Quantitative passive soil vapor sampling for VOCs--part 1: theory

Area of Science:

• Environmental Science
• Geochemistry
• Analytical Chemistry

Background:

• Volatile organic compounds (VOCs) are key contaminants at hazardous waste sites.
• Soil vapor sampling is crucial for assessing contamination extent and type.
• Traditional active sampling methods face challenges with low-permeability soils and leaks.

Purpose of the Study:

• To develop mathematical models for radial vapor diffusion to a drilled hole.
• To establish quantitative relationships for passive soil vapor sampling.
• To provide a basis for improved passive sampler design and application.

Main Methods:

• Development of transient and steady-state mathematical models for vapor diffusion.
• Analysis of passive sampler sensitivity and practical sampling durations.
• Consideration of soil moisture conditions and uptake rates.

Main Results:

• Mathematical models for radial vapor diffusion were established.
• Quantitative relationships between sorbed mass, vapor concentration, and sampling time were determined.
• Optimal uptake rates (0.1-1 mL/min) were identified to minimize starvation effects.

Conclusions:

• Passive soil vapor sampling can be quantitatively reliable with appropriate modeling.
• The findings support enhanced passive sampler design for accurate risk assessment.
• This research improves the assessment of VOC contamination in soil vapor.