Redox-controlled groundwater mobilization of soil arsenic: A case study and model
Conference
·
OSTI ID:416846
Arsenic contaminates the groundwater beneath and downstream from a chemical manufacturing plant, although historical waste emissions from the plant have consisted principly of isopropanol, and fatty acids. Groundwater and soil analysis of organics, metals, anions, D.O. (dissolved oxygen), and redox potential are consistent with a model for redox-controlled mobilization of that arsenic which is naturally present in the soil at background concentrations of around 10 mg/kg. According to this model, aerobic biodegradation of organic compounds from the plant`s waste stream consumes D.O. and lowers the redox potential of portions of the aquifer. Somewhere below 0.5 mg/l D.O., particles of iron and manganese hydroxide tend to dissolve and release the arsenic adsorbed to their surfaces. Bacterial mediation and organic complexation are then believed to determine the formation of soluble arsenite and arsenate complexes. A numerical flow/transport/reaction model of the plant site was set up using the BIOPLUME II code in order to simulate bacterial D.O. consumption in the aquifer and evaluate remedial alternatives. Modeling results show that site cleanup (increase of D.O. above 0.5 mg/l) will require approximately nine years with no action, four years with excavation of the source leachfield, and two years with source excavation plus oxygen injection. A combination of soil excavation and oxygen injection is presently under design in order to quickly reduce the consumption of D.O. in the saturated aquifer and remove a necessary condition for arsenic mobilization.
- OSTI ID:
- 416846
- Report Number(s):
- CONF-951023--
- Country of Publication:
- United States
- Language:
- English
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