Combined toxic effects of arsenic and molybdenum disulfide nanomaterials on earthworms (Eisenia fetida)

Abstract

With the increasing release of nanomaterials into soil ecosystems, the intensity of combined exposure to nanomaterials and metalloids/heavy metals are rising, highlighting the urgent need to understand their joint toxicological effects of nanomaterials and metalloids/heavy metals. In this study, the ecotoxicological impacts of the co-exposure of molybdenum disulfide nanomaterials (MoS₂ NMs) and the metalloid arsenic (As) in soil are explored. Specifically, a pot experiment was conducted to investigate the toxic effects of combined exposure to As (25, 50, and 100 mg kg⁻¹ soil) and MoS₂ NMs (30 mg kg⁻¹ soil) on earthworms. Key parameters including earthworm growth, bioconcentration, physiological and biochemical responses, and gut microbial metabolism were assessed. Soil and earthworm samples were collected on the days 7, 14, and 28 post-treatment. The results revealed that the co-exposure of MoS₂ NMs and As increased the As accumulation in earthworms by 16.3%, 26.7%, and 12.4%, and reduced their body weights by 39.5%, 34.9%, and 28.1%, respectively, compared to the single exposure of As. This co-exposure aggravated pathological damage, elevated oxidative stress, and significantly increased the integrated biomarker response index. Furthermore, it disrupted the balance of gut flora and metabolic pathways in earthworms and enhanced their toxicity. This study provides new insights for evaluating the ecological and health risks associated with the simultaneous presence of nanomaterials and metalloids/heavy metals in soil environments.