Seasonal Gradient Patterns of Polycyclic Aromatic Hydrocarbons and Particulate Matter Concentrations near a Highway

Close proximity to roadways has been associated with higher exposure to traffic-related air pollutants. However, analyses of the effects of season and meteorological parameters on horizontal gradient patterns of traffic-generated air pollutants still need to be elucidated. Our objectives were to: (1) determine effects of season on horizontal gradient patterns of polycyclic aromatic hydrocarbons (PAHs), total suspended particles (TSP), and PM2.5 near a heavily trafficked highway; and (2) examine the effect of day-of-the-week variations (weekday versus weekend) associated with traffic counts on measured airborne-contaminant levels. PAHs (Sigma(PAHs)(8) [MW 228-278]; gas + particulate), TSP and PM2.5 were monitored at nominal distances (50, 100, and 150 m) from the New Jersey Turnpike every 6 days for periods of 24 h, between September 2007 and September 2008. Seasonal variations in the horizontal gradient patterns of Sigma(PAHs)(8) were observed. In the summer, Sigma(PAHs)(8) declined significantly between 50-100 m from the highway (23% decrease), but not between the furthermost distances (100-150 m). An inverse pattern was observed in the winter: Sigma(PAHs)(8) declined between 100-150 m (26% decrease), but not between the closest distances. Sigma(PAHs)(8) and TSP, but not PM2.5, concentrations measured on weekends were 12-37% lower than those on weekdays, respectively, corresponding to lower diesel traffic volume. This study suggests that people living in the close proximity to highways may be exposed to varying levels of Sigma(PAHs)(8), TSP, and PM2.5 depending on distance to highway, season, and day-of-the-week variations.