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Mercury contamination in the Red river watershed: a review of the contaminated sites

This study is based on two sampling campaigns covering the whole Vietnamese Red River watershed in 40 sites at low and high water levels during 2009 in order to determine the seasonal and spatial variations of Hg concentrations in stream sediments. The results showed that the Hg concentrations during low water level were clearly higher than that during high water level, demonstrating an effect of particle (grain) size (i.e. significant contribution of less mercury-contaminated particles in high water level). | Vietnam Journal of Earth Sciences 36 (2014) 497-503 Vietnam Academy of Science and Technology Vietnam Journal of Earth Sciences (VAST) Website: http://www.vjs.ac.vn/index.php/jse Mercury contamination in the Red river watershed: a review of the contaminated sites Dang Thi Ha*1, Alexandra Coynel2, Marine Deschatre2 1 Institute of Chemistry, VAST-Hanoi, Vietnam 2 University of Bordeaux 1, UMR CNRS 5805 EPOC, France Accepted 27 December 2014 ABSTRACT This study is based on two sampling campaigns covering the whole Vietnamese Red River watershed in 40 sites at low and high water levels during 2009 in order to determine the seasonal and spatial variations of Hg concentrations in stream sediments. The results showed that the Hg concentrations during low water level were clearly higher than that during high water level, demonstrating an effect of particle (grain) size (i.e. significant contribution of less mercury-contaminated particles in high water level). In addition, in order to assess spatial distribution of the Hg contamination in the Red River watershed and localize geochemical anomalies, multidimensional statistical analyses combined with Hg maps generated by GIS tool were used. We observed that the high mercury anomalies are originated from the important pollutant sources (mining/smelting) located in the upstream and mid- Red River watershed, demonstrating an impact of anthropogenic activities on river Hg concentrations. Finally, the comparison between the Hg concentrations in the stream sediment from the Red River watershed and the consensus-based freshwater sediment quality guidelines (SQGs) indicated that the sediment quality for important areas of the Red River watershed is rather poor and probably represents serious threats to aquatic life. Keywords: Red River, Hg contamination,anomaly,sediment quality,GIS. © 2014 Vietnam Academy of Science and Technology 1. Introduction Mercury is known as one of the environmental pollutants, enhancing its toxicity