6.2.2.2 Bulk sample mass reduction via sample splitting

Bulk sample splitting is not recommended. The limitations should be addressed during systematic planning if these techniques are to be considered.Bulk sample splitting is not recommended and its limitations should be addressed during systematic planning if these techniques are to be considered. Paired ISM sample collection is generally recommended over bulk ISM sample splitting when different sample processing treatments will be needed. Paired ISM samples are collected at similar increment locations and intended for different sample processing and analysis. Paired ISM samples allow separate sample processing procedures to be conducted without the uncertainty introduced through bulk splitting. The error introduced by splitting prior to the completion of sample processing can be large when the COPC “nugget” effect is large, such as in highly heterogeneous samples. Note that bulk sample splitting (or subsampling) without particle size reduction merely increases the fundamental error (FE).

Splitting the bulk ISM sample into two or more portions may be necessary if only one ISM sample is collected and two (or more) different sample handling processes are required to optimize for different contaminants. For example, targeting both explosives and SVOCs from subsurface samples requires air-drying prior to the explosives sample preparation, but air-drying may not be appropriate prior to SVOC analysis due to the potential volatilization losses of the lighter, low-boiling-point compounds. It is recommended that these techniques be performed in a controlled laboratory setting. If appropriate, splitting of an unprocessed bulk ISM sample may be accomplished with alternative shoveling, fractional shoveling, cone and quartering, or other splitting or subsampling techniques that may be appropriate depending on the nature of the soil matrix, contaminant, and DQOs (see Section 6.2.2.7). These techniques may not always be effective (Gerlach and Nocerino 2003; Petersen, Dahl and Esbensen 2004; Gerlach et al. 2002). Splitting of an unprocessed bulk ISM sample is not recommended for solid, particulate type contaminant (e.g., energetic, metals from firing ranges, etc.), as discussed below.

These bulk sample mass reduction techniques might compromise subsample representativeness when the sample is highly heterogeneous (e.g., explosives on training ranges or sample particles with a wide range of density or size). The techniques also increase the FE. Collecting duplicate ISM samples is generally more appropriate than trying to split a single ISM sample. These issues should be evaluated and addressed as part of project planning and DQO process. Specifically, reference Sections 6.2 and 6.3, as well as Sections 2 and 3 of this document as applicable, for ISM considerations that should be evaluated as part of the DQO decision process.