Paper No. 6
Presentation Time: 2:50 PM
AMENDMENT WITH WATER TREATMENT RESIDUALS LOWER HUMAN HEALTH RISK FROM EXPOSURE TO ARSENICAL PESTICIDE-APPLIED SOILS
Arsenic has been used extensively in agriculture via pesticides, crop desiccants etc, which has left a legacy of arsenic-rich soils in a global scale. Widespread urban sprawl converting former agricultural lands into residential properties has increased the potential of human exposure to soil arsenic via a variety of pathways, including soil ingestion by hand-to-mouth activity in children. In-situ immobilization of arsenic in soils results in lowering arsenic bioavailability, hence, in reducing human health risk from chronic exposure. Drinking water treatment residuals (WTRs) promote in-situ immobilization of arsenic in soils in a way that is inexpensive and less disruptive to the natural landscape. WTRs are by-products of the drinking water purification process that typically contain - depending on the treatment process - sediments, organic matter, Al/Fe oxides and activated C. The metal oxides/hydroxides are typically amorphous and have high affinity for oxyanions due to both high specific surface and favorable pH dependent surface charge. Short- and long-term, laboratory and greenhouse studies were conducted to understand arsenic retention-release by Fe- and Al-based WTRs and WTR-amended soils. In-vitro and in-vivo arsenic bioavailability was evaluated using simulated human gastro-intestinal solutions and the nude mice model, respectively. Both aqueous and surface speciation of arsenic was studied. Results show that WTR amendment has the potential to develop into an effective green remediation technology for arsenic contaminated soils.