针对辽河流域的特征污染物六价铬和无机汞，广泛搜集、筛选了水生生物的急性毒性数据，对国际物种敏感度分布（SSD）主流方法的基准计算结果进行了评价。基于评价结果，以澳大利亚和新西兰的SSD技术为基础，初步建立了综合的应急水质标准方法学。将受污染物暴露胁迫的水生生物比例达到5 %、15 %、30 %和50 %时对应的生态风险级别分别设定为I级、II级、III级和IV级，且对应于4级应急水质标准。推算了六价铬和无机汞的辽河流域应急水质标准限值，提出了相应的流域风险指示生物。结果表明，六价铬的4级应急水质标准分别为2.85 μg/L、21.0 μg/L、161 μg/L和797 μg/L，风险指示生物为溞类（II级）、青虾（III级）和鳙鱼或蝌蚪（IV级）；无机汞的4级应急水质标准分别为0.59 μg/L、2.32 μg/L、6.25 μg/L和15.6 μg/L，风险指示生物为鲫鱼或溞类（II级）、青虾（III级）、水丝蚓或蟹类（IV级），为突发性水环境污染事故风险分析提供了参考。

The acute toxicity data of Cr6+ and Hg2+ to the aquatic organisms in Liaohe River basin was collected and screened. Calculated results of criteria values of international species sensitivity distribution (SSD) methods were evaluated through data analysis. The comprehensive methodologies of emergency water quality standard (WQS) were established based on the SSD method of Australia and New Zealand according to the evaluation results. The affected fractions of the aquatic organisms was set to be 5 %, 15 %, 30 % and 50 %, corresponding to the risk grades of I, II, III and IV, and four-grade emergency WQS, respectively. The emergency WQS for Cr6+ and Hg2+ in the Liao River basin were derived and the corresponding risk indicators were also proposed. The results showed that the four-grade emergency WQSs for Cr6+ were 2.85 μg/L, 21.0 μg/L, 161 μg/L and 797 μg/L, respectively, and the risk indicators were daphnia (grade II), shrimp (grade III), and the bighead fish or tadpole (grade IV). The four-grade emergency WQSs for Hg2+ were 0.59 μg/L, 2.32 μg/L, 6.25 μg/L and 15.6 μg/L, respectively, and the risk indicators were crucian carp or daphnia (grade II), shrimp (grade III), and worm or crab (grade IV). The results provide valuable information for the risk analysis of emergency ambient water environmental pollution accident.