Distribution Characteristics and Pollution Evaluation of Heavy Metals in Surface Sediments in China’s Largest Freshwater Lake

The spatial distribution characteristics and pollution sources of eight heavy metals Mercury (Hg), Copper (Cu), Lead (Pb), Cadmium (Cd), Zinc (Zn), Arsenic (As), Chromium (Cr) and Nickel (Ni) in the sediments around and within Poyang Lake were studied using the Kriging interpolation method, Pearson correlation analysis, and principal component analysis(PCA). The cumulative characteristics of heavy metals in the study area were analyzed, and risk assessment was conducted using the geo-accumulation, potential ecological risk, and pollution load index methods. The results showed that the average concentrations of Cr, Cu, Ni, Pb, Zn, and Hg in the overall surface sediments of Poyang Lake were 2.26, 5.13, 1.26, 2.46, 1.75, and 1.09 times higher than the background values, respectively, with Cu being the primary pollutant. The geo-accumulation index revealed that the accumulation degree of heavy metals in sediments was in the order of Cu > Pb > Cr > Zn > Cd > Hg > Ni > As. The total potential ecological risk showed that Poyang Lake was at a moderate risk level, with some areas having a slight risk. The pollution load index indicated that Poyang Lake was slightly polluted overall, with some regions experiencing moderate pollution. Spatially, the concentration of heavy metals in sediments was higher in the southern part of the lake, and the spatial distribution of As, Ni, Pb, and Zn concentrations was consistent. The primary sources of As, Cu, Zn, Pb, and Cr were industrial, agricultural, and mineral sources. At the same time, human activities mainly caused Cd and Hg, and Ni was driven primarily by smelting and natural activities.