Evaluation Of Operator Approaches For PeroxyRadical - Peroxy Radical Reactions

Abstract

Peroxy radical peroxy radical reactions are important because these reactions affect peroxyacetyl nitrate concentrations (PAN), the atmospheric nitrogen balance and they are the dominant sink for peroxy radicals when nitric oxide concentrations are low. Many chemical mechanisms for photochemical air pollution models use operator approaches to represent peroxy radical peroxy radical reactions. The operator approach assumes that all peroxy radical reactions have the same rate constants or at least that the reactions can be characterized by only a very few rate constants. Our analysis of recent laboratory measurement data shows that there is a large variation in the rate constants for peroxy radical reactions that is not adequately described by the operator schemes. We present comparisons of the rate constants used by the simple operator approaches with measured values and those estimated from more complex parameterizations. We show that the simple operator approaches to peroxy radical peroxy radical reactions used in current models are not valid for many peroxy radical reactions.