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

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.

[Spatial Distribution Characteristics and Potential Ecological Risk of Antimony and Selected Heavy Metals in Sediments of Duliujiang River].

In order to investigate the spatial distribution characteristics of Sb and selected heavy metals, and to discriminate their sources and potential ecological risks in surface sediments of the Duliujiang river,a total of 62 surface sediment samples were collected in this study. Total contents of Sb, As, Cd, Co, Cr, Cu, Mo, Ni, Pb, Tl, Zn and Fe in these samples were measured by inductively coupled plasma mass spectrometry(ICP-MS) and the inductive plasma optical emission spectrometry(ICP-OES). Principal component analysis(PCA) and Pearson correlation analysis were used to deduce the potential sources of these elements. Geo-accumulation index(Igeo), enrichment factor(EF) and Hakanson's potential ecological risk index(Eri and RI) were calculated to evaluate the pollution degree of heavy metals in sediments. The results indicated that the contents of heavy metals in sediments were impacted by human activities to different extents, and the Duliujiang River was significantly contaminated by Sb. The contents of Sb in sediments reached up to 7080 mg·kg-1, and gradually decreased from upstream to downstream, while the contents of As, Cd, Co, Cr, Cu, Mo, Ni, Pb, Tl and Zn varied indistinctively. The PCA results showed that the cumulative proportion of the first two components accounted for 77.67% of the total variables, suggesting that two major sources of Sb and other heavy metals were mining/smelting industry and natural sources. The calculated Igeo and EFs also showed that the surface sediments of the Duliujiang River were majorly polluted by Sb, followed by As and Co, lightly contaminated with Co, Cu, Mo, Ni, Pb and Tl, and uncontaminated with Cr. The ecological hazards(Eri) for each metals in a descending order were Sb > Cd > As > Co > Ni > Pb > Cu > Zn > Cr. The comprehensive index of potential ecological risks(RI) for heavy metals indicated that 58.1% of the 62 sediments samples had more than moderate ecological risks, and the sites with high RIs were generally located around Sb mining area and the downstream of the Baluo River. In addition, the Eri of Sb was a predominant component of RI, indicating that the Duliujiang River is an area with extremely high potential ecological risk of Sb.