Modeling the formation, decay, and partitioning of semivolatile nitro-polycyclic aromatic hydrocarbons (nitronaphthalenes) in the atmosphere

A nitronaphthalene kinetics mechanism has been implemented and added to the photochemical smog mechanism, Carbon Bond-4. This mechanism was used to si mulate the formation, decay, and partitioning of 1- and 2-nitronaphthalene and compare it to outdoor smog chamber data. The results suggest that these types of mechanisms can be used to model nitronaphthalene formation and de cay in regional airmasses. The partitioning experiments were conducted at n ight. The sampling system consisted of two Teflon impregnated glass fiber f ilters followed by a gas-phase denuder. Evidence is provided that partition ing equilibrium is maintained even when the gas-phase components are decayi ng rapidly under sunlight. The photolysis rate constants were determined re lative to k(NO2) to be 0.07 x k(NO2) and 0.005 x k(NO2) for 1- and 2-nitron aphthalene, respectively. Our results confirm that gas-phase photolysis is the major degradation pathway for 1-nitronaphthalene, whereas for 2-nitrona phthalene other pathways may also be important. The photochemical formation of nitronaphthalenes was studied using a mixture of naphthalene, propylene , NOx, and diesel particles. 2-nitronaphthalene was observed to build up to higher levels than 1-nitronaphthalene, as the photodegradation of the latt er was faster. Additionally, as a part of this study 1-nitronaphthalene has been identified and quantified in diesel exhaust. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.