Safe utilization and zoning on natural selenium-rich land resources: a case study of the typical area in Enshi County, China

Selenium (Se) is an essential trace element. However, Se in soil is often accompanied by heavy metals, such as cadmium (Cd), because of geological background. The safe utilization of such Se-rich land resources remains a challenge. A typical Se-rich area located in Enshi County, China, was systematically investigated with geochemical and epidemiological methods. The results show that Se in the topsoil is 0.84 +/- 1.39 mug/g, whereas that of Cd is 0.93 +/- 1.63 mug/g. And the concentration of Se and Cd in corn is 0.22 +/- 0.96 mug/g and 0.15 +/- 0.32 mug/g, respectively, which is mainly related to the high concentrations in soil. The benchmark dose limit of urinary Cd for beta2-microglobulin in subjects (n = 160) was calculated as 3.27 microg/g Cr. In view of crop-human dose effect and combining the relationship among the concentrations of crops and human biomarkers and the concentrations of crops and topsoil, this study established the models of land resource safety zoning. With that, the risk screening value of Cd in the soil could be obtained as 0.98 mug/g in this typical area. The proportions of priority utilization, safe utilization, and strict management of agricultural land area were 58.85%, 22.90%, and 18.25%, respectively, in Enshi, China. These results could provide scientific support for local agricultural development and ecological sustainability.