Poster Number 33
Complex geochemical and biological mechanisms control the distribution of arsenic within repositories in the biosphere, hydrosphere, and lithosphere. Arsenic in water is primarily found in two oxidation states, As (III) and As (V). As (III) is considered more toxic than As (V), and is generally less mobile. Controls on the distribution of arsenic include: redox conditions, pH, presence of Iron and Manganese Oxyhydroxides, and metabolic activities of microorganisms.
Chemical availability of As is an indirect measure of bioavailability. It is assumed that dissolved phases are most bioavailable. Chemical availability of As is dependent on speciation. Therefore, when the speciation of arsenic in a soil system is known the chemical availability becomes a good indicator of bioavailability.
In this study we use DOWEX M4195, Fe3+ substituted, chelating resin as an in-situ sink to measure arsenic chemical availability in natural soils in Taiwan and Texas. The resin will adsorb aqueous arsenate and arsenite acting as an artificial cell membrane. By using the resin as an in-situ sink we will be able to characterize arsenic speciation across a soils transect of varying pH with minimal perturbations to the system. Allowing the resin to remain in the soils will yield time-integrated As chemical availabilities.
The chemical availability of arsenic in the soil waters will be recorded as total arsenic adsorbed to the resin. The goal of this project is to better understand arsenic availability via oxidation state in a natural soils environment. The DOWEX M4195, Fe3+ substituted, chelating resin method will be an effective measure for understanding arsenic contamination risks.