HR: 13:55h
AN: H13L-02    [Abstracts]
TI: Subsurface Occurrence, Distribution, and Speciation of Arsenic in the Southern High Plains
AU: * Venkataraman, K
EM: kartik.venkataraman@ttu.edu
AF: Rainwater, K
EM: ken.rainwater@ttu.edu
AF: High concentrations of arsenic have been found in the groundwater of the Southern High Plains of Texas. While the arsenic may be naturally occurring, the effects of land use patterns cannot be ignored. To determine the potential source(s) of arsenic, a study involving collection of water samples from public supply wells and soil samples from monitoring wells installed by The Texas Tech University Water Resources Center was undertaken. Groundwater samples were collected from 54 public water wells spread over 18 counties and from 8 monitoring wells spread over 3 counties. Soil samples from different profiles of the vadose zone of the same three monitoring wells were extracted for arsenic. Speciation of arsenic was quantified in order to help better understand the subsurface geochemical interactions. Total arsenic levels ranging from non-detect (<1 ėg/L) to 38 ėg/L were observed in the groundwater. Over 90% of the wells had significantly higher concentrations of As(III) than As(V). Several public water supply wells were found to have total arsenic levels in excess of 10 ėg/L, the new MCL that came into effect last year. The range of concentration of total arsenic in the soil samples was from non-detect to 0.42 mg/kg (dry weight). Positive correlation between depth and total arsenic were observed, with As(III) being significantly higher than As(V) with increasing depth. Correlations between arsenic species and related cations and anions such as iron, copper, manganese and sulfate are being studied. Modeling tools such as MINTEQ are being used to compare predicted speciation ratios with those observed in the samples collected in the field to better understand subsurface geochemical interactions.
DE: 1806 Chemistry of fresh water
DE: 1831 Groundwater quality
DE: 1884 Water supply
SC: Hydrology [H]
MN: 2007 Fall Meeting