeolite), and -iron tetroxide (n-Fe3O4) to soil fauna. The results showed that the skin ultrastructure, mortality, growth, antioxidant systems, and genetic material of the earthworms were affected to varying degrees by different nanoparticles. A filter paper test indicated that dermal exposure to nanoparticles primarily caused lesions in the cuticle, microvilli, and nucleus of the epithelial cells of earthworm skin. Soil incubation experiments showed that all types of nanoparticles could cause weight loss in earthworms, but only n-Fe3O4 resulted in their death. The reactive oxygen species and glutathione contents in earthworms exposed to n-Fe3O4 were much higher than those in earthworms exposed to n-HAP and n-zeolite. All nanoparticles stimulated the catalase and lactate dehydrogenase activity and damaged the DNA of earthworms. Integrated biomarker responses showed that the toxicity to earthworms increased in the following order: n-HAP < n-zeolite < n-Fe3O4. The characterization results indicated that the differences in surface hydroxyl groups and surface charge may be the cause of the differences in toxicity between n-HAP and n-zeolite with similar properties. The highest toxicity of n-Fe3O4 could be due to the size, spherical morphology, positive surface charge and the presence of Fe(II).

Antibiotic contamination has become a global environmental issue of widespread concern, among which oxytetracycline contamination is very severe. In this study, earthworm (Eisenia fetida) was exposed to oxytetracycline to study its impact on the soil environment. The total protein (TP), catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), malondialdehyde (MDA), glutathione S-transferase (GST), and glutathione peroxidase (GPX) oxidative stress indicators in earthworms were measured, and the integrated biomarker response (IBR) approach was used to evaluate the toxic effect of oxytetracycline on earthworms. A Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) and a path analysis model were used to explore the physiological and metabolic processes of earthworms after stress occurs. The results showed that SOD, GPX, and GST play important roles in resisting oxytetracycline stress. In addition, stress injury showed a good dose-effect relationship, and long-term stress from pollutants resulted in the most serious damage to the head tissue of earthworms. These results provide a theoretical basis for understanding the toxic effect of oxytetracycline on soil animals, monitoring the pollution status of oxytetracycline in soil, and conducting ecological security risk assessment.