Comprehensive Study of Lead Speciation and Its Bioavailability in Soils From a Lead/Zinc Mining Area by Micro X-Ray Fluorescence and X-Ray Absorption Near-Edge Structure

Abstract

Lead species significantly influences its mobility and bioavailability. In this study, improved BCR procedure, laboratory culture, laboratory micro X-ray fluorescence (μ-XRF), and synchrotron radiation X-ray absorption near-edge structure (XANES) were used to investigate the distribution, speciation, and bioavailability of Pb in soils from a Pb/zinc (Zn) mining area contaminated with heavy metals. The results showed that ① Pb was mainly distributed in the reducible[which binds to oxides of iron (Fe) and manganese (Mn)], acid soluble, residual, and oxidizable fractions, ② Pb content in plant tissues correlated with acid-soluble Pb content in soil, ③ μ-XRF results indicated that Pb was distributed heterogeneously, and correlated with the hot spot with high concentration of Mn. In some area, Pb also correlated with Fe, and ④ Pb was predominantly present as Pb-goethite (41%-46%), Pb3(PO4)2(36%-55%), and Pb-MnO2(3%-24%) in soil samples. The results of this study showed that oxides of Fe and Mn, and Pb3(PO4)2precipitate mainly comprise the pool of Pb in soils.