Passive diffusion samplers have been tested at a number of sites where volatile organic compounds (VOC?s) are the principal contaminants in ground water. Test results generally show good agreement between concentrations of VOC?s in samples collected with diffusion samplers and concentrations in samples collected by purging the water from a well. Diffusion samplers offer several advantages over conventional and low-flow ground-water sampling procedures:
? Elimination of the need to purge a well before collecting a sample and to dispose of contaminated water.
? Elimination of cross-contamination of samples associated with sampling with non-dedicated pumps or sample delivery tubes.
? Reduction in sampling time by as much as 80 percent of that required for ?purge type? sampling methods.
? An increase in the frequency and spatial coverage of monitoring at a site because of the associated savings in time and money.
The successful use of diffusion samplers depends on the following three primary factors: (1) understanding site conditions and contaminants of interest (defining sample objectives), (2) validating of results of diffusion samplers against more widely acknowledged sampling methods, and (3) applying diffusion samplers in the field.