title: Positive matrix factorization of PM2.5- eliminating the effects of gas/particle partitioning of semivolatile organic compounds.
abstract: Gas-phase concentrations of semi-volatile organic compounds (SVOCs) were calculated from gas/particle (G/P) partitioning theory using their measured particle-phase concentrations. The particle-phase data were obtained from an existing filter measurement campaign (27 January 2003-2 October 2005) as a part of the Denver Aerosol Sources and Health (DASH) study, including 970 observations of 71 SVOCs (Xie et al., 2013). In each compound class of SVOCs, the lighter species (e.g. docosane innalkanes, fluoranthene in PAHs) had higher total concentrations (gas + particle phase) and lower particle-phase fractions. The total SVOC concentrations were analyzed using positive matrix factorization (PMF). Then the results were compared with source apportionment results where only particle-phase SVOC concentrations were used (particle only-based study; Xie et al., 2013). For the particle only-based PMF analysis, the factors primarily associated with primary or secondary sources (nalkane, EC/sterane and inorganic ion factors) exhibit similar contribution time series (r= 0.92-0.98) with their corresponding factors (nalkane, sterane and nitrate+sulfate factors) in the current work. Three other factors (lightnalkane/PAH, PAH and summer/oddnalkane factors) are linked with pollution sources influenced by atmospheric processes (e.g. G/P partitioning, photochemical reaction), and were less correlated (r= 0.69-0.84) with their corresponding factors (light SVOC, PAH and bulk carbon factors) in the current work, suggesting that the source apportionment results derived from particle-only SVOC data could be affected by atmospheric processes. PMF analysis was also performed on three temperature-stratified subsets of the total SVOC data, representing ambient sampling during cold (daily average temperature < 10 °C), warm (≥ 10 °C and ≤ 20 °C) and hot (> 20 °C) periods. Unlike the particle only-based study, in this work the factor characterized by the low molecular weight (MW) compounds (light SVOC factor) exhibited strong correlations (r= 0.82-0.98) between the full data set and each sub-data set solution, indicating that the impacts of G/P partitioning on receptor-based source apportionment could be eliminated by using total SVOC concentrations.
authors.affiliation: Department of Mechanical Engineering, College of Engineering and Applied Science, University of Colorado, Boulder, CO 80309, USA.
authors.forename: M
authors.initials: M
authors.lastname: Xie
authors.affiliation: Department of Civil and Environmental Engineering, Portland State University, P.O. Box 751, Portland, OR 97207, USA.
authors.forename: K C
authors.initials: KC
authors.lastname: Barsanti
authors.affiliation: Department of Mechanical Engineering, College of Engineering and Applied Science, University of Colorado, Boulder, CO 80309, USA.
authors.forename: M P
authors.initials: MP
authors.lastname: Hannigan
authors.affiliation: National Center for Environmental Assessment, US Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Dutton
authors.affiliation: Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, Seattle, WA 98195, USA.
authors.forename: S
authors.initials: S
authors.lastname: Vedal