Spatial Distribution, Sources and Bioavailability of Heavy Metals in the Surface Sediments of Longjiang River, Southern China

Abstract

In order to evaluate the pollution status, possible sources, and bioavailability of heavy metals (As, Cd, Pb, Sb, Zn, and Tl), 33 surface sediments were collected from Longjiang River, Southern China. The total concentrations and potential bioavailable concentrations of the heavy metals were analyzed using ICP-MS. Enrichment factors (EFs), Pearson correlation analysis, and principal component analysis (PCA) were used to further assess their pollution degree and potential sources. Results showed that the surface sediments of Longjiang River have been suffering heavy metal (As, Cd, Pb, Sb, and Zn) pollution to different degrees. The maximum concentrations of As, Cd, Pb, Sb, and Zn were 67.0, 7.42, 227, 229, and 807 mg·kg-1, respectively, while the Tl concentration were very low, with little variation. Moreover, the polluted sites were mostly located in the mid-lower of the main stem and in tributaries (Dongxioajiang and downstream of Dahuanjiang), and the pollution degree of the heavy metals, in a descending order, were Cd > Sb > Zn > Pb > As > Tl. Pearson correlation analysis and PCA indicated that As, Cd, Pb, Sb, and Zn predominantly originated from anthropogenic inputs, including nonferrous metal mining and smelting, municipal sewage, and agricultural activities, and Tl mostly derived from natural rock weathering. The bioavailability of heavy metals in the sediments tended to be controlled by their sources. The percentages of bioavailable heavy metals (As, Cd, Pb, Sb, and Zn) in the highly anthropogenic impacted areas (the mid-lower of the main stem and downstream of Dongxiaojiang tributary) were also high, with the average percentages of bioavailable As, Cd, Pb, Sb, and Zn of 26%, 51%, 49%, 38%, and 47%, respectively. High EF values and high bioavailable percentages of heavy metals easily and greatly cause high ecological risk of Longjiang River.