Aquatic ecological risk assessment of OCPs in Huaihe River, Jiangsu section

The Huaihe River Basin, located between the Yellow River and the Yangtze River, is one of the most populated areas in the eastern part of China. The Huaihe River is probably the most heavily polluted one among the three largest rivers in China. The Jiangsu section is the downstream reaches of the Huaihe River, where organochlorine pesticides （OCPs） may come from local discharge due to flourishing industry and agriculture, and also from inflows from upstream. OCPs are usually hazardous organic pollutants, and may endanger the aquatic ecosystem of the Huaihe River, Jiangsu section. Surface water of the Huaihe River, Jiangsu section in both high-flow period and low-flow period was sampled and OCPs were determined using GC-ECD. 15 OCPs were detected, including 2,4＇-DDT, 4,4＇-DDT, 4,4＇-DDD, α-HCH, β-HCH, γ-HCH, aldrin, endrin, dieldrin, methoxychlor, heptachlor, hexachlorobenzene（HCB）, α-endosulfan, α-Endosulfan and heptachlorepoxide. The span of total OCPs concentration is between 26.27-124.39 ng/L. Among the 15 OCPs detected, aquatic ecological risk assessment was performed for 12 ones except for α-endosulfan, α-endosulfan and heptachlorepoxide due to lack of the relevant toxicity data of the three compounds. The acute toxicities of 12 OCPs to multi aquatic species were collected from AQUIRE database and other sources. Environmental Concentration Distribution （ECD） and Species Sensitivity Distribution （SSD） were achieved after Kolmogorov-Smirnov test. The risk quotient distributions were acquired using Monte Carlo simulation. The aquatic ecological risks caused by single OCPs were analyzed. It is shown that endrin and 2,4＇-DDT have the highest risk while HCB and HCHs have the lowest risk. Then the joint ecological risk caused by all 12 OCPs was calculated based on the concept of equivalent concentration and it proves to be significantly higher than risk caused by any single OCP. Furthermore, the probability of aquatic ecological risk was calculated according to different ecological risk criteria （ERC）. The comparative analysis shows that ERC is very important to the result of ecological risk assessment.

Aquatic ecological risk assessment of OCPs in Huaihe River, Jiangsu section