Tropospheric photochemical air pollution has impacts on scales ranging from local to global. The reactions of organic pollutants in the atmosphere with OH radicals, NO3 radicals, and ozone are of great concern from an ecological standpoint for risk assessment measurement such as degradation pathways, atmospheric lifetimes and fate of these compounds. It was already established that reactions with hydroxyl radical (-OH) is the most important pathway of day time removal of organic pollutant in atmosphere because of the reactive nature of OH radical to react practically almost with every volatile organic compounds (VOCs) in the troposphere. Due to limited availability of experimental gas phase rate constant data for chemicals, alternative theoretical approaches like QSAR/QSPRs are often practiced to predict the high risk of organic chemicals and to reduce the time consuming, expensive and difficult experimental procedures. In this study we developed QSAR models for hydroxyl radical tropospheric degradation rate of 460 VOCs, using HOMO, LUMO from Hyperchem minimization in addition to separately freely available online molecular descriptors (from the CADASTER online platform– www.cadaster.eu) or descriptors calculated from an updated version of DRAGON software. The Genetic Algorithm as Variable Subset Selection (GA-VSS) was used to select the relevant molecular descriptors in the modeling step (Ordinary Least Squares (OLS) regression). Three splitting criteria [K-ANN, k-means cluster and random on response] were applied for verifying the external predictivity of developed QSAR models, with special emphasis on model applicability domain which was verified by the leverage approach. The statistical qualities of the models developed from the pool of online descriptors were comparable with those obtained from the DRAGON descriptors and, most importantly, the GA selected, in addition to HOMO, descriptors with comparable mechanistic meaning, from completely different pool of input descriptors. So it can be suggested to use online freely available descriptors to increase the reproducibility of the models for the safety of environment and for REACH.

Exploring the QSARs for OH Tropospheric Degradation of VOCs using freely available online descriptors

PAPA, ESTER;GRAMATICA, PAOLA
2011-01-01

Abstract

Tropospheric photochemical air pollution has impacts on scales ranging from local to global. The reactions of organic pollutants in the atmosphere with OH radicals, NO3 radicals, and ozone are of great concern from an ecological standpoint for risk assessment measurement such as degradation pathways, atmospheric lifetimes and fate of these compounds. It was already established that reactions with hydroxyl radical (-OH) is the most important pathway of day time removal of organic pollutant in atmosphere because of the reactive nature of OH radical to react practically almost with every volatile organic compounds (VOCs) in the troposphere. Due to limited availability of experimental gas phase rate constant data for chemicals, alternative theoretical approaches like QSAR/QSPRs are often practiced to predict the high risk of organic chemicals and to reduce the time consuming, expensive and difficult experimental procedures. In this study we developed QSAR models for hydroxyl radical tropospheric degradation rate of 460 VOCs, using HOMO, LUMO from Hyperchem minimization in addition to separately freely available online molecular descriptors (from the CADASTER online platform– www.cadaster.eu) or descriptors calculated from an updated version of DRAGON software. The Genetic Algorithm as Variable Subset Selection (GA-VSS) was used to select the relevant molecular descriptors in the modeling step (Ordinary Least Squares (OLS) regression). Three splitting criteria [K-ANN, k-means cluster and random on response] were applied for verifying the external predictivity of developed QSAR models, with special emphasis on model applicability domain which was verified by the leverage approach. The statistical qualities of the models developed from the pool of online descriptors were comparable with those obtained from the DRAGON descriptors and, most importantly, the GA selected, in addition to HOMO, descriptors with comparable mechanistic meaning, from completely different pool of input descriptors. So it can be suggested to use online freely available descriptors to increase the reproducibility of the models for the safety of environment and for REACH.
2011
Roy, P. P.; Papa, Ester; Gramatica, Paola
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11383/1727783
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