Laboratory evaluation of polychlorinated biphenyls encapsulation methods

Abstract

Effectiveness and limitations of encapsulation methods for reducing polychlorinated biphenyls concentration in indoor air and abating contaminated surface have been evaluated. Ten coating materials such as epoxy and polyurethane coatings, latex paint and petroleum-based paint were tested in small environmental chambers to rank encapsulants by their resistance to polychlorinated biphenyl sorption (sink chamber tests) and to determine key parameters for consideration by a barrier model. Wipe samples were collected from polychlorinated biphenyl contaminated surfaces encapsulated with coating materials to rank encapsulants by their resistance to polychlorinated biphenyl migration from the source. A barrier model was used to calculate the polychlorinated biphenyl concentration gradient in the source and encapsulant layers on exposed surfaces of encapsulants and in room air at different times. The performance of encapsulants was ranked by those concentrations and polychlorinated biphenyl percentage reductions. Overall, the three epoxy coatings performed better than other coatings. Both experimental results and mathematical modelling showed that selecting proper encapsulants can effectively reduce polychlorinated biphenyl concentrations on exposed surfaces. The encapsulation method could be an effective short-term abatement technique for containing emission of low levels of polychlorinated biphenyls from contaminated surfaces. Barrier models are useful tools for ranking the relative performances of encapsulants once their material/material K1,2, material/air partition coefficients ( Kma) and solid-phase diffusion coefficients ( Dm) are obtained.