EFFECT OF PEROXY RADICAL REACTIONS ON THE PREDICTED CONCENTRATIONS OFOZONE, NITROGENOUS COMPOUNDS, AND RADICALS

The reactions of organic peroxy radicals with NO, HO2, organic peroxy radicals, and NO3 along with the formation and decomposition of peroxy acetyl nitrate are all important for the modeling of atmospheric chemi stry. Recent laboratory measurements of the rate constants for peroxy radical-peroxy radical reactions show that there are large differences between these rate constants. We present methods of estimating organi c peroxy radical self-reaction rate constants from an empirical expres sion. These self-reaction rate constants may be used to estimate the r ates of peroxy radical cross reactions. There are also new data availa ble on the rate constants for peroxyacetyl nitrate formation, decompos ition, the reaction of acetyl peroxy radicals and other organic peroxy radicals with NO, and the reactions of NO3 with organic peroxy radica ls. To estimate the importance of these reactions, these new data alon g with revisions to the product yields for organic peroxy radical-orga nic peroxy radical reactions were implemented in the mechanism of Stoc kwell et al. [1990]. The revised mechanism yields significantly differ ent concentrations of peroxyacetyl nitrate, higher organic hydroperoxi des and peroxyacetic acid concentrations. Nighttime concentrations of organic peroxy radicals, HO2, HO, and NO3 are also strongly affected b y organic peroxy radical-organic peroxy radical reactions and the reac tions of organic peroxy radicals with NO3. Our results suggest that th e reactions of organic peroxy radicals with NO3 are more important tha n organic peroxy radical-organic peroxy radical reactions in the night time atmosphere.