Detection and Health Risk Assessment of Heavy Metals in Upper Water of Nansi Lake, China

Nansi Lake, China, has an economically valuable aquaculture industry but fish kills caused by heavy metal pollution have been problematic in recent years. Freshwater supply is critical for centers of industrial activity, commerce, and residences, but growing urban populations pollute the water they rely on. In the case of Nansi Lake, China, there are concerns that continuing urban growth is contributing to heavy metal pollution of the lake water, with potential economic and health impacts, but the extent of this pollution is unclear. To thoroughly understand the spatiotemporal characteristics of heavy metal pollution in Nansi Lake, China, we measured the concentrations of six heavy metals in upper water from 18 sites distributed across four sub-lakes of Nansi Lake and performed a health risk assessment over four seasons. The average concentrations of Pb, Cd, and Hg exceeded those of tertiary water quality standards and were 3.18-, 4.16-, and 14-fold higher than the values listed in the national surface water quality standard of China (GB3838-2002), respectively. Meanwhile, Cu, Mn, and Zn concentrations did not exceed the values in these standards. The heavy metals generally had consistent seasonal distribution patterns in different lake areas, but these patterns differed among the heavy metals, indicating that the metals may have different sources or transformation patterns. The full-year risk value of non-carcinogens in Nansi Lake was 2.32 x 10-6 a-1, which was lower than the maximum acceptable risk level (5 x 10-5 a-1) specified by the International Commission on Radiological Protection, implying that these was no harm to human health from these carcinogens. However, the full-year risk value of the carcinogen Cd was 22.54 x 10-5 a-1, which was much higher than the maximum acceptable level; this risk value contributed to 98.98% of the total risk and requires further attention.