Combined toxicity of soil antimony and cadmium on earthworm Eisenia fetida: Accumulation, biomarker responses and joint effect

Antimony (Sb) and cadmium (Cd) coexisted in urban contaminated soil due to textile printing and dyeing waste water, but the environmental risks and ecotoxicological effects they caused are poorly understood. In this study, earthworm Eisenia fetida was exposed into soil spiked with Sb, Cd and their mixture, and multiple biomarker responses (protein, malonaldehyde (MDA), metallothionein (MT), reactive oxygen species (ROS), catalase (CAT), superoxide dismutase (SOD), peroxidase (POD) and glutathione S-transferasesase (GST)) were measured to evaluate biological health status and joint effect via Biomarker rResponse Index (BRI) and Effect Addition Index (EAI). The results showed that earthworm could not accumulate Sb effectively, but Cd accumulation by earthworm indicated a well dose-response relationship between issue content and treatment level. Secondly, the protein content was overall decreased, and the contents of MDA, MT and ROS as well as the activities of SOD, POD, CAT, GST and ROS were increased, suggesting membrane lipid peroxidation and waken-up antioxidant capacity, among which GST was the most sensitive. Furthermore, severe alterations for health status were always found except under the antimony dosage of 5 mg/kg, and earthworm health status was more sensitive in presence of single Cd. According to EAI, a clear joint effect of antagonism was observed at whole range of combined treatment levels. This is a key study providing biomarker responses of soil Sb and evaluating the joint effect of Sb and Cd at different contents using earthworm Eisenia fetida, BRI and EAI.