Selenium (Se) speciation in soil is critically important for understanding the solubility, mobility, bioavailability, and toxicity of Se in the environment. In this study, Se fractionation and chemical speciation in agricultural soils from seleniferous areas were investigated using the elaborate sequential extraction and X-ray absorption near-edge structure (XANES) spectroscopy. The speciation results quantified by XANES technique generally agreed with those obtained by sequential extraction, and the combination of both approaches can reliably characterize Se speciation in soils. Results showed that dominant organic Se (56-81% of the total Se) and lesser Se(IV) (19-44%) were observed in seleniferous agricultural soils. A significant decrease in the proportion of organic Se to the total Se was found in different types of soil, i.e., paddy soil (81%) > uncultivated soil (69-73%) > upland soil (56-63%), while that of Se(IV) presented an inverse tendency. This suggests that Se speciation in agricultural soils can be significantly influenced by different cropping systems. Organic Se in seleniferous agricultural soils was probably derived from plant litter, which provides a significant insight for phytoremediation in Se-laden ecosystems and biofortification in Se-deficient areas. Furthermore, elevated organic Se in soils could result in higher Se accumulation in crops and further potential chronic Se toxicity to local residents in seleniferous areas. (C) 2017 Elsevier Ltd. All rights reserved. Publication name | ENVIRONMENTAL POLLUTION, 225 361-369; 10.1016/j.envpol.2017.02.062 JUN 2017 | Author(s) | Qin, Hai-Bo; Zhu, Jian-Ming; Lin, Zhi-Qing; Xu, Wen-Po; Tan, De-Can; Zheng, Li-Rong; Takahashi, Yoshio | Corresponding author(s) | QIN Haibo qinhaibo@vip.gyig.ac.cn -Chinese Acad Sci, Inst Geochem, State Key Lab Environm Geochem, 99 Lincheng Rd West, Guiyang 550081, Peoples R China -Univ Tokyo, Grad Sch Sci, Dept Earth & Planetary Sci, Bunkyo Ku, Hongo 7-3-1, Tokyo 1130033, Japan ZHU Jianming jmzhu@cugb.edu.cn China Univ Geosci, State Key Lab Geol Proc & Mineral Resources, 29 Xueyuan Rd, Beijing 100083, Peoples R China. | View here for the details
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