Bioaccumulation and Health Risk Assessment of Heavy Metals in the Soil-Rice System in a Typical Seleniferous Area in Central China

Heavy metals are rich in seleniferous areas; however, the bioaccumulation and health risk of heavy metals are poorly understood, given the fact that selenium (Se) can inhibit the phytotoxicity and bioavailability of many heavy metals. The present study investigated the bioaccumulation of heavy metals in the soil-rice system in the Enshi seleniferous area of central China. Soils were contaminated by Mo, Cu, As, Sb, Zn, Cd, Tl, and Hg caused by the weathering of Se-rich shales. Among these heavy metals, Cd and Mo had the highest bioavailability in soils. The bioavailable fractions of Cd and Mo accounted for 41.84 and 10.75% of the total Cd and Mo in soils, respectively. Correspondingly, much higher bioaccumulation factors (BAFs) of Cd (0.34) and Mo (0.46) were found in rice, compared with those of other heavy metals (Zn 0.16, Cu 0.05, Hg 0.04, and Sb 0.0002). For the first time-to our knowledge-we showed that the uptake of Hg, Cd, and Cu by rice could be inhibited by the presence of Se in the soil. The probable daily intake (PDI) of Se, Cd, Mo, Zn, and Cu through consumption of local rice was 252 +/- 184, 314 +/- 301, and 1774 +/- 1326 mu g/d; and 7.4 +/- 1.68 and 0.87 +/- 0.35 mg/d, respectively. The high hazard quotients (HQs) of Mo (1.97 +/- 1.47) and Cd (5.22 +/- 5.02) suggested a high risk of Cd and Mo for Enshi residents through consumption of rice. Environ Toxicol Chem 2019;38:1577-1584. (c) 2019 SETA