A tool for the assessment of VOC degradability by tropospheric oxidants starting from chemical structure

The tropospheric lifetime of most organic chemicals deriving from terrestrial emissions is mainly controlled by their degradation reaction with OH radicals and ozone during the daytime, and NO3 radicals at night. The studied data set, composed of 399 structurally heterogeneous volatile organic compounds (VOCs), consists of data for the three studied oxidation reactions, available either experimentally or from our herein reported quantitative structure–activity relationships (QSAR) models. A principal component analysis (PCA) model based on these principal oxidative degradations has been proposed to evaluate the overall tropospheric degradability of chemicals. The score of the first principal component can be proposed as an ATmospheric Degradability INdex (ATDIN) and is modelled by theoretical molecular descriptors to obtain a multiple linear regression (MLR) QSAR model with high predictive power, both internally and externally validated. This modelling approach allows a fast and preliminary VOC ranking according to their tendency to be degraded by atmospheric oxidants, starting only from the knowledge of their molecular structure.