Accumulation of thallium and potential toxic elements in a water-soil-rice system from a pyrite mining area, southern China: Source apportionment and health risk assessment

Abstract

Contamination of heavy metals in the arable soil around mining areas has become a hot issue of global concern, relating to food security and human health risks. This study investigates the accumulation of thallium (Tl) and six other potential toxic elements (PTEs) (Pb, Cu, Cd, As, Ni, Zn) in irrigation water, rhizosphere soil, and corresponding rice grain samples collected from the region downstream of pyrite mining areas, southern China. Surface water in this area might be under the influence of sewage discharge from pyrite mines, with irrigation water exhibiting elevated Tl, Cd, and Zn contents of 26.22, 10.43, and 18,275 μg/L respectively. As a result, 67 %, 78 % and 44 % of rice samples exceeded food safety standards for As, Pb, and Cd respectively. Positive matrix factorization (PMF) modeling revealed that, irrigation activities account for 27.1 % target contaminates accumulation in paddy lands. Although the Tl concentrations in rice grains were relatively low (ranging from 0.01 to 0.06 mg/kg), the substantial consumption of rice, as the staple food, posed significant health risks for local residents (HQ > 16 for adults and > 12 for children, respectively). This study provides a theoretical basis for understating the contribution of irrigation to PTEs contamination in paddy fields in downstream mining-affecting regions. These findings are crucial for developing strategies to mitigate heavy metals contamination, selecting appropriate soil remediation methods, and reducing ecological and health risks.