Cadmium transfer from tungsten mining and refining to soil, plants, and humans: Geochemical baseline and...

Tungsten (W) mining and refining pose environmental contamination and health risks. W mine in Dayu County, Jiangxi Province, China, is one of the largest W deposits worldwide and has been active since 1908. This study explores the accumulation of Cadmium (Cd) in soil and sediment, its enrichment in plants, and the health risks to humans in the surrounding and downstream areas of W mining and refining. Soil, sediment, plant, river and ground water, wastewater, and solid wastes from W mining and refining were sampled and analyzed for Cd. The results showed that Cd levels were 0.06-3.47 mg/kg in soil, 0.09-10.16 mg/kg in sediment, 0.003-20.6 mg/kg dry weight (dw) in plants, 0.09-13 μg/L in river water, 0.13-0.53 μg/L in groundwater, 0.21-120 μg/L in wastewater, and 0.03-162 mg/kg in solid waste. A geochemical baseline for Cd was developed, showing average anthropogenic Cd concentrations of 0.24 and 2.29 mg/kg in the soil and sediment, respectively. Cd mobility generally decreased from soil to roots, roots to shoots, and shoots to edible parts. Citrus fruits contained the lowest Cd, which was generally two orders of magnitude lower than that in other plants. The non-carcinogenic hazard quotients of Cd exposure via soil, water, vegetable, rice, and fruit ingestion were >1 at 0.37-0.63 and 0.41-0.68 probabilities for local adults and children, respectively, depending on percentage of home-grown food ingestion out of the total food ingestion. These risk probabilities were further tested using the urinary Cd concentration of individuals in Dayu County, where the urinary Cd level of approximately 68% of adults was over 5 μg/g creatinine, according to the World Health Organization. Ingestion of home-grown rice and vegetables was the major source of Cd exposure for local residents, which accounted for almost all health risks associated with Cd exposure. It is suggested that citrus can be largely planted in the area for the phytostabilization of Cd-contaminated soil, control of Cd health risk, and fruit production.