Geochemical and hydrologic controls on the mobilization of arsenic derived from herbicide application

GEOC 123

Arthur G. Fitzmaurice, agfitz@caltech.edu1, A. Azra Bilgin1, Janet G. Hering, jhering@caltech.edu1, Peggy A. O'Day2, David R. Burris, istpanamacity@aol.com3, and H. James Reisinger3. (1) Environmental Science and Engineering, California Institute of Technology, 1200 E. California Boulevard, MC 138-78, Pasadena, CA 91125, (2) School of Natural Sciences, University of California, Merced, CA 95344, (3) Integrated Science and Technology, Inc, 228 Harrison Avenue, Suite 102, Panama City, FL 32401
The mobilization of arsenic and its persistence in soil were examined at an electrical sub-station at Tyndall Air Force Base (FL), where inorganic arsenical herbicides were applied until the mid-1970s. Soil in the source area remains contaminated with up to 280 mg/kg total arsenic; the maximum arsenic concentration in the groundwater plume is 1.2 mg/L. Source area soil was exposed to background groundwater in batch and static column leaching experiments, which demonstrated that arsenic in the contaminated soil is geochemically labile. The dependence of the concentration of arsenic leached from the soil on the solids concentration is consistent with sorption as the mechanism for arsenic association with the soil. This interpretation is supported by X-ray absorption spectroscopy data. These results suggest that the persistence of arsenic in the source area soils for more than thirty years is due to limited flushing of the source area by precipitation (i.e., hydrologic control).
 

Physical Chemistry of Soil and Aquifer Systems: A Symposium in Honor of Garrison Sposito
1:30 PM-4:40 PM, Wednesday, 13 September 2006 Moscone Center -- Room 256, Oral

Division of Geochemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006