Determining source impacts near roadways using wind regression and organic source markers

Concentrations of 13 organic source markers (10 polycyclic aromatic hydrocarbons and 3 hopanes) are reported from time-integrated samples (24-h and sub-daily) collected near a highway in Las Vegas, NV. Sample selection for assessing source impacts from the roadway was completed using the wind regression model Air Pollution Transport to Receptor model (EPA APTR 1.0). The model uses a kernel smoothing method for estimating source sectors (sector apportionment) of chemicals across wind speeds and wind directions. The model was applied using semi-continuous (5-min averaging time) pollutant data (black carbon (BC), CO, NO2, and NOx) and meteorological data. Using simple screening criteria to identify source impacts (>30% sector apportionment from the roadway and errors in the estimated sector apportionment <30%), sector apportionment results were consistent with organic source marker concentrations representative of motor vehicle exhaust (e.g., benzo(g,h,i)perylene and hopane). Results demonstrated the use of APTR to identify source-impacted time intervals when compared with filter samples analyzed for organic source markers.