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Update on Diffusive Sampling of Volatile Organic Compounds on Carbopack X and Carbograph 5TD
Citation:
Whitehill, A. Update on Diffusive Sampling of Volatile Organic Compounds on Carbopack X and Carbograph 5TD. Air & Waste Management Association Air Quality Measurements Methods and Technology, Durham, NC, November 14 - 16, 2023.
Impact/Purpose:
This study addresses the development and validation of passive / diffusive sampling methodology for air toxics compounds. We test the diffusive uptake rates of a selection of volatile organic compounds / air toxics compounds on both Carbopack X and Carbograph 5TD thermal desorption tubes. We perform tests at different sampling durations and environmental conditions (e.g., relative humidities, etc.). These results will help to validate and expand EPA Method 325A/B to additional toxic compounds and sorbent types to provide additional options for industry, regulators, and community groups for fenceline or community monitoring of hazardous air pollutants.
Description:
United States Environmental Protection Agency (EPA) Method 325A/B describes the collection (Method 325A) and analysis (Method 325B) of volatile air toxics compounds by passive or diffusive sampling on thermal desorption (TD) tubes. Method 325B lists diffusive uptake rates (DURs) for 18 volatile organic compounds (VOCs) (Table 12.1 of Method 325B), mostly based on the 24-hour sampling results of McClenny et al. (2005) onto CarbopackTM X. The method has been further evaluated for a subset of eight of those compounds by a sample integrity and interlaboratory comparison study by Oliver et al. (2017). Additional validation will support the expansion of EPA Method 325A/B to additional types of industrial facilities, as well as additional compounds, sorbents, and sampling durations. Using Method 325B Appendix A as a guide, we performed a series of chamber exposure experiments to measure DURs for a subset of air toxics compounds onto standard CarbopackTM X and CarbographTM 5TD thermal desorption tubes. We discuss preliminary results from the determination of DURs as a function of sampling duration (24 hours to 2 weeks), sorbent type (CarbopackTM X versus CarbographTM 5TD), and sampling conditions (such as relative humidity). These results will guide future regulatory monitoring efforts, as well as aid community and environmental groups with exposure assessment and monitoring in environmental justice (EJ) regions. References: McClenny et al. (2005). Journal of Environmental Monitoring, 7(3), 248-256. Oliver et al. (2017). Atmospheric Environment, 163, 99-106.