Spatial distribution and ecological risk assessment of heavy metal pollution in surface sediments from shallow lakes in East China

Abstract The rapid industrialization and urbanization that have occurred in East China in recent decades pose a threat to the local aquatic ecosystem. Pollution by heavy metals is one of the factors that threaten the environment, and assessing the risk of heavy metals is essential for promoting proper freshwater management in aquatic ecosystems. In this study, 121 surface sediment samples were collected from 63 shallow freshwater lakes in the middle and lower reaches of the Yangtze and Huai River Basins (MLYHB) to study the spatial distribution of common heavy metals, including As, Cd, Cr, Cu, Ni, Pb, and Zn. Multivariate statistical analysis, which based on the metals' distribution and geoaccumulation index (Igeo), sediment quality guidelines (SQGs), potential ecological risk (PER) index, and risk index (RI), was conducted to elucidate the pollution source and evaluate the potential ecological risks. The average concentrations of As, Cd, Cr, Cu, Ni, Pb, and Zn in the surface sediments were 22.6, 1.1, 74.6, 47.6, 38.3, 37.3, and 141.9 mg/kg, respectively. The concentrations of these metals in the surface sediments from the middle reaches were generally higher than those in sediments from the lower reaches of MLYHB. The concentrations of Cr and Ni were similar to the background values, and they mostly originated from natural detritus. Cd pollution was predominant in MLYHB, and the Zn, Cd, Cu, and Pb in the surface sediments mainly originated from industrial and agricultural activities, while As originated from pollution due to coal combustion. According to the SQGs and PER, Cr, Cu, Ni, Pb, and Zn likely pose a low ecological risk, while As and Cd were identified as the priority pollutants by the two methods, respectively, and may pose a high ecological risk to the aquatic ecosystem in MLYHB. Moreover, the PER of heavy metals in surface sediments is more severe in the middle reaches of MLYHB than that in the lower reaches. The middle reaches of MLYHB should be the priority regions for environmental monitoring and management.