TitleFormation of nitro-PAHs from the heterogeneous reaction of ambient particle-bound PAHs with N2O5/NO3/NO2.
Publication TypeJournal Article
Year of Publication2013
AuthorsZimmermann, K, Jariyasopit, N, Simonich, SLMassey, Tao, S, Atkinson, R, Arey, J
JournalEnviron Sci Technol
Volume47
Issue15
Pagination8434-42
Date Published2013 Aug 6
ISSN1520-5851
KeywordsAdsorption, Nitrogen Oxides, Particulate Matter, Polycyclic Hydrocarbons, Aromatic, Surface Properties
Abstract

Reactions of ambient particles collected from four sites within the Los Angeles, CA air basin and Beijing, China with a mixture of N2O5, NO2, and NO3 radicals were studied in an environmental chamber at ambient pressure and temperature. Exposures in the chamber system resulted in the degradation of particle-bound PAHs and formation of molecular weight (mw) 247 nitropyrenes (NPYs) and nitrofluoranthenes (NFLs), mw 273 nitrotriphenylenes (NTPs), nitrobenz[a]anthracenes (NBaAs), nitrochrysene (NCHR), and mw 297 nitrobenzo[a]pyrene (NBaP). The distinct isomer distributions resulting from exposure of filter-adsorbed deuterated fluoranthene to N2O5/NO3/NO2 and that collected from the chamber gas-phase suggest that formation of NFLs in ambient particles did not occur by NO3 radical-initiated reaction but from reaction of N2O5, presumably subsequent to its surface adsorption. Accordingly, isomers known to result from gas-phase radical-initiated reactions of parent PAHs, such as 2-NFL and 2- and 4-NPY, were not enhanced from the exposure of ambient particulate matter to N2O5/NO3/NO2. The reactivity of ambient particles toward nitration by N2O5/NO3/NO2, defined by relative 1-NPY formation, varied significantly, with the relative amounts of freshly emitted particles versus aged particles (particles that had undergone atmospheric chemical processing) affecting the reactivity of particle-bound PAHs toward heterogeneous nitration. Analyses of unexposed ambient samples suggested that, in nighttime samples where NO3 radical-initiated chemistry had occurred, heterogeneous formation of 1-NPY on ambient particles may have contributed to the ambient 1-NPY concentrations at downwind receptor sites. These results, together with observations that 2-NFL is consistently the dominant particle-bound nitro-PAH measured in ambient atmospheres, suggest that for PAHs that exist in both the gas- and particle-phase, the heterogeneous formation of particle-bound nitro-PAHs is a minor formation route compared to gas-phase formation.

DOI10.1021/es401789x
Alternate JournalEnviron. Sci. Technol.
PubMed ID23865889
PubMed Central IDPMC4167764
Grant ListP30 ES000210 / ES / NIEHS NIH HHS / United States
P30ES00210 / ES / NIEHS NIH HHS / United States
P42 ES016465 / ES / NIEHS NIH HHS / United States
P42 ES016465 / ES / NIEHS NIH HHS / United States