Airborne observations of total RONO 2 : new constraints on the yield and lifetime of isoprene nitrates, Atmos. Abstract. Formation of isoprene nitrates (INs) is an important free radical chain termination step ending production of ozone and possibly affecting formation of secondary organic aerosol. Isoprene nitrates also represent a potentially large, unmeasured contribution to OH reactivity and are a major pathway for the removal of nitrogen oxides from the atmosphere. Current assessments

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... ate that formation rates of isoprene nitrates are uncertain to a factor of 2-3 and the subsequent fate of isoprene nitrates remains largely unconstrained by laboratory, field or modeling studies. Measurements of total alkyl and multifunctional nitrates ( ANs), NO 2 , total peroxy nitrates ( PNs), HNO 3 , CH 2 O, isoprene and other VOC were obtained from the NASA DC-8 aircraft during summer 2004 over the continental US during the INTEX-NA campaign. These observations represent the first characterization of ANs over a wide range of land surface types and in the lower free troposphere. ANs were a significant, 12-20%, fraction of NO y throughout the experimental domain and ANs were more abundant when isoprene was high. We use the observed hydrocarbon species to calculate the relative contributions of AN precursors to their produc-