Heavy Metals, Nitrogen, and Phosphorus in Sediments from the First Drinking Water Reservoir Supplied by Yangtze River in Shanghai, China: Spatial Distribution Characteristics and Pollution Risk Assessment

Abstract

Endogenous pollution is one of the most notable issues in drinking water reservoirs, since the sediment is a main sink of contaminants in the aquatic environment. In this work, we investigated the spatial distribution characteristics of heavy metals and different species of N and P and assessed the pollution risks of the sediments from the Chenhang Reservoir, which is the first drinking water reservoir supplied by Yangtze River in Shanghai, China. The results show that heavy metals, including Cu, Pb, Zn, Mn, and Fe, were mainly accumulated in the downstream, while most Ni and Cr were concentrated in the sediments from the central and western zones. Total N in the sediments was primarily distributed in the eastern reservoir, while ammonia N and most of total P were accumulated in the central and eastern areas. The geo-accumulation index (Igeo) and potential ecological risk index (PERI) suggest that the sediments were polluted by combined heavy metals at minor to medium levels, posing a potential risk to ecosystem. Moreover, sediment quality guidelines (SQGs) indicate that Ni in all sites and Zn in the eastern reservoir would cause great negative biological response to benthic organisms. Additionally, the sediments were slightly polluted by N but not P, especially in the downstream. Multivariate statistical analyses revealed that Cu, Zn, Pb, and N mainly derived from industrial wastewater, domestic sewage and surface runoff from the Yangtze River, while Cr, Ni, and P mainly originated from natural erosion and nonpoint sources.