In this study, toxicological data for zinc （Zn）, cadmium （Cd）, hexavalent chromium （Cr （VI））, benzene, and nitrobenzene were collected from various databases and publications, screened and then constructed into species sensitivity distribution （SSD） curves. Then water quality criteria （WQC） were derived for protection of the freshwater aquatic life in China against five representative pollutants. The values derived in this study were compared with those issued by the US Environmental Protection Agency and the Chinese national environmental standard for surface water to identify factors underlying the differences. The results showed that the SSD curves for the five pollutants differed significantly, with the examined aquatic species being gen- erally more sensitive to Zn, Cd, and Cr （VI） than benzene and nitrobenzene. The acute WQC were： 48.43 μg L-1 for Zn, 0.4218 μg L-1 for Cd, 45.79μg L-1 for Cr （VI）, 2651 μg L-1 for benzene, and 1426 μg L-1 for nitrobenzene. The chronic WQC were： 20.01μg L-1 for Zn, 0.2428 μg L-j for Cd, 14.22 μg L-1 for Cr （VI）, 530.2 μg L J for benzene, and 286.2 μg L-1 for nitroben- zene. The results of this comparative study of representative pollutants may offer guideline values for future WQC studies for China.
The concentrations of PAHs in the surface waters from seven river basins in China were summarized from literature published from 2000-2010. Subsequently, the risks from individual PAHs and Y. PAHs in the surface waters of China were quantified by comparing the overlap between the probability distributions of exposure concentrations with the probability distributions of toxicity data. The results show that the concentrations of 15 PAHs in the surface waters ranged from 3.09 to 38139.00 ng L-a, with a geometric mean of 474.93 ng L-1. The significantly higher concentrations of the 15 PAHs occurred in the surface waters from northern China when compared with those from southern China. The concentrations of the 15 PAHs in Chinese surface waters were higher than those in other waters worldwide. The MOSI0 （margin of safety） values were calculated at 90th percen- tile values of exposure concentrations and 10th percentile values of toxicity data, with 5.75, 0.17, 2.33, 0.30, 0.57, 1.74, 1.05, and 0.11 for Ace, Ant, Flu, BaP, Flua, Nap, Phe, and Pyr, respectively. The probabilities of the individual PAH concentrations exceeding the 10th percentile value of the toxicity data were 6.06%, 2.07%, 9.51%, and 2.07% for Nap, Ace, Phe, and Flu, re- spectively, suggesting minimal risk to aquatic organisms; however, the probabilities of BaP, Ant, Flua, and Pyr exceeding this value were 19.49%, 25.46%, 15.15%, and 30.50%, respectively, indicating potential risks. Among the individual PAHs, the ecological risk from Pyr was the highest, followed by, in descending order of risk, Ant, Bap, Flua, Phe, Nap, Flu, and Ace. Additionally, the combined ecological risk of ~ PAH8 in Chinese surface waters was significantly higher than any that of in- dividual PAHs alone. The MOS0 values in the river basins were 〈 1, except for the Haihe River Basin, suggesting a potential combined risk from E PAH8 in the other six fiver basins. The probabilities calculation indicate that low to high ecological risk from E PAH8 for all aquatic species was re
