HR: 0800h
AN: H21C-1037    [Abstracts]
TI: Evaluation of a Chemical Fixation Technique for Remediation of Soils Contaminated with Arsenic Trioxide
AU: * Donahoe, R J
EM: rdonahoe@wgs.geo.ua.edu
AF: The University of Alabama, Department of Geological Sciences, Tuscaloosa, AL 35487-0338 United States
AU: Yang, L
EM: yang003@bama.ua.edu
AF: The University of Alabama, Department of Geological Sciences, Tuscaloosa, AL 35487-0338 United States
AU: Graham, E Y
EM: bgraham@wgs.geo.ua.edu
AF: The University of Alabama, Department of Geological Sciences, Tuscaloosa, AL 35487-0338 United States
AU: Redwine, J C
AF: Southern Company Services, Inc., Inverness Center Parkway, Birmingham, AL 35242 United States
AB: The results of an experimental study designed to test a chemical fixation technique for remediation of arsenic-contaminated soils are reported. Soil samples were collected from two industrial sites where herbicide application contaminated the soil with arsenic trioxide. Weathering has redistributed and changed the speciation of the arsenic and caused contamination of soil water and groundwater. Remediation techniques requiring excavation of the affected soil are impractical due to the lack of site access for heavy equipment and the large area impacted. To address these concerns, an in situ treatment method was developed and tested in laboratory experiments. Column experiments were conducted to evaluate the effectiveness of the soil treatment method. Homogenized soil samples from each site were packed into duplicate 4"x18" Plexiglas columns and treated with ferrous sulfate solution using a flow rate of 2 ml/min until iron breakthrough was achieved. Another pair of packed columns was leached with DDI water to provide baseline data for the effect of the treatment solution matrix on arsenic mobility. All soil column effluents showed an initial spike of arsenic after onset of fluid flow; however, the soils undergoing treatment leached less than one half the amount of arsenic leached from the soil by DDI water. When the soil became saturated with the ferrous sulfate treatment solution, effluent solution arsenic concentrations fell below detectable levels. After breakthrough of the treatment solution was achieved, the treated soil columns were allowed to drain and cure for 7 days. One treated soil column and one untreated soil column were then continuously leached with EPA Method 1312 SPLP fluid to observe the effect of treatment on the mobility of arsenic. The second set of treated and untreated soil columns was also leached with SPLP fluid, but in a manner designed to simulate periodic rainfall events. Preliminary experimental results show that ferrous sulfate treatment dramatically decreases the amount of leachable arsenic, compared to untreated soil. After 30 hours of SPLP leaching, there was no detectable arsenic in the effluent of the treated soil column. In contrast, more than 5 mg/L arsenic was mobilized from the untreated soil in the same time period. These results indicate that in situ chemical fixation of arsenic-contaminated soils is an effective and low-cost treatment method for sites at which the use of heavy equipment is not feasible.
DE: 1045 Low-temperature geochemistry
DE: 1065 Trace elements (3670)
DE: 0345 Pollution--urban and regional (0305)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting