Organic compound characterization and source apportionment of indoor and outdoor quasi-ultrafine particulate matter in retirement homes of the Los Angeles Basin

Abstract

Quasi-ultrafine (quasi-UF) particulate matter (PM(0.25)) and its components were measured in indoor and outdoor environments at four retirement communities in Los Angeles Basin, California, as part of the Cardiovascular Health and Air Pollution Study (CHAPS). The present paper focuses on the characterization of the sources, organic constituents and indoor and outdoor relationships of quasi-UF PM. The average indoor/outdoor ratios of most of the measured polycyclic aromatic hydrocarbons (PAHs), hopanes, and steranes were close to or slightly lower than 1, and the corresponding indoor-outdoor correlation coefficients (R) were always positive and, for the most part, moderately strong (median R was 0.60 for PAHs and 0.74 for hopanes and steranes). This may reflect the possible impact of outdoor sources on indoor PAHs, hopanes, and steranes. Conversely, indoor n-alkanes and n-alkanoic acids were likely to be influenced by indoor sources. A chemical mass balance model was applied to both indoor and outdoor speciated chemical measurements of quasi-UF PM. Among all apportioned sources of both indoor and outdoor particles, vehicular emissions was the one contributing the most to the PM(0.25) mass concentration measured at all sites (24-47% on average).

Practical implications: Although people (particularly the elderly retirees of our study) generally spend most of their time indoors, a major portion of the PM(0.25) particles they are exposed to comes from outdoor mobile sources. This is important because, an earlier investigation, also conducted within the Cardiovascular Health and Air Pollution Study (CHAPS), showed that indoor-infiltrated particles from mobile sources are more strongly correlated with adverse health effects observed in the elderly subjects living in the studied retirement communities compared with other particles found indoors (Delfino et al., 2008).

Figure 1

Outdoor concentrations of a) PAH’s, b) Hopanes and Steranes, c) n-Alkanes and d) Acids. The presented values are average concentrations across all sites and error bars are standard deviation of these averages at each site.

Figure 1

Outdoor concentrations of a) PAH’s, b) Hopanes and Steranes, c) n-Alkanes and d) Acids. The presented values are average concentrations across all sites and error bars are standard deviation of these averages at each site.

Figure 2

Concentration of total a) PAH’s, b) Hopanes and Steranes, c) n-Alkanes and d) Acids. Dots are average of concentrations across all the sites and error bars are standard deviation of these averages at each site

Figure 2

Concentration of total a) PAH’s, b) Hopanes and Steranes, c) n-Alkanes and d) Acids. Dots are average of concentrations across all the sites and error bars are standard deviation of these averages at each site

Figure 3

Correlation coefficient and indoor and outdoor ratios of a) PAHs, b) Hopanes and Steranes, c) n-Alkanes and d) Acids, values are averaged over the sites and bars are the standard deviation over the sites

Figure 3

Correlation coefficient and indoor and outdoor ratios of a) PAHs, b) Hopanes and Steranes, c) n-Alkanes and d) Acids, values are averaged over the sites and bars are the standard deviation over the sites

Figure 4

Coefficient of variance (CV) for indoor and outdoor organic groups for: a) warmer and b) colder period of the study

Figure 5

Contribution of different sources to quasi-ultrafine PM in the four sites and during the two sampling periods