In this study, we consider ability of self-purification for a rational water quality management. And we assess the risk of
Alkyl Benzene Sulfonic acid sodium salt(ABS) of harmful ingredients in Anseong Cheon watershed using QUAL2E model.
The observations and simulated results were fitted well for BOD and ABS, but even though the trend of DO concentration
change was well represented, the error between observation and simulation values was existed. We assessed the Risk
assessment by calculating Risk quotient(RQ) by Predicted Exposure Concentration(PEC) and Predicted No-Effect
Concentration(PNEC). Results of the impact of ABS on the self-purification of the river were Anseongcheon[0.0003(Bressan),
0.06(Criteria of Ministry of environment)], Jinwicheon[0.0002(Bressan), 0.04(Criteria of Ministry of environment). And result
of the impact of ABS on the Aquatic ecosystem of the river were Anseongcheon[0.0667(Bressan), 0.005(Criteria of Ministry
of environment)], Jinwicheon[0.1(Bressan), 0.0075(Criteria of Ministry of environment). All of these results were smaller than
the 1.0 which is the reference value suggested by Norification No.30 of the National Institute of Environment Research. So,
ABS did not affect a self-purification and aquatic ecosystem of the river. The method suggested in the study is a simple
one and can provide more information for harmful ingredients than criteria of Ministry of environment.