Soil has been identified as a significant source of lead (Pb) exposure for both children and adults. Therefore, identifying possibly contaminated soils by soil testing is important to protect public health. Soil Pb test results are usually reported as total Pb (in milligrams per kilogram), carried out using a concentrated nitric acid (HNO3) digestion procedure by hot plate (Environmental Protection Agency (EPA) method 3050) or microwave (EPA method 3051) followed by inductively coupled plasma atomic emission spectrometry to determine total Pb in the digest. However, this procedure is both time consuming and expensive, sometimes costing homeowners and gardeners more than $50 per sample. To make soil Pb testing more economically accessible to homeowners and gardeners, several university soil-testing laboratories offer less expensive screening tests designed to estimate total soil Pb. The first objective of this study was to compare three commonly used screening tests, modified Morgan, Mehlich 3, and 1 M HNO3, with the standard total Pb testing method (EPA method 3051) to find which extractant is the most reliable predictor of total Pb. The second objective was to investigate the effect that different degrees of soil grinding have on the total Pb test and the extracted Pb concentration measured from the 1-M HNO3 test. Results indicate that the strongest predictor of total Pb is 1 M HNO3 followed by Mehlich 3 and modified Morgan, and that thorough grinding is necessary if using less than 5 g of soil in a Pb test to adequately homogenize Pb-contaminated samples and achieve acceptable testing reproducibility.
1Department of Crop and Soil Sciences, Cornell University, 817 Bradfield Hall, Ithaca, NY. Ms. Sarah E. Wharton is corresponding author.
2Department of Crop and Soil Sciences, Cornell University, 818 Bradfield Hall, Ithaca, NY.
3Center for Environmental Health, New York State Department of Health, Troy, NY.
4Department of Crop and Soil Sciences, Cornell University, 910 Bradfield Hall, Ithaca, NY.
Address for correspondence: Mr. Murray B. McBride, Department of Crop and Soil Sciences, Cornell University, 817 Bradfield Hall, Ithaca, NY 14853, USA; E-mail: email@example.com
Financial Disclosures/Conflicts of Interest: This study was funded by the National Institutes of Health and the National Institute of Environmental Health Sciences (Grant No. 15R21ES017921).
Received May 29, 2012.
Accepted for publication October 3, 2012.