ESN Northwest

Passive Sampling

Passive Sampling is preferred when active vapor sampling does not yield an optimum sample because the sample is obtained on an instantaneous basis. When groundwater is extremely deep, when soils are very tight all the way to groundwater or when semi-volatile hydrocarbons are targeted, it is often more effective to sample passively using ESN's VaporTec® sampler.

Passive sampling accumulates a vapor sample while the sampler is left exposed in the ground. Once a steady state condition is reached, for example three days to two weeks, the sampler is removed from the ground and sent to the lab for analysis. The process requires more time and often two field visits but in extreme conditions generates valuable data at costs less than conventional drilling.

Passive samplers consist of sealed 40mL glass vials containing an activated sorbent mounted for optimum exposure to vapors. When the seal is removed, the sampler is inserted in a shallow hole (6" x 1.5") in the ground. The soil is then replaced on top of the sampler. When the exposure reaches a steady state, the sampler is removed, sealed, numbered, and returned to the lab for analysis.

Trip blanks accompany all samplers into and out of the field. Additionally, sampling duplicates are supplied as specified in the scope of work.



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