FANG Minwen1, WANG Cheng1,*, XIONG Yinghan1, ZHAO Yanping2, ZHONG Cong3, XIE Mingjie1

（1. School of Environmental Science and Engineering, Changwang School of Honors, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Nanjing University of Information Science and Technology, Nanjing, 210044, China; 

2. Guangdong Provincial Key Laboratory of Chemical Measurement and Emergency Test Technology, Insititute of Analysis, Guangdong Academy of Sciences (China National Analytical Center, Guangzhou), Guangzhou 510070, China; 

3. Key Laboratory of Environment Change and Resources Use in Beibu Gulf, Ministry of Education, Nanning Normal University, Nanning 530001, China）

Abstract：In order to explore the migration of lead (Pb) and the contribution of human activities to Pb in the soil, we collected the samples from two soil profiles at the hillside and piedmont of Baohua Mountain, which is located in the vicinity of a Pb-Zn mine from the Ning-Zheng area. By using the chemical sequential extraction and Pb isotopic fingerprint, the transformation of Pb in the soil profiles were investigated and the anthropogenic contribution of Pb were quantified. The results show that the mining activities lad to a marked Pb enrichment in the topsoil with the concentration of 2.9-7.7 μg/g higher than the local background. The exogenous Pb in the topsoil transported downward via the particle migration and leaching, and the migration mainly occurred at the layer of 10-25 cm. The maximum migration distance of Pb at the piedmont increased by 5 cm compared to that at the hillside. Pb in the soil were mainly bound to the residual, iron/manganese oxides, and subordinately, bound to carbonates and humid. Compared to the soil at the hillside, the soil at the piedmont were observed with significantly lower concentrations of Pb bound to carbonates, humid fraction Pb and exchangeable fraction Pb, respectively, but higher concentration of Pb bound to iron/manganese oxides. Part of Pb bound to carbonates and humid in the topsoil resolved and moved into the deeper soil, in where was fixed by iron/manganese oxides. The Pb isotopic fingerprinting pinpoints that approximately 17.1% of Pb in the forest topsoil (0-5 cm) at the hillside were sourced from the Pb-Zn ore mining activity, and the contribution of anthropogenic activity on Pb concentration deceased with the increasing soil depth (< 3% at 15-20 cm), implies that the exogenous Pb had moved down no more than 30 cm. Due to the eluviation, the contribution rate of anthropogenic source on the Pb in the topsoil (0-5 cm) at the piedmont was obviously lower than that at the hillside, and the contribution rate of anthropogenic source on the Pb in the other layers at the piedmont were similar, show no evident descend with the depth increases. The Pb isotopic fingerprinting and high-resolution sampling on soil profile can quantify the influence of anthropogenic activity on the metal in the environment, and also offer the scientific basis for environmental management.

Key words：heavy metals; pollution source; Yangtze River delta; soil profile; lead isotopes; fractionations

EARTH AND ENVIRONMENT Vol.51, No.2, Tot No.352, 2023, Page 235