The biochemical and toxicological responses of earthworm (Eisenia fetida) following exposure to nanoscale zerovalent iron in a soil system.

Nanomaterials have increasingly gained a great amount of interest due to their widespread applications, while their potential impacts on invertebrates in soil lack thorough investigation. This study is mainly aimed at determining the acute and subacute toxicity to the earthworm Eisenia fetida, induced by different levels of nanoscale zerovalent iron (nZVI) (100, 500, 1000 mg kg-1) in natural soils. The results showed that compared to the controls, exposure to 500 and 1000 mg kg-1 of nZVI significantly (P < 0.05) inhibited growth and respiration and increased avoidance response in earthworms. The perturbations of antioxidant enzyme activities (superoxide dismutase-SOD and catalase-CAT), malondialdehyde (MDA) content, and reactive oxygen species (ROS) clearly revealed that oxidative stress was induced in E. fetida exposed to nZVI. Good correlations were observed in current results among the growth, respiration, MDA, and ROS (R > 0.8; P < 0.05), and that ROS was the most sensitive parameter in response to the stress caused by nZVI. Additionally, the histopathological examination of transverse sections of the exposed earthworms passing through the body wall illustrated that there was a serious injury in epidermal tissue after an exposure of 28 days. These findings will provide a comprehensive understanding of toxicological effects of nZVI in a soil-earthworm system.