Peroxyacetyl nitrate in Atlanta, Georgia: Comparison and analysis of ambient data for suburban and downtown locations

Peroxyacetyl nitrate (PAN) concentrations were measured at downtown and suburban locations in Atlanta, GA, in July and August 1992 as part of the SOS-SORP/ONA (Southern Oxidants Study-Southern Oxidants Research Program on Ozone Non-Attainment). PAN concentrations were generally higher at the downtown location than at the suburban location, but on days when the O-3 concentration exceeded 80 ppbv, PAN concentrations were similar at both locations. On days when O-3 did not exceed 80 ppbv, suburban PAN concentrations were much lower than downtown concentrations and resembled those reported for rural areas in the eastern United States. Regression analysis of PAN and O-3 on NOx and total non-methane hydrocarbons (TNMHC) showed PAN to be most strongly dependent on morning NOx concentrations, while O-3 was most dependent on morning TNMHC concentrations. NOx, PAN, and meteorological data from the suburban site were used in a one-dimensional transport model to estimate the accumulation rate of PAN to be similar to 1.5 x 10(6) molecules cm(-3) sec(-1). A simple kinetic model estimated peroxyacetyl radical concentrations to be similar to 0.5 pptv at the suburban location.