Calculation and application of Sb toxicity coefficient for potential ecological risk assessment

The potential ecological risk index (RI) is a diagnostic tool for pollution control which integrate the concentration of heavy metals with ecological effect, environmental effect and toxicity. However, the lack of toxicity coefficients for specific heavy metals limits its widespread use. In this study, we calculated the toxicity coefficient (=7) for antimony (Sb) based on Hakanson's principles, thus broadening the range of potential applications of this risk assessment tool. Taking the case of Xikuangshan (XKS), the largest Sb mine in the world, we predicted the potential ecological risk factor (E_rⁱ) of Sb for sediment and soil. This was then compared with the enrichment factor (EF) and index of geoaccumulation (I_geo). Results showed that Sb shared the similar pollution categories regardless of E_rⁱ, EF or I_geo indexes was used indicating the appropriateness of the determined toxicity coefficient. Regression analysis results further demonstrated that E_rⁱ was in agreement with bioavailable concentrations (Diffusive Gradient in Thin Films and Community Bureau of Reference extraction concentrations), particularly in sediments. This means that E_rⁱ is a reliable and logical index for evaluating Sb pollution in sediments within aquatic environments and in soils within terrestrial environments.