Screening of high phytotoxicity priority pollutants and their ecological risk assessment in China's surface waters

The protection of aquatic plants has received less attention in ecological risk assessment of pollutants compared with animals. Some pollutants like herbicide, however, are more toxic to aquatic plants than to animals. Aquatic toxicity data of 126 priority pollutants were screened and analyzed in this study. Through data analysis, five priority pollutants namely 1,1,1-trichloroethane (1,1,1-TCA), 4-nitrophenol (4-NP), butylbenzyl phthalate (BBP), di-n-butyl phthalate (DBP) and N-nitrosodimethylamine (NDMA) were identified to have high phytotoxicity effect. The most sensitive aquatic plants to these five pollutants are all alage, including Chlamydomonas reinhardtii, Pseudokirchneriella subcapitata, Gymnodinium breve. The water quality criteria concentration of the five pollutants were derived by the species sensitivity distribution method. The acute criteria concentration for the five pollutants were derived to be 1474, 2180, 54.41, 98.52 and 520.4 μg L(-1), and the chronic criteria concentration for them were 147.4, 218.0, 5.441, 9.852 and 52.04 μg L(-1), respectively. For China's freshwater bodies, the results of ecological risk assessment based on the derived criteria showed that, for the selected pollutants except DBP, there were basically no significant risk in most of the studied water bodies. DBP showed apparent ecological risks in all of the studied water bodies, particularly in the middle Yellow River, the Xuanwu Lake, the Yuehu Lake, etc. Field monitoring data of the Liao River and the Taihu Lake showed that DBP had moderate risks in some of the sampling sites of both the watersheds, while BBP posed moderate risks only on a few sites of the Liao River.