It should be noted that some soil types have been shown to exhibit significant degradation of aromatic VOCs in less than 48 hours (Hewitt, et. al., 1999, Environmental Testing and Analysis). Also, Sorini, et. al., (2002, Soil Sediment & Water) observed significant differences between samples that were extruded directly into methanol and samples where methanol was added at a later time to soil extruded into empty VOA vials (where methanol was added through the septum). Based on these findings, where project or program DQOs require a higher degree of accuracy soil samples may need to be chemically preserved.
