Assessing remobilization characteristics of arsenic (As) in tributary sediment cores in the largest reservoir, China

- DGT was used to assess the remobilization characteristics of As in a tributary sediment of the TGR.
- The horizontal and vertical distributions of CDGT-As varied in this study.
- As had the diffusion potential from the deep sediment to the surface sediment and overlying water.
- The remobilization of As may be associated with Fe and Mn.
- Sulphide was remobilized simultaneously with As in the tributary sediments.

The environmental impact of the Three Gorges Reservoir (TGR) in China has raised widespread concern especially in relation to metal pollution. The diffusive gradient in thin films (DGT) technology was applied to investigate arsenic (As) remobilization in sediment cores collected from the main stream and a tributary in the TGR during July 2015. The results showed that the horizontal and vertical distributions of CDGT-As varied among the four sampling sites. For the same DGT probe, the horizontal distributions of CDGT-As (0-6 mm, 6-12 mm, 12-18 mm) exhibited similarity in the overlying water and different tendencies in the sediment profiles; the vertical variations of CDGT-As showed different mobilization tendencies. Moreover, the mobility patterns of As in the sediment profile showed the diffusion potential of As from the deep sediment to the surface sediment and overlying water were in the order of MX-2< MX-1< CJ < MX-3. In addition, similar distribution characteristics and correlation analysis showed that the mechanisms of As mobility were associated with Fe and Mn. The results also showed that sulphide and As were simultaneous remobilization in the tributary sediment core in the TGR.