The purpose of this study is to determine the distribution of arsenic in Texas groundwater;
assess the potential of past application of arsenical pesticides as a source of arsenic in groundwater in the
Southern High Plains and Southern Gulf Coast, evaluate the role of phosphate fertilizers in mobilizing arsenic
in areas of arsenical pesticide application and high groundwater arsenic concentrations, evaluate geologic sources
of arsenic in Texas, and target geographic areas of domestic drinking-water wells potentially affected by high
arsenic levels. This study began in November 2004 and will continue through August 2005. BEG will conduct a number
of tasks to accomplish this objective. (1) This study will include a review of arsenic levels in surrounding
states and an evaluation of research related to elevated arsenic in groundwater nationwide. (2)
Potential anthropogenic sources of arsenic, such as arsenical pesticides in the Southern High Plains and the
Southern Gulf Coast, will be examined using GIS overlay analyses and soil sampling. The ability of phosphate
fertilizers to mobilize arsenic from arsenical pesticide applications will also be evaluated, when information
on phosphate fertilizer application can be obtained. (3) Potential geologic sources of elevated arsenic
concentrations in groundwater in Texas will be evaluated using relationships between arsenic concentrations
and different geologic units. Relationships between arsenic concentrations and other ions, particularly uranium
and oxyanions, will be evaluated using existing databases to determine geologic rather than anthropogenic sources
of arsenic. The impact of different redox conditions on the distribution of arsenic will also be examined.
Limited additional groundwater sampling will be conducted where
necessary and feasible. Materials will be developed for technology transfer for interested agency staff.
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