A larger pool of ozone-forming carbon compounds in urban atmospheres

Volatile organic compounds play a central role in the processes that genera te both urban photochemical smog and tropospheric ozone(1,2). For successfu l and accurate prediction of these pollution episodes, identification of th e dominant reactive species within the volatile organic carbon pool is need ed(3). At present, lack of resolution inherent in single-column chromatogra phic analysis(4) limits such a detailed chemical characterization of the co mplex urban atmosphere. Here we present an improved method of peak deconvol ution from double-column (orthogonal) gas chromatography(5,6). This has ena bled us to isolate and classify more than 500 chemical species of volatile organic compounds in urban air, including over 100 multi-substituted monoar omatic and volatile oxygenated hydrocarbons. We suggest that previous asses sments of reactive carbon species may therefore have underestimated the con tribution made by volatile organic compounds to urban pollution, particular ly for compounds with more than six carbon atoms. Incorporating these speci es in predictive models should greatly improve our understanding of photoch emical ozone yields and the formation of harmful secondary organic aerosols (7,8).