There continues to be an increased application of the incremental sampling methodology to other environmental chemicals of concern (e.g., inorganics, polycyclic aromatic hydrocarbons [PAHs], polychlorinated biphenyls [PCBs], dioxins, volatiles, semi-volatiles, pesticides, etc.) despite the lack of rigorous data validation studies for these constituents similar to those utilized for explosives prior to the release of Environmental Protection Agency (EPA) Method 8330B. To date, there are no other EPA-approved methods that include incremental sampling processing. Thus, the objectives of this project are to fill the necessary data gaps for applying incremental sampling methodology (ISM) processing of soils for PAH analysis.
This study will involve the distribution and analysis of soils that are fortified with various PAH surrogate compounds. Multiple replicates will be utilized to provide a statistically robust data set. At least five laboratories already accredited for PAH analysis by the DoD Environmental Laboratory Accreditation Program (ELAP) will be utilized for this project. The precision and bias acceptance criteria will be included in the next version of the Environmental Data Quality Workgroup Quality System Manual:
- Bias: Calculate criteria for surrogate recoveries with and without drying/milling.
- Precision: Calculate criteria for surrogate replicate relative standard deviations and define minimum number of replicates and number of increments when drying/milling is and is not performed.
There will be two phases to this study. Phase 1 will consist of supplying the laboratory with four pre-spiked and homogenized 1-kg soil samples and one 1-kg un-spiked (blank) soil sample, for a total of five 1-kg samples (four pre-spiked and one blank). Each of the pre-spiked samples, in its entirety (1-kg), shall be processed as follows:
- Treatment 1 - no milling or drying
- Treatment 2 - 5 x 1 minute milling and no drying
- Treatment 3 - 16-24 hour ambient drying and no milling
- Treatment 4 - milling and drying (as above)
- Blank - milling in the same puck mill used for Treatments 2 and 4 immediately after processing each of Treatments 2 and 4
Each of the four treatments above shall be analyzed by SIM for PAHs as 10 replicates, each consisting of 30 increments (2-D Japanese slabcake ISM). The final mass of each replicate shall be 15-20 grams. The two milling blanks shall also consist of 30 increments. Total number of samples for PAH analysis is therefore 42 (40 Treatments and 2 Milling Blanks).
Phase 2 will consist of supplying the laboratory with two 1-kg of blank soil samples, and two 25-g surrogate fortification vials containing all 4 surrogates. The laboratory shall fortify each kilogram of blank soil with 25 grams of the surrogate solution before blending, weighing, and spreading soil out to perform two-dimensional slabcake ISM subsampling. As in Phase 1, 10 replicates will be produced for each sample. One spiked sample will consist of 10 replicates 30 subsampling increments each, and the other will consist of 10 replicates of 50 subsampling increments each. The final mass of each replicate shall be 15-20 grams. Samples will be analyzed by SIM for PAHs.
This will result in a total of 20 samples for analysis for this Phase 2. The intent of Phase 2 is to determine if variability can be reduced by increasing the number of increments.
This study will provide information to fill the necessary data gaps for applying ISM processing of soils for PAH analysis and establishing reliable and defensible environmental data to be paramount to site investigations.