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Long-term integrating samplers for indoor air and sub slab soil gas at VI sites
Citation:
Lutes, C., R. Uppencamp, H. Hayes, R. B. MOSLEY, AND D. J. GREENWELL. Long-term integrating samplers for indoor air and sub slab soil gas at VI sites. In Proceedings, Vapor Intrusion 2010, Chicago, IL, September 29 - 30, 2010. AWMA, Pittsburgh, PA, ,, (2010).
Impact/Purpose:
conference paper
Description:
Vapor intrusion (VI) site assessments are plagued by substantial spatial and temporal variability that makes exposure and risk assessment difficult. Most risk-based decision making for volatile organic compound (VOC) exposure in the indoor environment is based on health benchmarks (toxicity values). However the most common approach to indoor air assessment in the industry is comparison of a limited number of one day integrated Summa canister data to benchmarks based on 1 to 30 years of exposure. Subslab soil gas sampling methods for VOCs normally collect small volume samples actively over 2 to 15 minutes (rarely 24 hour periods). The variance in differential pressure alters the flow direction across the slab, potentially dramatically changing the concentration in the immediate subslab region near cracks. Existing passive soil gas sampling methods are not considered to be quantitative because of the difficulty of establishing diffusion and thus uptake rates when the sampler is in direct contact with the soil. Proof of concept experiments have been conducted at two sites on an innovative subslab soil gas sampler. This sampler couples passive media that give good performance in indoor environments with a simple chamber refreshed by a continuous flow of subslab soil gas. The sampler integrates both over time and space. The performance of this innovative integrating subslab sampler is compared here to established methods of analysis.
