The mobility and transformation of arsenic （As） in salt marsh sediments were investigated in Dongtan wetland of the Yangtze River estuary, China. As in surface water, pore water and the rhizosphere sediments were qu...The mobility and transformation of arsenic （As） in salt marsh sediments were investigated in Dongtan wetland of the Yangtze River estuary, China. As in surface water, pore water and the rhizosphere sediments were quantified. The microcosm incubation experiments were conducted during the flooding of the sediments to examine As dynamics that occurred during changing redox conditions. The concentrations of dissolved As in pore water （0.04--0.95 ixmol/L） were significantly greater than that in surface water （0.03-0.06 lunol/L）. Under anoxic conditions, the reactive As could be initially mobilized by the reductive dissolution of Fe（III） （hydr）oxides. Subsequently, most of the dissolved As was likely to be associated with secondary iron （hydr）oxide phases and remained in solid phases. The seasonal variability of acid volatile sulfide concentrations suggest the anoxic conditions are enhanced during summer by Spartina alterniflora compared to Phragmites australis and Scirpus mariqueter, causing a notable increase in As mobility. Generally, there was a typical variation in redox conditions with season in salt marsh sediments of Dongtan wetland, in which the dynamics of As mobility and transformation possibly were controlled by iron, and all of this could be significantly influenced by the rapid spread of S. alterniflora.展开更多
基金supported by the funds of the National Program on Key Basic Research Project of China (No.2012CB957800)the Shanghai Commission for Science and Technology (No. 10DZ0581600)the Major Science and Technology Program for Water Pollution Control and Treatment (No. 2009ZX07317-006-01)
文摘The mobility and transformation of arsenic （As） in salt marsh sediments were investigated in Dongtan wetland of the Yangtze River estuary, China. As in surface water, pore water and the rhizosphere sediments were quantified. The microcosm incubation experiments were conducted during the flooding of the sediments to examine As dynamics that occurred during changing redox conditions. The concentrations of dissolved As in pore water （0.04--0.95 ixmol/L） were significantly greater than that in surface water （0.03-0.06 lunol/L）. Under anoxic conditions, the reactive As could be initially mobilized by the reductive dissolution of Fe（III） （hydr）oxides. Subsequently, most of the dissolved As was likely to be associated with secondary iron （hydr）oxide phases and remained in solid phases. The seasonal variability of acid volatile sulfide concentrations suggest the anoxic conditions are enhanced during summer by Spartina alterniflora compared to Phragmites australis and Scirpus mariqueter, causing a notable increase in As mobility. Generally, there was a typical variation in redox conditions with season in salt marsh sediments of Dongtan wetland, in which the dynamics of As mobility and transformation possibly were controlled by iron, and all of this could be significantly influenced by the rapid spread of S. alterniflora.
