Spatial and seasonal distribution of aerosol chemical components in New York City: (2) Road dust and other tracers of traffic-generated air pollution

We describe spatial and temporal patterns of seven chemical elements commonly observed in fine particulate matter (PM) and thought to be linked to roadway emissions that were measured at residential locations in New York City (NYC). These elements, that is, Si, Al, Ti, Fe, Ba, Br, and black carbon (BC), were found to have significant spatial and temporal variability at our 10 residential PM _2.5 sampling locations. We also describe pilot study data of near-roadway samples of both PM _10-2.5 and PM _2.5 chemical elements of roadway emissions. PM _2.5 element concentrations collected on the George Washington Bridge (GWB) connecting NYC and New Jersey were higher that similar elemental concentration measured at residential locations. Coarse-particle elements (within PM _10-2.5) on the GWB were 10-100 times higher in concentration than their PM _2.5 counterparts. Roadway elements were well correlated with one another in both the PM _2.5 and PM _10-2.5 fractions, suggesting common sources. The same elements in the PM _2.5 collected at residential locations were less correlated, suggesting either different sources or different processing mechanisms for each element. Despite the fact that these elements are only a fraction of total PM _2.5 or PM _10-2.5 mass, the results have important implications for near-roadway exposures where elements with known causal links to health effects are shown to be at elevated concentrations in both the PM _2.5 and PM _10-2.5 size ranges.