Bioavailability of Arsenic in Pesticide-Applied Cotton Soils of Texas
Years of widespread application of arsenic-based pesticides have increased the background concentrations of As in certain agricultural soils, such as in the cotton fields of Texas, where arsenical compounds were applied for defoliation during harvest. Due to rapid encroachment of suburban development on former agricultural lands in fast expanding cities, soil ingestion by children from incidental hand-to-mouth activity is now an important issue in assessing human health risks associated with exposure to this Group-A carcinogen. Human health risk from ingested arsenic is generally associated with those geochemical forms of arsenic that are soluble in gastric and intestinal juices and are potentially absorbed by the intestinal membrane. We have developed an appropriate “in-vitro” technique that has the capability of simulating human bioavailability of arsenic. An incubation study is currently in progress to dissect the relationship between soil-speciation of arsenic and arsenic bioavailability in the Houston Black soil series (the state soil of Texas, most commonly used for growing cotton) amended with one inorganic and one organic arsenical pesticide using our in-vitro model. A sandy soil from the Immokalee series with minimal arsenic retention capacity is used as the control to identify the effect of soil properties on arsenic speciation, hence, bioavailability. The soils have been amended with the arsenical compounds at 3 rates, representing normal, high, and excessive pesticide application. Concentrations of arsenic are to be measured using a graphite furnace atomic absorption spectrometer at 3 times, immediately after pesticide application, after 6 months, and after one year of soil-pesticide equilibration.
Environmental Geology and Geochemistry (DEG/EMD)
AAPG Annual Meeting 2004: Embrace the Future, Celebrate the Past Technical Program