Ecological Risk Assessment of Cu, Ni, Cd, Hg, Zn, Pb and As in Typical Farmland Gray-Brown Desert Soil in China

Abstract

Heavy metal pollution in soils is a common environmental issue. However, previous studies have primarily investigated the total concentrations of heavy metals, while fraction analysis of heavy metals has rarely been conducted. To bridge this gap, 18 topsoil samples of gray-brown desert farmland soil from the Jinchuan District, Gansu Province, China, were collected to analyze the total concentrations and fractions of Cu, Ni, Cd, Hg, Zn, Pb, and As with the Tessier sequential extraction method that were mainly found in the residual fraction (Pb 50%, As 99%). Ni and Pb were associated with secondary bound to carbonate fractions in most soil samples, while Cd, Hg, and Zn were associated with secondary bound to organic matter fractions. Cu was associated with secondary water-soluble, exchangeable, bound to carbonates, bound to Fe-Mn oxides, and bound to organic matter fractions. The mean values of RAC were in the sequence of Cu > Zn > Cd > Pb > Ni > Hg > As. The results of RSP indicated that the ecological risk levels of Cd, Ni, Cu, Zn, As, and Hg in the soils were low, and Pb was the most significant potential risk factor among all elements. The findings can be used to practice sustainable soil management in the area.