Saturday, 15 July 2006

Total and Extractable Lead and Arsenic Concentrations in US Long-Term Orchard soils.

Eton E. Codling1, Carrie E. Green1, R. L. Chaney2, and Andy K. Piri3. (1) USDA-ARS, 10300 Baltimore Avenue, BARC-West, Bldg. 007, Beltsville, MD 20705, (2) USDA-ARS-ANRI, Bldg. 007, BARC-West, 10300 Baltimore Ave., Beltsville, MD 20705, (3) USDA-NRCS, 708 Lisbon Center Dr. Suite E, Woodbine, MD 21797

Lead arsenate was used as an insecticide in the U.S. from 1900 to 1950 to control Codling moth (Cydia pomonella)in apple orchards. As a result these soils are contaminated with lead (Pb) and arsenic (As). Concerns have been raised about conversion of land use of such Pb and As rich soils, either for vegetable crops or for housing development. Some information has been published about Pb and As in orchard soils, but the extent of variation in As and Pb concentrations from old orchards throughout the United States are not known. The objectives of this study were to determine the 1) 1N HNO3 extractable As and Pb in orchards soils from six States and 2) the in vitro bioaccessible of Pb levels in these soils. Orchard soils were collected from several sites in Maryland (MD), Michigan (MI), New York (NY), Virginia (VA), West Virginia (WV) and Washington (WA). Soils were extracted with 1N HNO3 with 1hr of shaking. Lead concentrations ranges were 11-1966, 1410, 1487, 109-761, 93-806 and 77-3859 mg kg-1 for MD, MI, NY, VA, WV and WA respectively. Arsenic concentrations were 0.14-309, 262, 268, 0.03-99, 3.8-52 and 11-1346 mg kg-1 respectively. The in vitro extractions for Pb were conducted using a 0.4 M glycine solution, adjusted to pH 2.0 with 0.1 M HCl. A significant fraction of the orchard soils exceeded the 400 mg kg-1 Pb levels established by US-EPA and US-HUD for bare soils adjacent to housing, and a smaller fraction exceeded the 1200 mg kg-1 Pb levels for vegetated soils adjacent to housing. A review of all findings regarding our evaluation of Pb and As risks from long-term orchard soils will be presented.

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