SAMPLING BIAS CAUSED BY MATERIALS USED TO MONITOR HALOCARBONS IN GROUNDWATER

Laboratory experiments were conducted to evaluate materials used in the construction of groundwater monitors for their potential to cause sampling bias. Ten materials were exposed to low concentrations of five halogenated hydrocarbons in water for periods up to 5 weeks. Borosilicate glass was the only material that did not diminish the halocarbon concentrations. Three metals, including stainless steel, apparently transformed the compounds. Six synthetic polymers, including poly(tetrafluoroethylene) and rigid poly (vinyl chloride), absorbed the compounds. The sorption rates were dependent on flexibility of the polymer, water solubility of the compound, solution volume to polymer surface area ratio, and temperature. A diffusion model explained the concentration histories of solutions exposed to polymers, and the diffusion mechanism was confirmed by direct measurement of halocarbon distributions in several of the polymers. The experimentally determined diffusivities and polymer–water partition coefficients for polyethylene were consistent with literature data. © 1990, American Chemical Society. All rights reserved.