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A FUNCTIONAL GROUP CHARACTERIZATION OF ORGANIC PM 2.5 EXPOSURE: RESULTS FROM THE RIOPA STUDY
Citation:
REFF, A. H., B. TURPIN, J. H. OFFENBERG, C. P. WEISEL, J. ZHANG, M. T. MORANDI, T. STOCK, S. COLOME, AND A. M. WINER. A FUNCTIONAL GROUP CHARACTERIZATION OF ORGANIC PM 2.5 EXPOSURE: RESULTS FROM THE RIOPA STUDY. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 41(22):4585-4598, (2007).
Impact/Purpose:
The objectives of this task are to continue development and improvement of EPA's mesoscale (regional through urban scale) air quality modeling systems, such as the Community Multiscale Air Quality (CMAQ) model, as air quality management and NAAQS implementation tools. This task focuses on needed research and development of air quality models targeted for a major CMAQ model release in FY08. Model development for a broad scope of application is envisioned. For example, CMAQ will need to be able to simulate air quality feedbacks to meteorology and climate as well as intercontinental transport. The 2008 release of CMAQ is timed to coincide with EPA/OAR's and the states' needs for an improved model for assessments of progress (mid-course corrections) in the post-SIP submittal timeframe.
Description:
The functional group (FG) composition of urban residential outdoor, indoor, and personal fine particle (PM2.5) samples is presented and used to provide insights relevant to organic PM2.5 exposure. PM2.5 samples (48 h) were collected during the Relationship of Indoor, Outdoor, and Personal Air (RIOPA) study at 219 non-smoking homes (once or twice) in Los Angeles County, CA, Elizabeth, NJ, and Houston, TX. Fourier transform infrared (FTIR) spectra of PM2.5 samples were collected, and FG absorbances were quantified by partial least squares (PLS) regression, a multivariate calibration method. There is growing evidence in the literature that a large majority of indoor-generated PM2.5 is organic. The current research suggests that indoor-generated PM2.5 is enriched in aliphatic carbon-hydrogen (CH) FGs relative to ambient outdoor PM2.5. Indoor-generated CH exceeded outdoor-generated CH in 144 of the 167 homes for which indoor or outdoor CH was measurable; estimated indoor emission rates are provided. The strong presence of aliphatic CH FGs in indoor PM2.5makes particulate organic matter substantially less polar indoors and in personal exposures than outdoors. This is a substantial new finding. Based on the quantified functional groups, the average organic molecular weight (OM) per carbon weight (OC), a measure of the degree of oxygenation of organic PM, is in the range of 1.7-2.6 for outdoor samples and 1.3-1.7 for indoor and personal samples. Polarity or degree of oxygenation effects particle deposition in exposure environments and in the respiratory system.