Spatial risk assessment and sources identification of heavy metals in surface sediments from the Dongting Lake, Middle China

•The Dongting Lake is the second largest freshwater lake in China.•Heavy metals in surface sediments from the lake were sampled and measured.•The south and east lake parts were higher polluted based on spatial risk mapping.•Cd, Hg and As were the priority pollutants in the sediments based on SQGs and PER.•Three source groups were identified based on multivariate statistical methods.

Surface sediment (0–10 cm) samples were collected from 12 typical sites throughout the Dongting Lake. Samples were detected by inductively coupled plasma–mass spectrometry and atomic fluorescence spectrometry for Cr, Cu, Zn, Pb, Cd, As, and Hg, respectively. Based on geostatistics analyses, generally distributions of these heavy metal contents except that of Hg decreased in the order of the South Dongting Lake > the East Dongting Lake > the outlet of Dongting Lake ≈ the West Dongting Lake. Sediment quality guidelines (SQGs) and Hakanson's method were used to determine potential risk of heavy metal contamination. The results indicated that the mean contents of As and Cd exceeded the probable effect level (PEL), and there were 58% for Cd and 50% for As out of all sampling sites exceeding PEL. The calculated mean potential ecological risk degrees were in the descending order of Cd, Hg, As, Pb, Cu, Cr and Zn. Besides, multivariate statistical analyses revealed that Zn, Pb, Cd and As mainly originated from mining wastewater and industrial wastewater which were probably in the close relationship with characteristics about the Yueyang city and the Xiangjiang River. Cr and Cu mainly derived from natural erosion and nonpoint agricultural sources. However, Hg originated from both sources. Cluster analysis indicated that Cluster 1, S5, S6 and S10 included, were probably taken as the higher polluted sites, and Cluster 2, S7, S9 and S11 included, might be explained as the moderate pollution regions.