A METHODOLOGY FOR MODELING THE FORMATION AND DECAY OF NITRO-PAH IN THE ATMOSPHERE

An outdoor chamber system with dilute diesel exhaust was used to photochemically generate nitrolycyclic aromatic hydrocarbons (NPAH). A reaction scheme was proposed for PAH decay and NPAH formation and decay. These reactions were then added to the photochemical smog mechanism, Carbon Bond-4. The primary ps phase reactions for fluoranthene (FL) and pyrene (PY) involved hydroxyl radical (OH) attack. The addition of NO2 to the ps phase adduct of FL + OH or PY + OH was the only pathway for 2NF and 2NP formation in model simulations. Simulations of the formation and decay of 2-nitrofluoranthene (2NF) and the photo-decay of 1&2 nitropyrene were reasonably close to measured chamber concentrations. The greatest uncertainties in the current model were the rates (or yields) from NO2 addition to the OH-PAH adducts to form NPYs and NFLs, and the photo-induced decay rates of particle associated 2NP and 2NF. Of additional importance is the potential reaction of O3 with particle NPAH, and the possibility of unknown particle reactions leading to NPAH formation.