Field trials of a new commercially available diffusive ground-water sampling device were conducted at two industrial properties in the Blue Ridge Province of North Carolina. The test sites have extensive monitoring well networks and more than five years of historical water quality data. Volatile organic compounds (VOCs) including purgeable aromatics (petroleum hydrocarbons) and halogens (chlorinated solvents) have impacted the ground water of the subject properties. These target compounds were used as a basis to evaluate the effectiveness of diffusive ground-water samplers.
The diffusive sampling devices consist of a polyethylene membrane capsule suspended in a flexible protective covering. They are filled with supermarket-grade distilled water, sealed, and suspended in the saturated zones of monitoring wells. Natural diffusion of VOCs from the ground water into the sampler occurred until chemical equilibrium was reached. The devices were then removed and the water within the sampler was analyzed for VOCs by standard laboratory methods.
In the field trials, data from laboratory analysis of the diffusive samples was compared with laboratory data from contemporaneous conventional bailing and sampling. The results demonstrate favorable comparison between the data sets. The diffusive samplers provide an inexpensive and accurate alternative to conventional bailing and sampling methods. The devices have been shown to be suitable for long-term ground-water quality monitoring of VOCs and may also be useful for site screening or other assessment programs.