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Using the Mehlich-3 Soil Test as an Inexpensive Screening Tool to Estimate Total and Bioaccessible Lead in Urban Soils
Citation:
Minca, K. K., N. T. Basta, AND K. G. Scheckel. Using the Mehlich-3 Soil Test as an Inexpensive Screening Tool to Estimate Total and Bioaccessible Lead in Urban Soils. Dennis Corwin (ed.), JOURNAL OF ENVIRONMENTAL QUALITY. American Society of Agronomy, MADISON, WI, 42(5):1518-1526, (2013).
Impact/Purpose:
Recently, large-scale urban redevelopment and demolition of abandoned housing has created large areas of vacant land in old industrial cities in the United States, including Cleveland, OH, Detroit, MI, and Chicago, IL. City planners, community groups, and other stakeholders seek to convert some of the newly created vacant land into urban agriculture and gardening, parks, playgrounds, and other common areas. Because this type of land use involves high amounts of exposure to the soil, it is important to assess historical legacy soil contaminants in these areas before redevelopment. Chaney et al. (2011) recently showed bioaccessible Pb may be low in long- term garden soils. They recommended bioaccessible Pb be measured to make adjustments for Pb bioavailability when determining the suitability of an urban soil for food production. Bioaccessible Pb extractions using a modified RBALP have similar pH as Mehlich-3 extraction solution. Thus, Mehlich-3 soil test may provide a simultaneous estimate of bioaccessible Pb and total Pb. To our knowledge, the ability of Mehlich-3 to predict bioaccessible Pb and estimate the bioavailability of Pb via soil ingestion has not been reported. The objective of this study is to evaluate Mehlich-3 to estimate total Pb and bioaccessible Pb in urban soil from residential vacant lots. We also propose a soil assessment protocol for using Mehlich-3 soil test to determine suitability of residential vacant lots for food production based on risk for soil ingestion.
Description:
In cities nationwide, urban agriculture has been put on hold because of the high costs of soil testing for historical contaminants such as lead (Pb). The Mehlich-3 soil test is commonly used to determine plant available nutrients, is inexpensive, and has the potential to estimate trace metals in urban soil. The objectives of this study are to evaluate the ability of the Mehlich-3 to estimate total Pb and bioaccessible Pb in vacant residential lots. Total and bioaccessible Pb were determined in 68 vacant residential lots in Cleveland, OH, using standard USEPA Methods 3051A and the Relative Bioaccessibility Leaching Procedure (RBALP), respectively. The Mehlich-3 soil test was used to determine extractable Pb, and the results show Mehlich-3 was strongly correlated with total and bioaccessible Pb. The Mehlich-3 soil test could be used as a screening tool to not only estimate total Pb (slope 1.73, r2 = 0.970) but also to estimate bioaccessible Pb when using RBALP at pH 1.5 (slope 1.67, r2 =0.975) and RBALP at pH 2.5 (slope 1.15, r2 = 0.938). Additional samples were collected from the Thackeray Avenue site in Cleveland, OH, to demonstrate the ability of the Mehlich-3 soil test to screen soil for Pb. The results from the Thackeray site show good agreement between Mehlich-3 and the standard USEPA methods. A screening protocol for urban vacant residential lots using the Mehlich-3 soil test is proposed.
