Selection of Priority Contaminants in a Watershed Using Risk Ranking Methodology

Abstract

The present study focuses on the risk rankings of different contaminants from Daling River in Liaoning Province, China, for categorizing the environmental risk levels in the river. Eighteen surface water samples were collected from Daling River, which has been polluted by the surrounding fluorine industries for years. Perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and heavy metals were analyzed, and relevant eco-toxicity data obtained from literatures were considered. The median concentrations of PFOS and PFOA were observed as 0.77-3.57 ng·L-1 and 82.93-344 ng·L-1, respectively, which were lower than the standard limits of the United Kingdom. The concentrations of heavy metals and organochlorine pesticides (OCPs) were found to be lower than level Ⅳ of the Chinese national environmental quality standards for surface water. The maximum concentrations of mercury (Hg) and arsenic (As) were higher than the standard level Ⅲ. The environmental risks ranged from 1.42×10-6 to 2.3×10-2. The order of the risks by potential environmental contaminants was Cu > Zn > As > p,p'-DDE > p,p'-DDT > Cd > Pb > Hg > PFOA > γ-HCH > Cr > Ni > α-HCH > PFOS. The present findings revealed that the environmental risks of PFOS and PFOA were relatively low and these were not taken as priority contaminants, but the accumulation risks could not be overlooked for a long time. Among the contaminants, copper (Cu) was the priority contaminant of Daling River. Hence, necessary measures are recommended to reduce the potential effects of contaminants on the environment.