| Water quality criteria are the foundation of determination of water quality standard, and they are of importance in environmental management. Because the current water quality standard in China is established on foreign water quality criteria, it is hard to provide suitable protection to the aquatic system and human health in China. Take hexavalent chromium as examples, the present study developed freshwater aquatic life criteria in China primarily based on the SSD method of the U.S. Environmetal Protection Agency. The tiered system of nation and basin was used in the study of hexavalent chromium criteria, while criteria were studied primarily on the national scale. The study is helpful to determine relative water quality standard in China. The detail results and main conclusions was summarized as follows:1. The status and health risks of eight metals, Pb, Cd, Cr, Cu, Zn, Fe, Ni and Mn, in surface water from Taihu Lake and Liao River Basin were evaluated. The results showed that the maximum hazard quotients (HQ) value through ingestion pathway and dermal adsorption pathway was 2.74E-01 (Ni) and 2.57E-02 (Cd), respectively. However, the individual hazard quotient and total hazard index of eight metals through ingestion and dermal adsorption pathway was all lower than 1, indicating that the pollution situation in the surface water of Taihu Lake concerning these metals has no or low adverse health effects.2. A survey on the extent and distribution of heavy metals (Cd, Cr, Pb, Ni, Cu, Zn) in surface sediments of Taihu Lake and Liao River basin was conducted, and then the environmental impact of these pollutants was assessed by using the Hakanson potential ecological risk index based on the obtained results.Following the classification, the Er1 values of the selected metals (except Cd) were less than 40 in all the sampling sites, suggesting that the potential ecological risk of these metals were low. The values of Eri for Cd were>40 in most of these sites, indicating that Cd had a moderate risk. On the other hand, the mean value of RI was 85.10 and 45.95 for all the the sampling sites of Taihu Lake and Liao River basin, respectively. Therefore, that heavy metal in sediments of Taihu Lake and Liao River basin has a low potential ecological risk.3. In order to accurately evaluate the toxicity of pollutants on indigenous aquatic organisms, and provide data for scientifically deriving the water quality criteria protecting aquatic organisms in China, Cr(VI), ammonia, nitrobenzene,2,4,6-trichlorophenol and Chlorpyrifos, were selected to study those acute toxic effects on China indigenous aquatic organisms (Pelteobagrus fulvidrac, Hypophthalmichthy smolitrix, and Carassius auratus(Linnaeus)). The result of acute toxicity test showed:96h-LC50 of Cr(VI) on Pelteobagrus fulvidrac, Hypophthalmichthy smolitrix and Carassius auratus(Linnaeus) were 15.79 mg/L,168.5 mg/L and 13.16 mg/L, respectively; 96h-LC5o of ammonia on Pelteobagrus fulvidrac and Hypophthalmichthy smolitri were 16.63 mg/L and 16.86 mg/L, respectively; 96h-LC50 of Nitrobenzene on Pelteobagrus fulvidrac and Carassius auratus(Linnaeus) were 81.57 mg/L and 121.1 mg/L, respectively; 96h-LC50 of 2,4,6-trichlorophenol on Pelteobagrus fulvidrac and Carassius auratus(Linnaeus) were 81.57 mg/L and 121.1 mg/L respectively, respectively.96h-LC50 of Chlorpyrifos on Pelteobagrus fulvidrac and Carassius auratus(Linnaeus) were 0.182 mg/L and 0.282 mg/L, respectively.4. The results of study on hexavalent chromium criteria showed that the acute and chronic criteria for hexavalent chromium in China were 17.18μg/L and 7.59μg/L, respectively and they were closed to the U.S. national hexavalent chromium criteria. The acute criteria for Tai Lake and Liao River basin were 20.42μg/Land 16.34μg/L, respectively, while the chronic criteria for these basins were 5.44μg/L and 4.45μg/L, respectively. Because of scarcity of chronic toxicity data, the chronic basin criteria had more uncertainty than the acute basin criteria. The study on hexavalent chromium criteria is valuable to the foundation of tiered system of water quality criteria and standard in China.
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