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Surface Sediment Quality of the Red River (Vietnam): Impacted by Anthropogenic and Natural Factors
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International audience. Riverine surface sediments are known to be important sources and sinks for different variables like metals, organic carbon and nutrients. This paper presents the surface sediment quality of the Red River which was monitored for nine trace metal elements, total organic carbon and nutrients (nitrogen, phosphorus and silica) during four sampling campaigns in 2019. The results showed that Fe and As concentrations were higher than the allowed values of the Vietnam National technical regulation on the surface sediment quality QCVN 43:2017/BTNMT. Trace metal element concentrations were, from highest to lowest, Fe > Mn > Cu > Zn > Pb > Cr > As > Cd > Hg. The geoaccumulation index and the enrichment factor values revealed that the Red River sediments were polluted by As; moderately polluted by Cu, Pb, Cd, and Hg; and uncontaminated by other metals (Mn, Cr and Zn). For other variables, total organic carbon (0.43 +/- 0.31%), total nitrogen (0.09 +/- 0.04%), and total phosphorus (0.060 +/- 0.018%) were low in comparison with other urban rivers, whereas total silica (29.93 +/- 4.52%) seemed to be high. Spatially, the lowest values of most variables were observed at the Hoa Binh site, where human population and activities are lowest and when discharge was highest. In contrast, most variables were highest at the Ba Lat site where the human activities clearly impacted on the Red River. These results indicate that the Red River sediment is affected by a combination of natural characteristics and human activities in the basin.
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