The Effect of Soils on the Permeation of Plastic Pipes by Organic Chemicals

Abstract

Polybutylene pipes (0.75 in.) buried in both water‐saturated and unsaturated soils contaminated with toluene, trichloroethylene, 1,2‐dichlorobenzene, and o‐chlorophenol were permeated to detectable levels in 1 to 150 days, depending on the organic chemical and its concentration. Comparison of these results with pipe‐bottle experiments containing no soil showed that the concentration of organic chemical in the soil pore controls the rate of organic chemical permeation through buried plastic pipes. The results also indicate that under otherwise identical conditions, plastic pipes buried in a soil of high organic carbon content will be permeated more slowly than pipe buried in a soil of low organic carbon content. Even so, soils of very high organic carbon content cannot be relied on to protect plastic pipe from permeation by organic chemicals. A method for predicting the equilibrium concentration of organic chemical in the soil pore was useful in determining whether a plastic pipe buried in contaminated soil is likely to be permeated.

Permeation of BTEX compounds through HDPE pipes under simulated field conditions

“…Four levels of gasoline-contaminated soil were prepared by spiking 1 kg of the sand-topsoil mixture with known amounts of premium gasoline and mixing the soil by rotating the soil container for one week. The volumetric moisture content of the soil was adjusted to approximately 10%, which was above the water content of soils equilibrated at a relative humidity > 98% (Holsen et al, 1991b). The amounts of BTEX sorbed onto the four soils were determined using methanol extraction and analyzed by gas chromatography.…”

“…The case of benzene demonstrates that knowledge of environmental fate and transport is essential for evaluating the potential permeation risk of contaminants because the distribution of chemicals among environmental media determines the contaminant levels that plastic pipes might encounter in the field. In the unsaturated soil, plastic pipe permeation was believed to occur from the vapor phase (Holsen et al, 1991b;Park et al, 1991). The current study did not collect vapor samples for BTEX analysis, and thus the exact concentration of BTEX in soil gas was unknown during the experimental period.…”

“…Park and co-workers (1991) reported that organic chemicals that do not readily permeate PB pipes when present alone can have their permeability enhanced considerably when they are mixed with highly permeable organic chemicals. In addition, soil type and characteristics may have a significant effect on the permeation of organic compounds through pipe materials by implicitly determining the effective availability for permeation (Holsen et al, 1991b).…”

“…The losses were mainly attributable to sorption/diffusion into the pipe and volatilization. Generally, the diffusion coefficients of organic compounds in the vapor phase through soil pores are several orders of magnitude larger than the diffusion coefficients through plastic pipes (Holsen et al, 1991b). Therefore, the mass transfer in soils may be rapid enough to hinder the development of a concentration gradient in the soils.…”

Are There Health Risks from the Migration of Chemical Substances from Plastic Pipes into Drinking Water? A Review

“…These volatile organic compounds (VOC) can readily diffuse through plastic pipe and migrate into water within the pipe. Holsen et al (1991) have reported permeation incidents in connection with plastic piping materials at abandoned industrial sites, near bulk chemical storage tanks and electroplating facilities, as well as at residential sites (e .g., adjacent to or near storage tanks at service stations or dry cleaning operations). If sustained, contact with these VOCs may permanently degrade the integrity of the pipes.…”