On the prediction of soil sorption coefficients of organic pollutants from molecular structure: application of molecular topology model

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This study was undertaken to test the ability of the molecular connectivity model to predict the soil sorption coefficients of polycyclic aromatic hydrocarbons (PAHs), alkylbenzenes, chlorobenzenes, chlorinated alkanes and alkenes, heterocyclic and substituted PAHs, and halogenated phenols. Tests performed on 31 such compounds clearly demonstrate that this simple nonempirical model accurately predicts the soil sorption coefficients for the above classes of compounds. Moreover, the model out performs the traditional empirical models based on 1-octanol/water partition coefficients or water solubilities in accuracy, speed, and range of applicability. Additional tests on approximately 160 polar and ionic compounds show that the above topological model plus a single semiempirical variable is capable of accounting for the soil sorption properties of nearly 95% of all organic chemicals whose soil sorption coefficients have been measured. The results of these tests demonstrate that the molecular connectivity model is a very accurate predictive tool for the soil sorption coefficients of a wide range of organic chemicals and that it can be confidently used to rank potentially hazardous chemicals and thus to create a priority testing list. 55 references, 5 figures, 7 tables.