Evaluation of Sampling and Sample Preparation Modifications for Soil Containing Metallic Residues

Abstract : Research over the last decade has revealed that energetic constituents are released into the environment as a result of military training in extremely heterogeneous patterns. Traditional soil sampling and sample preparation methodologies are inadequate to address this level of heterogeneity. Consequently, a number of necessary changes to the accepted soil sampling and sample preparation procedures, which were adopted in a revised U.S. Environmental Protection Agency (USEPA) Method 8330B are identified. Recently, there have questions about whether the above questions also substantively apply to other constituents, such as metals, semi-volatile organic compounds, and polychlorinated biphenyls. Preliminary data suggest metal residues from small arms and pyrotechnic military training are heterogeneously distributed. As a result, regulatory agencies are increasingly requiring the DOD to apply USEPA Method 8330B to the sampling and processing of soils from small arms ranges containing metals. However, there is no published research indicating whether changes to USEPA Method 3050B for metals are needed or warranted. This study assessed USEPA Method 8330B and whether it is applicable to soils containing metals. The utility of multi-increment sampling versus traditional grab/discrete sampling was assessed and found to yield reproducible and more representative metals soil concentrations. In addition, changes to the soil digestion procedure, USEPA Method 3050B, were evaluated and included the following: 1) necessity of machining or grinding of the soil, appropriate type of grinding apparatus and grinding interval; 2) assessment of the need to increase the digested mass and digestion interval; 3) optimum soil to acid ratio, i.e., digestion efficiency; 4) sub-sampling to build the digestate sample; and 5) disposition of the oversize fraction, i.e., material larger than 2 mm.