Characteristics of cadmium remobilization in tributary sediments in Three Gorges Reservoir using chemical sequential extraction and DGT technology. (November 2016)

• Record Type: Journal Article
• Authors: Xu, Dongyu; Gao, Bo; Gao, Li; Zhou, Huaidong; Zhao, Xingjuan; Yin, Shuhua
• Is Part Of: Environmental pollution. Volume 218(2016)
• Page Start: 1094
• Page End: 1101
• Publication Date: 2016-11
• Subjects: Three Gorges Reservoir (TGR) -- Cadmium -- Diffusive gradients in thin films (DGT) -- BCR sequential extraction -- Sediment-water interface; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2016.08.062
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: The Three Gorges Reservoir (TGR) is the largest reservoir in China. Cadmium (Cd) is a primary pollutant in the TGR, and its speciation and bioavailability have attracted extensive attention since TGR submergence. In this study, Chelex-100 DGT (diffusive gradient in thin films) and the sequential extraction method were used to investigate the bioavailable Cd in sediments obtained from a typical tributary (Meixi) and mainstream (Yangtze) in the TGR. The total Cd concentrations in sediments of the four stations were also determined. In comparison to the concentrations of labile Cd measured by DGT (CDGT -Cd) in four profiles, CJ and MX-upstream/downstream were at potential risk for Cd release from surface sediments using the apparent diffusion flux across the interface numerical model. The order of CDGT -Cd in surface sediments was as follows: CJ > MX-downstream > MX-upstream > MX-midstream. Additionally, a positive correlation was demonstrated between CDGT -Cd and Cd in the exchangeable fraction (F1) in the surface sediments, indicating that Cd in the exchangeable fraction was readily captured by DGT. A negative correlation was observed between CDGT -Cd and CDGT -Fe, CDGT -Mn in the sediment-water-interface (SWI), suggesting that Fe/Mn oxides did not control the release of labile-Cd from sediments. Furthermore, a positive correlation existed between the CDGT -Cd in the surface sediments and Cd in the oxidizable fraction (F3), illustrating that Cd sorbed or bound with organic matter or sulfide was labile and released into the water phase from the surface sediments. A dark area was found in the AgI gel, which further demonstrated that Cd simultaneously was released with sulfide in this area. Highlights: DGT-labile Cd was used to assess sediment coresina typical tributary and mainstream in the TGR. Fe/Mn oxides did not control the release of labile Cd in sediments. Organic matter and sulfides governed the mobility of labile Cd in surface sediments. A dark area was found in AgI gel indirectly demonstrated Cd combining with sulfide to release. Labile Cd in the sediments has the potential to release into the overlying water. Abstract : DGT-labile Cd was positively correlated with Cd in exchangeable and oxidizable fraction in the TGR tributary sediments.