Comparison of Soil Tests for Screening Soils for Heavy Metal Contamination.

Growing awareness of the health risks associated with exposure to environmental pollutants has resulted in an increased demand by the general public for environmental soil testing. In order to minimize any risk to themselves or their families, homeowners often look at the soil around their homes and in their gardens as potential sources of risk and request soil tests to “screen” their soil for contamination with heavy metals, pesticides or other compounds.  A number of standard methods exist for measuring contaminants in soils, but these methods are often intensive and cost prohibitive for widespread use. In many cases, these environmental tests are not offered by “traditional” soil testing laboratories.  The ability to use less intensive and/or less costly tests to “screen” samples for contamination is a desirable alternative that would allow for greater use provided the “screening method” can reliably identify those soils where contamination is truly a concern.

In this study, three “quick tests” (1N Nitric Acid, Mehlich 3 and Mehlich 1) were compared with the standard method EPA3051 as screening tests for six metals (As, Cd, Cr, Ni, Pb and Zn).  Previous work has shown that the 1N nitric acid test is a good predictor for EPA3051-Pb, but less data is available for the other metals. The Mehlich 3 and Mehlich 1 are routine soil tests commonly used in the Mid-Atlantic region and elsewhere in the US. The ability to use these tests as a “screening” tool would be a plus for laboratories already using them as it would enable the laboratory to screen soils without requiring an additional test be added to their protocols. Ten “standard soils” (e.g., NIST and other crms) and fifty soils from Delaware and nearby states were included in the study. Data including metal content, percent recovery, soil properties and regression analysis will be presented along with a discussion of relevant issues.