Spatial Distribution of Dioxins and Furans in Surface Sediments in Dau Tieng Reservoir, Vietnam

Abstract

The composition and concentration of dioxins, furans, and agricultural chemicals in Dau Tieng reservoir sediments were determined to understand the horizontal distribution of PCDFs/Ds in 2020. The concentrations of agricultural chemicals in the reservoir sediment bed were negligible compared to the threshold (< 10 μg.kg-1, dry weight) and are not the source of PCDFs/Ds in the reservoir bed. This result proved that plant protection chemicals in the basin have been well controlled recently. PCDFs/Ds had negligible concentrations compared to the thresholds regulated by Vietnamese and international standards. The high concentrations of 1,2,3,4,6,7,8-HpCDD and OCDD were recorded at the site DT07, DT09, and DT12 with the order DT7 < DT9 < DT12. In addition, 2,3,4,6,7,8-HpCDF recorded at DT7 and DT9 with high concentrations is one of the most abundant congeners in cement factory wastewater. These results showed that PCDFs/Ds were mainly airborne from the North of the reservoir, where the cement factories could be the emission source, and spread toward the southwest. The PCDFs/Ds can also be transported between sampling sites in the reservoir bed due to differences in topographic elevation. The dioxin homologues distribution model in the sediments of Dau Tieng reservoir confirmed that the dioxins and furans in Dau Tieng reservoir sediments mainly come from atmospheric deposition.