Ecological Risk Assessment of Nonylphenol in Surface Waters of the Yangtze River Delta Based on Species Sensitivity Distribution Model

Nonylphenol (NP) is a typical type of persistent organic pollutants (POPs) with endocrine-disrupting effect. Its ecological risk has caused increasing concerns owing to its degradation-resistance, bioaccumulation, and widespread distribution in the environment. The species sensitivity distribution (SSD) method has been widely used for establishing water quality criteria (WQC) and performing ecological risk assessment (ERA) of the water environment. However, the selected sensitive species may exhibit different toxicity sensitivity in different geographical regions, which would affect the results of WQC and ERA. In this study, SSD was applied to calculate the predicted no effect concentrations (PNECs) based on the acute and chronic toxicity data of the general sensitive species and native sensitive species in China. The results showed that there was little difference between the PNECs derived from the general sensitive species and native sensitive species based on the acute toxicity data, which indicated that the sensitivity of native species towards the acute toxicity effect of NP is similar to that of general species. However, the PNECs based on the chronic toxicity data were quite different, and the Chinese native species appeared to be more sensitive than general species to the chronic toxicity effect of NP. As a result, direct use of the PNECs derived from non-local species may lead to insufficient protection of Chinese native species. Based on the PNECs derived from the acute and chronic toxicity data, the risk quotient (RQ) method was used to characterize the ecological risk of NP in the surface waters of Yangtze River Delta. The results showed that the RQ based on PNECs derived from the acute data and chronic data of general sensitive species may lead to an underestimation of the ecological risk. The mean RQ values based on the PNECs derived from the chronic data of Chinese native sensitive species ranged from 0.23 to 1.55. Luoma Lake was found at a high risk, and the maximum RQ values of Taihu Lake and Yangtze River (Nanjing) exceeded 1, indicating the high risk of the individual areas which deserve further attentions. In conclusion, the chronic toxic effect of NP on Chinese native aquatic organisms can be identified, and continuous attention should be paid to the long-term adverse effect of NP, for which actions should be taken to ensure the health of the aquatic ecosystem.