Measurement of the vapor flux from volatile organic compounds (VOCs) provides a rapid means for screening large areas of potential contamination. The vapor flux is determined from the rate of VOC concentration buildup inside a 3.1L accumulator device that is sealed to the surface of the contaminated soil. After the VOC concentrations are allowed to increase for a few minutes, they are analyzed with a portable gas chromatograph or a total organic vapor analyzer.
The measurement approach was evaluated at a field site in an area where the ground water and soil had been impacted with Jet Fuel No. 4 (JP-4). An indication of the areal extent of impact was determined by mapping the surface VOC vapor flux. The pattern revealed by the flux measurements was found to coincide, in rough outline, with the known extent of toluene concentrations in the ground water and with conventional soil-gas survey results. In addition, a mathematical model describing VOC diffusion into the accumulator device was verified by performing laboratory measurements of the surface VOC vapor flux on a sandbox designed to simulate a hazardous waste site.