Author(s): Blute, N.K.; Jay, J.A.; Swartz, C.H.; Brabander, D.J.; Hemond, H.F.
In: Blute, N.K., J.A. Jay, C.H. Swartz, D.J. Brabander and H.F. Hemond (2009). Aqueous and solid phase arsenic speciation in the sediment of a contaminated wetland and riverbed. Applied Geochemistry, 24 (2): 346-358.
Type: Journal article
Link to SEI author(s):
Aqueous and solid phase arsenic speciation in the sediments of a contaminated wetland and riverbed
Testing included a sequential extraction method designed for and standard-tested with As phases and pE/pH equilibrium modeling. The uppermost sediments in the Wells G & H wetland contain elevated concentrations of both dissolved and solid phase As (up to 2,000 μg/L and 15,000 μg/g, respectively) and a maximum concentration between 30 and 40 cm depth.
Measurements obtained in this study suggested that As in the wetland sediments was predominantly adsorbed, likely onto amorphous Fe (hydr)oxide phases and mixed valence Fe phases. In the riverbed sediments, however, a relatively greater proportion of the solid As was associated with more reduced and crystalline phases, and adsorbed As was more likely associated with Al oxide or secondary reduced Fe phases.
pH–pe modeling of the Fe–As–S system was consistent with observations. The association of As with more oxidized phases in the wetland compared with the riverbed sediments may result from a combination of plant activities, including evapotranspiration-driven water table depression and/or root oxygenation.
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