Predicting the abiotic degradability of organic pollutants in the troposphere

Based on a global average of the OH and NO3 free radial concentration in th e troposphere, the lifetime of organic chemicals can be calculated from the rate constant of their reaction with the free radicals. Various models for estimating the reactivity of organic compounds with the tropospheric free radicals allow a rapid estimation of their degradability. An overview on th e existing models - empirical, quantitative structure-activity relationship s (QSAR) with measured physico-chemical descriptors, QSAR with semiempirica l quantum-chemical descriptors as well as ab initio molecular orbital calcu lations - is described and their limitations and range of applicability to estimate the tropospheric lifetime of an organic compound is discussed.