Arsenic mobilization in sediments: An investigation using in situ sampling techniques
We have recently developed Diffusive Gradients in Thin films (DGT) and Diffusive Equilibrium in Thin films (DET) techniques that permit the measurement of high-resolution porewater distributions of As(III), total inorganic arsenic and Fe(II). These novel techniques were utilized to investigate the mobilization of arsenic in sediment mesocosms during oxic and anoxic conditions. Codistributions of As(III) and Fe(II) during induced anoxia revealed tightly coupled mobilization of both species from the sediment to the porewater and into the overlying water, due to the reductive dissolution of Fe(III) (hydr)oxide minerals. Comparison of porewater distributions of As(III) and total inorganic arsenic measured by DGT indicated that As(III) was the primary species mobilized during anoxia. This approach to the investigation of arsenic mobilization in sediments provides highly representative data on a finer spatial scale than conventional sampling techniques.