Environmental Risk Assessment and Regulatory Rating of Water Sources along the Yangtze River’s Nanjing Section under the Influence of Multiple Risk Sources

Abstract

To complement the current studies of risk assessment on water sources which seldom consider the distribution effects of multiple risk sources concentration, and improve the efficiency of water source supervision, this study establishes a method system for risk assessment of water sources and regulatory rating evaluation under the distribution effects of multiple risk sources concentration. The method system includes: (1) utilizing the single-risk source impact index to characterize the risk impact degree of the single-risk source on the water source, the index calculation method of single-risk source impact considers the risk degree and the distribution location of risk source; (2) using the multiple risk sources impact index to characterize the risk impact degree of the multiple risk sources on the water source, the index calculation method of multiple risk sources considers the impact index of single-risk source, the number of risk sources, and the distribution concentration of multiple risk sources; (3) the environmental risk assessment and regulatory rating evaluation method consider multiple risk sources impact index, anti-risk ability of water source, and the importance of water source. This method system has been applied to the environmental risk assessment and regulatory rating of eight water sources along the Nanjing Yangtze River, with excellent achievements. As the results reveal, eight water sources suffer 437 risk impacts from 175 risk sources, 69.04% of which are low-risk impacts and 13 are high-risk impacts. Longtan water source suffers the most risk impacts of 86, among which eight are high-risk impacts. The impacts of multiply-risk sources on the eight water sources are high-risk impacts. The impact index of multiple risk sources increases from the upstream water sources to the downstream water sources, reaching the maximum value of 5.267 at the most downstream Longtan water source. Though the environmental risk and supervision rating of Longtan water source is high, those of other water sources are rated as medium.