LAND USE PATTERNS AND SIZE-RESOLVED POLYCYCLIC AROMATIC HYDROCARBONS IN AN URBAN AIR

People living in urban areas constantly inhale particulate matter (PM), a mixture of natural and anthropogenic pollutants, in the air. While the health effects of fine and coarse PM are well understood, the health effects of exposure to ambient levels of ultrafine particles (UFPs) are much less understood in urban populations. An important reason for this gap in knowledge regarding increased health risks associated with exposure to UFPs is the lack of geo spatial measurement in urban areas. Ambient air levels of fine PM are available from the national air monitoring stations across the United States. However, measurement of ambient UFP can be only evaluated by investigators directly conducting community-level air sampling. The main objective of the study was to characterize spatial and temporal variation of ambient air levels (mass) of polycyclic aromatic hydrocarbons (PAHs) in 5 different size modes including coarse, fine, and quasi-UFP (particle size less than 0.25 micro-meter) in Houston, TX. With no zoning in the city of Houston, myriad industries are often in close proximity to neighboring communities and this likely contributes to differences in ambient air quality in neighborhoods throughout the city. Filter-based size-resolved ambient PM was concurrently collected at five monitoring sites between October 2012 and May 2013. The measurements included 15 weekly integrated particle mass and PAHs. Preliminary results showed that average concentrations of sum of 16 PAHs designated by US EPA were 2.86 ng/m3 for quasi-UFPs followed by PM0.5 (2.05 ng/m3), PM1 (1.63 ng/m3), and PM2.5 (0.85 ng/m3). Correlations among the sites were moderate to high for spatial distributions in mass, PAHs in all four size fractions. However, higher spatial variability was observed in the quasi-UFP (smallest particle size fractions), suggesting the effect of local sources and PM emissions by different land use types.