Technology Description

To reduce the influence of compositional and distributional error when estimating the mean concentration of an analyte within a decision unit, Method 8330B recommends collecting 30 or more evenly spaced increments to build a sample with a total sample mass of more than 1 kg. The objective of this sampling technique is to obtain a representative amount of every particle size, composition (e.g., Pb, As, Cu, Cr, Sb, Cd, and Zn), and configuration (e.g., spheres or elongated particles) and to not over-sample or miss any portion of the decision unit. To estimate the total uncertainty for estimating mean concentrations of munitions constituents (MC), replicate multi-increment samples must be collected. If this step is not included in a sampling plan, the total characterization error cannot be determined. To obtain representative subsamples from a field sample, the processing protocol must also address the compositional and distribution heterogeneity. The U.S. Geological Survey recommends that the entire field sample be dried, passed through a #10 (2-mm) sieve, then mechanically pulverized to reduce the particle size to less than 0.15 mm. This step is necessary because, within the less than 2-mm soil size class, particles of MC are present in a variety of sizes, densities, shapes, and compositions. The #10 sieve size encompasses those particles that dissolve more readily and is consistent with the classification of soil and sometimes is used in risk models for human exposure. In this project, multi-increment sampling and adequate sample processing will be demonstrated for the characterization of metals in soils that have been introduced as a consequence of military training activities. Comparisons will be made with existing protocols to evaluate data quality improvements.