Knowledge of the chemical pathways that determine the fate of atmospheric NOx remains incomplete, limiting our ability to accurately assess the impact of anthropogenic emissions on ecosystem health and climate. Nighttime processing of NOx is particularly uncertain. At night, NOx is oxidized to NO3 and N2O5. The latter reacts on aerosol particles, rendering a fraction to inert HNO3, while converting the rest to photo-labile nitryl chloride (ClNO2) which yields chlorine atoms and NOx upon sunrise. Nitrate radicals (NO3) react with volatile organic compounds (VOCs) � primarily of biogenic origin � to form multifunctional alkyl nitrates, the fate of which have implications for regional ozone production and SOA formation. The efficiencies and yields of these homogeneous and heterogeneous processes remain highly uncertain. We use aircraft and ground-based observations from two recent field campaigns in the Southeast U.S. together with results from laboratory studies using entrained aerosol flow reactors and steady-state chambers to evaluate the importance of nocturnal NO3 driven formation of some never before reported isoprene and monoterpene nitrates in gas and particle phaes, the reaction efficiency of N2O5 on mixed organic-inorganic aerosol particles, and the activation of chlorine in power plant plumes.

Homogenous and heterogeneous chemistry of nocturnal nitrogen oxides in high biogenic VOC environments: Implications for NO<sub>x</sub> removal, halogen activation, and SOA formation

248th National Meeting (2014)

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Homogenous and heterogeneous chemistry of nocturnal nitrogen oxides in high biogenic VOC environments: Implications for NOx removal, halogen activation, and SOA formation

Homogenous and heterogeneous chemistry of nocturnal nitrogen oxides in high biogenic VOC environments: Implications for NO_x removal, halogen activation, and SOA formation