Ubiquitous occurrence of 2-nitrofluoranthene and 2-nitropyrene in air

Abstract

Several nitrated polycyclic aromatic hydrocarbons (nitro-PAH) are direct-acting mutagens^1,2 and/or carcinogens^2–4, and are important constituents of combustion emissions and ambient air. These nitro-PAH are emitted from various combustion sources including gasoline and diesel engine exhaust^5–8, aluminium smelting effluent⁹, coal fly ash¹⁰, wood smoke⁶, and cigarette smoke condensates¹¹. Of these, diesel engine exhaust is the best characterized^6–8, more than 50 nitrated polycyclic aromatic compounds having been identified by Paputa-Peck et al.⁸, including 1-nitropyrene (1-NP) as the single most abundant nitro-PAH. However, nitro-PAH may also be formed during source–receptor transport by atmospheric reactions of adsorbed or gas-phase PAH with oxides of nitrogen, nitric acid and other atmospherically important species such as the OH radical^1,12–14. Evidence for the atmospheric formation of nitro-PAH has come only recently, from observations that 2-nitropyrene (2-NP)^15–17 and 2-nitrofluoranthene (2-NF)^16,17 neither of which has been reported to be emitted from combustion sources, are among the major nitro-PAH present in ambient air. We present here data from several locations which demonstrate that these two atmospherically formed nitro-PAH are ubiquitous in tropospheric ambient air.