Compositional analysis of typical selenium ore from Enshi and its effect on selenium enrichment in wetland and dryland crops

Abstract

The objectives of this study were to determine the valence state of Se and major components in Se ore powder, examine its effect on Se enrichment in crops under different cultivation patterns, and assess the safety of edible parts of crops. Se ore powder from Enshi was subjected to compositional analysis by X-ray photoelectron spectroscopy and applied to rice (wetland) and soybean (dryland) fields before planting. Se was mainly present in tetravalent and zero-valent forms at a 4:6 ratio in Se ore powder. Following soil application of Se ore powder, concentrations of As, Hg, Cr, and Pb in brown rice and soybean seed were below the limit of detection, and the Cd concentration was below the European Union food regulation limit. Organic Se accounted for more than 96% of total Se in both crops, including >91% Se-methionine. Compared with dryland, the flooded environment facilitated residual Se transformation into Fe/Mn oxide-bound Se, and thus increased the potential activity of Se in the soil. Se ore powder can be applied for the production of Se-rich agricultural products in the short-term, and possibilities of upgrading the Se ore product should be considered in the future.