Bioaccessibility of antimony and arsenic in highly polluted soils of the mine area and health risk assessment associated with oral ingestion exposure

• Concentrations of Sb and As were measured in soils from the largest Sb mine in China, Xikuangshan Sb mine.
• Bioaccessibility of Sb and As were compared using two commonly used in vitro extraction methods (SBET and PBET).
• The bioaccessible Sb and As were mainly affected by total concentrations, Fe, Al, Mn and organic matter (OM) contents in the soils.
• Considering the Sb and As bioaccessibility can provide more applicable guidelines for risk assessments.

In this study, the bioaccessibility and the human health risks of Sb and As in soils from Xikuangshan (XKS) Sb mine, Hunan, China were investigated using two commonly used in vitro extraction methods, Simplified Bioaccessibility Extraction Test (SBET) and Physiologically Based Extraction Test (PBET). Soils in the XKS Sb mine area were mainly co-contaminated by Sb (74.2–16,389; mean: 3061 mg kg−1) and As (7.40–596; mean: 216 mg kg−1). The bioaccessibility values of Sb and As in most cases were less than 30%, and the average bioaccessibility values of Sb and As were 5.89±6.44% and 2.13±2.55% for the SBET extraction; 7.83±9.82% and 6.62±6.37% for the PBET (Gastric) extraction; and 3.03±3.53% and 2.40±2.01% for the PBET (Intestinal) extraction, respectively. The bioaccessible Sb and As were significantly positively correlated with the total concentrations, but negatively correlated with the Fe, Al, Mn and organic matter (OM) contents in soils. Risk assessment results based on total concentrations might overestimate the risk existing in the studied area. After considering the bioaccessibility, the Hazard Quotient (HQ) values of Sb for most of the sampling sites and of As for all of the sampling sites became lower than 1. The Carcinogenic Risk (CR) values of As were also significantly reduced, 8.77E−06 and 1.74E−05 on average for the SBET and PBET methods, respectively. Considering the bioaccessibility can provide more applicable guidelines for risk assessments and more rational suggestions in the management of the soils contaminated with Sb and As.