HR: 0800h
AN: H21E-1388 [Abstracts]
TI: Leaching Behaviors of Five Arsenic-Contaminated Soils
AU: * Qi, Y
H21E-1388
AF: Department of Geological Sciences, University of Alabama, 202 Bevill Building, Tuscaloosa, AL
35487-0338
United States
AU: Donahoe, R J
H21E-1388
AF: Department of Geological Sciences, University of Alabama, 202 Bevill Building, Tuscaloosa, AL
35487-0338
United States
AU: Graham, E Y
H21E-1388
AF: Department of Geological Sciences, University of Alabama, 202 Bevill Building, Tuscaloosa, AL
35487-0338
United States
AB:
The vadose zone is susceptible to anthropogenic arsenic contamination and may serve as a long-term source of arsenic to
ground water. Understanding the processes governing the distribution of arsenic between the aqueous phase and the solid phase
is crucial to minimizing the environmental impact of vadose zone contamination. Arsenic can be retained by several soil
components through adsorption. The magnitude and controlling factors of arsenic adsorption by these individual components
have been investigated by a number of researchers. The desorption behavior of arsenic in bulk soil from actual contaminated
sites, however, is rarely reported.
Soil samples were collected from five sites contaminated with herbicide containing arsenic trioxide. The environmentally
available element concentrations of each soil were determined by microwave-assisted acid digestion (MWD) and ICP-AES
analysis. A ferrous sulfate solution was applied to the contaminated soil to precipitate ferric hydroxide as an arsenic
fixation method. Sequential leaching experiments were performed upon the treated and untreated soil samples to evaluate the
effectiveness of the treatment method. Supernatant leachate solutions were analyzed for total arsenic by ICP-AES.
MWD results showed that the original soils contain 47 to 316 ppm arsenic, on a dry weight basis. The arsenic concentrations
in the initial leachate ranged from 0.42 to 1.37 ppm for the untreated soils. Due to the high Kd values of the rainwater
leachable portion of the soil arsenic, 500 to 4000 pore volumes of SPLP solution were required to bring the leachate arsenic
concentration below the MCL for arsenic (50 ppb). In contrast, the ferrous sulfate treatment successfully transferred the
loosely adsorbed portion of the soil arsenic to strongly bonded adsorption sites on ferric hydroxide. After treatment, the
two soil samples with low calcium content lost their pH buffer capacity and their leachate maintained a pH value of 4.5. No
arsenic was detected in the leachate of these two treated samples during three months of sequential leaching. For the other
three soils with higher buffer capacity, the treated samples also showed significant decrease in both initial (56-86%
decrease) and overall (43-62% decrease) release of arsenic.
DE: 1030 Geochemical cycles (0330)
DE: 1065 Major and trace element geochemistry
DE: 1831 Groundwater quality
DE: 1865 Soils (0486)
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: Fall Meeting 2005