MODELING STUDIES OF NO3 NIGHTTIME CHEMISTRY AND ITS EFFECTS ON SUBSEQUENT OZONE FORMATION

A photochemical box model (NITE-UP) supplied with an updated and addit ional daytime and nighttime chemical scheme, has been applied to night time emissions from a major city (London). Studies have been made of t he importance of the temperature-dependent rate constant of the homoge neous and heterogeneous reactionN2O5 + H2O --> 2HNO(3) on NO3 radicals production. The involvement of the nitrate radical in the nighttime t ropospheric chemistry and its influences on the concentrations of othe r species including N2O5, HNO3, OH, HO2, as well as on the subsequent ozone formation have been modelled for the area downwind of London, un der summertime and springtime conditions. The significance of the repr esentation of the NO3 chemistry in computational photochemical models is discussed. (C) 1997 Elsevier Science Ltd.