Temporal Variability of Indoor Air Concentrations under Natural Conditions in a House Overlying a Dilute Chlorinated Solvent Groundwater Plume

• Published in: Environmental science & technology Vol. 47; no. 23; pp. 13347 - 13354
• Main Authors: Holton, Chase, Luo, Hong, Dahlen, Paul, Gorder, Kyle, Dettenmaier, Erik, Johnson, Paul C
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 03.12.2013
• Subjects: Air Pollutants - analysis; Air Pollution, Indoor - analysis; Applied sciences; Atmospheric pollution; Buildings. Public works; Environmental Monitoring; Environmental testing; Exact sciences and technology; Groundwater; Groundwater - analysis; Housing; Indoor air quality; Indoor pollution and occupational exposure; Pollution; Pollution indoor buildings; Sampling; Seasons; Solvents; Solvents - analysis; Trichloroethylene - analysis; Water Pollutants, Chemical - analysis; United States; North America; Utah; America; Multicomponent mixture; Air quality; Plume; Housing; Organic chlorine compounds; Time variation; Organic solvent; One family house; Indoor pollution; Water pollution; Soil vapor intrusion; Organic compounds; Concentration distribution; Ground water
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es4024767

Current vapor intrusion (VI) pathway assessment heavily weights concentrations from infrequent (monthly–seasonal) 24 h indoor air samples. This study collected a long-term and high-frequency data set that can be used to assess indoor air sampling strategies for answering key pathway assessment questions like: “Is VI occurring?”, and “Will VI impacts exceed thresholds of concern?”. Indoor air sampling was conducted for 2.5 years at 2–4 h intervals in a house overlying a dilute chlorinated solvent plume (10–50 μg/L TCE). Indoor air concentrations varied by 3 orders of magnitude (<0.01–10 ppbv TCE) with two recurring behaviors. The VI-active behavior, which was prevalent in fall, winter, and spring involved time-varying impacts intermixed with sporadic periods of inactivity; the VI-dormant behavior, which was prevalent in the summer, involved long periods of inactivity with sporadic VI impacts. These data were used to study outcomes of three simple sparse data sampling plans; the probabilities of false-negative and false-positive decisions were dependent on the ratio of the (action level/true mean of the data), the number of exceedances needed, and the sampling strategy. The analysis also suggested a significant potential for poor characterization of long-term mean concentrations with sparse sampling plans. The results point to a need for additional dense data sets and further investigation into the robustness of possible VI assessment paradigms. As this is the first data set of its kind, it is unknown if the results are representative of other VI-sites.