Monday, November 13, 2006

Micro-Porosity Effects on Arsenic(V) Bioaccessibility in Soils.

Rupali Datta1, Konstantinos Makris1, Dibyendu Sarkar1, Peter I. Ravikovitch2, and Alexander V. Neimark2. (1) University of Texas at San Antonio, 6900 N. Loop 1604 West, San Antonio, TX 78249, (2) TRI/Princeton, 601 Prospect Ave, Princeton, NJ 08542

Ingestion of soil via "hand-to-mouth" activity by children is the #1 exposure pathway for arsenic (As) in pesticide-contaminated residential properties. Arsenic bioaccessibility in soils is of primary importance to developing appropriate risk assessment and soil remediation approaches. Current As bioaccessibility models rely partly on soil chemical properties and neglect the potential importance of soil physical properties such as porosity and specific surface area on potentially bioaccessible soil As. Ongoing work in our laboratory shows a significant relationship between specific surface area (N2 and CO2 gas adsorption data) and soil As bioaccessibility as measured using a traditional in-vitro stomach phase test. The obvious relationship between specific surface area and porosity led us to hypothesize that soil pore volume and pore size distribution exerts a significant effect on the overall magnitude of soil As bioaccessibility. Total and differential (with respect to pore diameter) meso- and micro-pore volume distributions of the soils are being related to soil As bioaccessibility data collected for 17 soils with unique and vastly different physicochemical properties.