Characterization of trace elements in PM_2.5 aerosols in the vicinity of highways in northeast New Jersey in the U.S. East coast

To characterize the spatial and temporal variations of atmospheric concentrations of trace elements in particulate matter with diameter less than 2.5 μm (PM_2.5) derived from vehicle emissions, aerosol sampling was conducted near the heavily trafficked New Jersey Turnpike (NJTPK) at East Rutherford, New Jersey in the U.S. east coast from September 2007 to September 2008. Aerosol samples were collected by Partisol-FRM Model 2000 air samplers at three sites within 150 m away from the NJTPK and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Concentrations of 13 trace elements (i.e., aluminum, cadmium, cobalt, chromium, copper, iron, lead, manganese, nickel, antimony, scandium, vanadium and zinc) varied as a function of distance away from NJTPK within 150 m. The concentrations of Al, Cd, Cr, Cu, Fe and Pb along the three sites decreased significantly away from the highway. In contrast, the concentrations of Mn, Sb, and Sc showed significantly positive correlations with distance. There were not clear concentration trends for Co, Ni, V and Zn with distance. Most trace elements showed slightly higher concentrations in spring and summer, except for Ni that was more enriched in the fall and winter. All measured trace elements showed higher concentrations on weekdays than on weekends, indicating high impact of traffic emissions on air pollution. In both summer and winter, most trace elements were enriched in daytime aerosols, and this trend was stronger in the winter. Meteorological conditions, mainly wind speed and wind direction, were found to affect the spatial and temporal concentration variations of trace elements in the ambient air at this location.