Assessment of Heavy Metal Pollution and Human Health Risk of Surface Waters in the City of Ningbo, China

Abstract

In order to evaluate the present situation and the potential ecological risk of heavy metal pollution in the surface waters of eastern Chinese coastal cities, the city of Ningbo was used as an example. From surface waters in Ningbo, 255 water samples were collected. The concentrations of six heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) were measured for the samples. The potential ecological risk of these heavy metals was evaluated by calculating health risk and cancer risk indices. The results indicate that, in the surface waters of Ningbo, the average concentrations of the six heavy metals were in the increasing order of Zn > Pb > Cr > Ni > Cd > Cu. Three of the heavy metal concentrations exceeded the national environmental quality standards for surface water (GB 3838-2002, grade Ⅴ), and the order of exceeding the standard:Cd > Pb > Cr. Electroplating wastewater, metal waste produced, traffic pollutant, dyes, and coatings waste were the main pollutant sources. There were some potential health risks in over 70 percent of the surface waters in Ningbo, and the surface waters of the Zhenhai and Haishu districts had the highest potential health risk. There were three major potential health risk heavy metals, and their order of increasing risk was Cd > Cr > Pb. For adults and juveniles, the average carcinogenic risk indices were 17600 and 24800 times the critical values, respectively. Moreover, over 95 percent of the risks were attributed to Cr. The potential carcinogenic risk index of commercial areas with dense population was nearly 2 times that of the city average. The results indicated that the state of heavy metal pollution in the surface waters of Ningbo was very serious, thus the government should pay more attention to this issue.