(21c) Using Nitrogen and Carbon Dioxide Adsorption to Estimate Arsenic(V) Bioaccessibility in Soils

We propose a novel As(V) bioaccessibility model, which was tested on 17 model soils. The model includes only two parameters characterizing surface properties of soils that are readily determined from N2 and CO2-based specific surface areas( SSAs), and total organic carbon (OC) content. We found that N2 and CO2 molecules act as As(V) "surrogates", probing easily-accessible, and relatively difficult to access soil porosity, respectively. The objectives of this study were: i) develop and independently validate an As(V) sorption and bioaccessibility empirical model, utilizing soils comprising a wide range in texture, specific surface area and OC contents; and ii) relate the proposed soil physical properties to soil As bioaccessibility measured by an in-vitro stomach phase test. Three interrelated linear models were constructed that were significant (p<0.001) in explaining 50 and 95 % of the variability observed in As(V) sorption and bioaccessibility, respectively. The models successfully predicted bioaccessible As concentrations for 4 out of the five soils, reaching RMSE values of < 10 %. The performance of the proposed simple models is quite remarkable, which suggests that similar models may be effective for estimation of metals bioaccessibility in soils and sediments.