Development of emergency water quality standard for Cr6+ and Hg2+ in Liao River basin

摘要

The acute toxicity data of Cr6 +and Hg2 +to the aquatic organisms in Liao River basin was collected and screened. Calculated results of criteria values using popular species sensitivity distribution（SSD） methods were evaluated through data analysis. The comprehensive methodology of emergency water quality standards（EWQSs） was established on the basis of the SSD method of Australia and New Zealand according to the evaluation results. The affected fractions of the aquatic organisms were set to be 5 %,15 %,30 % and 50 %,corresponding to the risk grades of Ⅰ,Ⅱ,Ⅲ and Ⅳ,and four-grade EWQSs,respectively. The EWQSs for Cr6 +and Hg2 +in the Liao River were derived and the corresponding risk indicators were also proposed. The results showed that the four-grade EWQSs 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 EWQSs 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 provided valuable information for the risk analysis of sudden ambient water environmental pollution accident.