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United States Department of Agriculture

Agricultural Research Service

Research Project: PLANT AND SOIL FACTORS THAT INFLUENCE BIOAVAILABILITY OF HEAVY METALS IN CROPS

Location: Crop Systems & Global Change

Title: Effects of distance and depth on total and bioaccessible lead in soils from two farmhouses in Beltsville, Maryland

Author
item CODLING, ETON

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 13, 2013
Publication Date: August 5, 2013
Citation: Codling, E.E. 2013. Effects of distance and depth on total and bioaccessible lead in soils from two farmhouses in Beltsville, Maryland. Communications in Soil Science and Plant Analysis. 44:2678-2690.

Interpretive Summary: Renewed emphasis on home gardening by First Lady Michelle Obama has brought about a renewed concern regarding the potential of direct and indirect ingestion of lead by humans. The main effects of lead toxicity in humans are neurological impairment in children and hypertension in adults. Horizontal and vertical movement of lead around houses with histories of lead paint use has been studied, but the fraction of lead that will potentially impact the at risk populations (bioaccessiblity) as a function of distance and depth from the house needs to be investigated. The objective of this study was to determine the effects of distance and soil depth on total and bioaccessible lead from two houses with histories of lead paint use. Samples were collected at 0.5, 2.0, 4.0 and 10 meters from the foundation and at soil depths of 2.5, 7.5, 15 and 30 centimeters at house 1, and at two distances and five depths at house 2. Total and bioaccessible lead were extracted with 1 normal nitric acid and 0.4 molar glycine hydrochloride respectively. Total lead ranged from 303 to 2,900 milligram per kilogram at house 1 and from 704 to 9,375 milligram per kilogram at house 2 which are extremely high. Total and bioaccessible lead concentrations were highest at a distance of 0.5 meter and at a depth of 2.5 centimeter for both houses. Because of the lower total and bioaccessible lead with increasing distance and depth, it is possible to remediate these soils by removing soil from the top 7.5 centimeter and replacing it with clean soil before planting vegetable crops.

Technical Abstract: Renewed interests in home gardening heighten the concern of human lead exposure. Negative effects of lead on human health are well known. Horizontal and vertical movement of lead (Pb) around houses has been studied, but Pb bioaccessiblity as a function of distance and depth from the house needs to be investigated. The objective of this study was to determine the effects of distance and soil depth on total and bioaccessible lead from two houses with histories of Pb paint use. Samples were collected at 0.5, 2.0, 4.0 and 10 meters from the foundation and at soil depths of 2.5, 7.5, 15 and 30 cm at house 1, and at two distances and five depths at house 2. Samples were air dried and crushed to <2.0 mm. Total and bioaccessible Pb were extracted with 1 N HNO3 and 0.4 M glycine hydrochloride respectively. Total Pb ranged from 303 ± 289 to 2,900 ± 1,532 mg kg-1 at house 1 and from 704 ± 370 to 9,375 ± 5,712 mg kg-1 at house 2. Total and bioccessible Pb concentrations were highest at a distance of 0.5 m and at a depth of 2.5 cm for both houses. In most cases, percentages of total Pb that were bioaccessible at the lowest depths were higher or equal to those of the surface soil. Because of the reduction in total and bioaccessible Pb with increasing distance and depth, it is possible to remediate these soils by removing soil from the top 7.5 cm and replacing it with clean soil.

Last Modified: 9/10/2014