In Situ Equilibrium Polyethylene Passive Sampling of Soil Gas VOC Concentrations: Modeling, Parameter Determinations,...

Area of Science:

• Environmental Science
• Analytical Chemistry
• Geochemistry

Background:

• Volatile organic compounds (VOCs) in soil gas are critical environmental contaminants.
• Accurate quantification of VOCs in unsaturated subsurface environments is challenging.
• Traditional methods may involve complex sampling or inaccurate equilibrium models.

Purpose of the Study:

• To evaluate low-density polyethylene (PE) sheets as passive soil gas samplers for VOCs.
• To develop and validate methods for quantifying VOCs within PE material.
• To determine key chemical properties influencing PE-based VOC sampling.

Main Methods:

• Modeling and benchtop testing were employed.
• Determined PE-water (KPEw), PE-air (KPEa) partition coefficients, and PE diffusivity (Dpe).
• Benchtop batch tests with contaminated soils were conducted to compare PE-derived concentrations with traditional methods.

Main Results:

• PE-water, PE-air partition coefficients, and diffusivity values were determined and found consistent with existing data.
• Field equilibration times for VOCs using 70-100 μm PE sheets were estimated to be less than 1 day.
• PE-based soil air concentrations closely matched those derived from water and headspace gas analyses in benchtop tests.

Conclusions:

• Low-density polyethylene sheets are effective passive samplers for soil gas VOCs.
• PE-based measurements offer a reliable alternative, avoiding overestimations from traditional equilibrium partitioning models.
• This method enhances accuracy in assessing subsurface volatile organic compound contamination.