Sources and Pollution Assessment of Mercury in the Li River System, Guangxi, China

A series of samples included 112 water samples, 40 sediment samples, 40 aquatic plants and 40 near-shore soil samples were collected from the 40 sampling sites in the mainstream and tributaries of the Li River, Guangxi Provence of PR China. The mean value of the total mercury (THg) content in the mainstream of the Li River was found to be 0.12 mu g/L in water, 0.20 mu g/g in bottom mud, 0.032 mu g/g in float grass. The THg mean content in main tributaries of the Li River was 0.15-0.24 mu g/L in water, 0.38-1.7 mu g/g in bottom mud, 0.028-0.044 mu g/g in float grass, which was higher than that in the mainstream. The THg content in river water was correlative with that in bottom mud and float grass and increased from the upstream to the downstream whether in the mainstream or in main tributaries. The THg in the river water in the rainy season was much higher than that in the dry season. These results indicated that the largest sink of Hg contamination of Guilin City was the mainstream of the Li River. According to surface water environment quality standards of China (GB3838-2002), the water Hg level of the Li River satisfied grade IV quality (Hg <= 1 mu g/L)