THE FATE OF ARSENIC IN POULTRY LITTER- AMENDED FIELDS, NORTHWEST ARKANSAS

Poultry is the main industry in Northwest Arkansas and the litter from chicken houses is applied to the surface of fields as fertilizer. The Savoy Experimental Watershed (SEW) is located in Washington County, Arkansas and is used by the University of Arkansas to evaluate the impact of best-management practices on soil and water. The area is a part of a mantled karst system with many fractures enabling contaminated surface water to enter the ground-water system. The SEW had poultry litter applied two of the last three years which is average land management for the area. Poultry litter contains As Roxarsone (3-nitro-4-hydroxyphenylarsonic acid) which is introduced into the environment at the rate of approximately 10⁶ kg/year nationally. The EPA, in order to reduce health risks, has introduced a maximum contamination level of 10µg/L for public drinking water. Much of the As in the ground water of Arkansas is currently within the EPA limits but the input of Roxarsone has not been ascertained. A project to obtain preliminary data and to screen samples for ICP-MS analyses of arsenic was conducted in and around a small instrumented site measuring 20 by 100m (rainfall, lysimeters, shallow wells, microweirs, and spring discharge) within the SEW. Six lysimeters, five spring and three runoff water samples were analyzed using a Hach(tm) As test kit. All of the water samples were below the detection limit of about 10µg/L. Eleven 2-6 cm deep Nixa (loamy residual from cherty limestone) and Captina (silty material and underlying colluvium from cherty limestone) soil samples taken from the same area yielded concentrations of 3-7 mg/kg. It appears that the majority of the As is retained in the soils and major amounts of As are not introduced into the ground or surface water.