Selection of priority management of rivers by assessing heavy metal pollution and ecological risk of surface sediments.

This study aimed to select rivers of priority management through the assessment of heavy metal pollution of sediments. We investigated the distribution characteristics of heavy metals in surface sediments of the Nakdong River in South Korea and used various pollution indices to assess pollution risk and identify factors influencing pollution. The kriging method was used to determine heavy metal distribution. The pollution load index, potential ecological risk index, mean PEL quotient, and the Canada Council of Ministers of the Environment sediment quality index were used as sediment pollution assessment methods. The toxicity evaluation was performed on sites that appeared to be contaminated, by applying existing methods for assessing sediment pollution level and the national standards for evaluating the pollution level. The toxicity test was performed on Hyalella azteca, and a methodology for assessing sediment pollution level was proposed. Ecotoxicity was assessed at seven sites that were found to have heavy metal contaminants. The results showed that sites N1, N8, T28, and T29 were not toxic, while T8, T19, and T21 were. Thus, this study shows that high heavy metal pollution does not necessarily lead to a toxic environment. To assess sediment pollution, an additional assessment of toxicity should be made, along with assessments of existing sediment pollution. Our results demonstrate that streams showing high sediment pollution levels should be granted priority in management. The efforts should particularly focus on Cu at T8, Cr at T19, and Hg at T21.