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United States Department of Agriculture

Agricultural Research Service

Research Project: PLANT VARIATION IN CD, PB, ZN AND AS ACCUMULATION AND BIOAVAILABILITY AND METHODS TO LIMIT RISK Title: Long-Term Effects of Lime, Phosphorus and Iron Amended Orchard Soils on In Vitro, Water and Nitric Acid Extractable Lead

Author
item Codling, Eton

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 14, 2007
Publication Date: October 1, 2007
Repository URL: http://hdl.handle.net/10113/9639
Citation: Codling, E.E. 2007. Long-Term Effects of Lime, Phosphorus and Iron Amended Orchard Soils on In Vitro, Water and Nitric Acid Extractable Lead. Soil Science. 172:811-819.

Interpretive Summary: Lead arsenate was used in orchards as an insecticide for over 60 years. Consequently, orchard soils are contaminated with lead. Extraction methods such as water, nitric acid and in vitro have been used to determine soluble lead in soils contaminated by lead paint and leaded gasoline. These methods have not been used to determine lead solubility when orchard soils are amended with lime, phosphorus and iron, which are expected to reduce Pb solubility. The objective of this study was to determine the effects of lime, phosphorus and iron amendments on water, nitric acid and in vitro (glycine) extractable Pb in two orchard soils over time. The use of phosphorus is not recommended as a reliable lead remediation strategy in soil with high iron content. One molar nitric acid is not an ideal extractant in determining Pb bioavailability due to the strong oxidizing capability. Lime, Fe and P amendments did not reduce bioavailability risk below the proposed maximum level of 100 microgram for infants. Further studies are warranted to evaluate the effects of other amendments on water and glycine extractable Pb in orchard soils.

Technical Abstract: Lead arsenate was used in orchards from about 1900 to 1960. Consequently, orchard soils are contaminated with lead. Extraction methods such as water, nitric acid and in vitro have been used to determine soluble lead in soils contaminated by lead paint and leaded gasoline. The solubility of Pb in lead arsenate contaminated soils, however, has not been determined by these methods when orchard soils are amended with lime, phosphorus and iron, which is expected to control Pb bioavailability. The objective of this study was to determine the effects of lime, phosphorus and iron amendments on water, 1 M HNO3 and in vitro (0.4 M glycine) extractable Pb in two orchard soils over time. The use of P as KH2PO4 is not recommended as a reliable lead remediation strategy in soil with high iron content. One molar nitric acid is not an ideal extractant in determining Pb bioavailability due to the strong oxidizing capability. Lime, Fe and P amendments did not reduce bioavailability risk below the proposed maximum level of 100 microgram for infants. Further studies are warranted to evaluate the effects of other amendments on water and glycine extractable Pb in orchard soils.

Last Modified: 4/17/2014
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