Dynamics of Particle- and Gas-Phase Total Water-Soluble Organic Carbon at the CASA Indoor Air Study

MARC WEBB, Glenn Morrison, Naomi Chang, Karsten Baumann, Marina Vance, Delphine K. Farmer, Dustin Poppendieck, Barbara Turpin, University of North Carolina at Chapel Hill

     Abstract Number: 367
     Working Group: Indoor Aerosols

Abstract
Previous time-integrated (2-4 hour) measurements have demonstrated that total gas phase water soluble organic carbon (WSOCg) is 10-20 times higher inside homes compared to outside. However, the sources, sinks, reservoirs, and dynamics of gas phase (WSOCg) and particle phase WSOC (WSOCp) in indoor air are not well understood, and to our knowledge, WSOC species mass closure has not been attempted. As part of the recent CASA indoor air study, a total carbon analyzer alternated every 6 min between a particle-into-liquid sampler (PILS) and mist chamber (MCs) to capture the real-time (4 s resolution) dynamics of WSOCg and WSOCp in the unfurnished, unoccupied National Institute of Standards and Technology Net Zero Energy Test House during a variety of scripted activities. The low WSOC background with windows open and high WSOC background with windows closed suggests that building materials comprise a major source of WSOC. WSOCg was generally 3-4x higher than WSOCp. Scripted indoor cooking and cleaning (except for cooking with vinegar) were minor contributors, whereas the introduction of smog precursors (acetone, toluene-d8, o-xylene, chlorobenzene, 2-pentanone, 2-heptanone, alpha-Pinene, 1-hexene, isoprene, 1-octene, furfural) and simulated wildfire smoke significantly increased indoor WSOC concentrations. Surprisingly, ozone additions did not induce a measurable increase in WSOC. WSOCg and WSOCp decay rates were 0.90 and 0.94 hr-1, respectively, with window opening; when windows were subsequently closed concentrations rebounded, presumably as a result of WSOC release from indoor reservoirs. The effects of activities, indoor conditions, ventilation and air cleaners and insights concerning indoor WSOC reservoirs will be discussed.