Potential Ecological Risk Assessment of Heavy Metals in River Sediments of Drinking Water Sources of Huangpu River

The upper streams of the Huangpu River is an important drinking water source area for Shanghai. To better characterize heavy metal pollution of the region, samples of sediments were collected from 15 sampling points distributed in the main stream and major tributaries of the Huangpu River for analysis of Cu, Pb, Cd, Hg and Zn contents and for ecological risk assessment. It was found that all the five heavy metals, with Cd and Hg in particular, in the 15 samples exceeded the medians of their respective environment background values by a varying extent, and only Cu and Cd exceeded their respective highest background values. Ecological risk assessment using the potential ecological risk index method and the pollution load index method shows that the ecological risks of the heavy metals in the study area could be sorted as “no pollution” or “moderate pollution”, and Sampling Point #1, #5, #9, #11, #12 and #13 were comparatively high in ecological risk. Cd and Hg are the two dominant ecological risk contributors in the study area. It is noteworthy that some of the tributaries, like Dazhenggang and Yuanxiejing, were, on the whole, higher than the main stream in ecological risk. Generally speaking, heavy metal pollution in river sediments of the upper streams of the Huangpu River is still lower than the “medium level”.