[Comparison of Heavy Metal Contamination Characteristics in Surface Water in Different Functional Areas: A Case Study of Ningbo]

From industrial and commercial areas of Ningbo City, China, 85 surface water samples were collected. The concentrations of six heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) in the samples were measured, and the characteristics of the spatial distributions of those metals were analyzed. Through a combination of regional characteristics and Pearson correlation coefficients of the different heavy metals, the main pollution sources of the two areas were analyzed. The potential ecological risks of these heavy metals were evaluated by considering health risk and cancer risk indices. The results indicate that the heavy metal pollution of surface waters was serious in both the industrial and commercial areas. Furthermore, the differences between the two areas were also observed. In the industrial area, the average concentrations of the six heavy metals were, from highest to lowest, in the order: Zn >>Ni>Pb> Cr> Cu> Cd, and the main sources were industrial emissions. Four heavy metal concentrations exceeded the national environmental standard, which, from highest to lowest, were in the order: Cd> Pb> Cr >>Zn. In the commercial area, the average concentrations, from highest to lowest, were in the order: Cr> Pb >>Zn> Ni> Cd> Cu, and the main sources were road pollutants. Three heavy metal concentrations exceeded the national standard, and the order, from highest to lowest, was Cd> Pb>>Cr, with Cd and Pb having the most potential health risk. In both the industrial and commercial areas, there were some potential health risks and high carcinogenic risks. Cd, Cr, and Pb have the highest potential health risks, whereas Cr is the major potentially carcinogenic metal. The commercial area had 1.7 times the potential carcinogenic risk as that of the industrial area. The government should pay more attention to heavy metal pollution of surface waters in Ningbo City, China.