Saturday, 15 July 2006

Fate, Transport, and Bioavailability of Arsenic in Poultry Amended Soils.

Sheila Gardner and J. Thomas Sims. Univ of Delaware, 152 Townsend Hall, Newark, DE 19716

Arsenic (As) contamination of groundwaters is an emerging issue on the Delmarva Peninsula primarily because of the long-term application of poultry litter as a fertilizer. Roxarsone (3-nitro-4-hydroxyphenyl arsenic acid) has been added to poultry feed for decades to control Coccidiosis and act as a growth promoter. Since roxarsone is excreted by chickens, it is directly applied to cropland where it is known to be converted into inorganic forms of As that are potentially toxic to humans and aquatic biota. Soils were collected from five different farms in Sussex County, Delaware with histories of poultry litter application for use in studies of As leaching and bioavailability. Soil columns (15 cm by 20 cm) were packed with topsoils from two amended sites (Corsica loam and Sassafras loamy sand) and were treated with 0, 0.448, 0.897, 1.345, 1.793, and 2.242 kg m-2 poultry litter and leached weekly. Leachate was collected and analyzed for As by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and Graphite Furnace Atomic Absorption Spectrometry (GFAAS). Upon completion of the leaching study, soil from each column was analyzed for bioavailable As (Mehlich 3 and Physiologically-Based Extraction Test) and potentially leachable As (Water Soluble, Toxicity Characteristic Leaching Procedure, and Synthetic Precipitation Leaching Procedure). An incubation study was also performed to mimic the column leaching study. Samples were taken at 0, 21, and 48 days and were analyzed for bioavailable and leachable As.

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