Estimation of microbial reductive transformation rates for chlorinated benzenes and phenols using a quantitative...

A set of literature data was used to derive several quantitative structure-activity relationships (QSARs) to predict the rate constants for the microbial reductive dehalogenation of chlorinated aromatics. Dechlorination rate constants for 25 chloroaromatics were corrected for the effects of hydrophobic partitioning and adjusted for the observed distribution of product species. A number of physicochemical properties and molecular parameters were considered for inclusion in the QSARs. Multivariate statistical analyses were used to select the optimal set of descriptors to minimize multicollinearity between the descriptors, as well as to minimize the p-value of the regression coefficients. The final QSAR included four descriptors: The logarithm of the octanol-water partition coefficient (Kow), the summation of the Hammett sigma constants, and the sigma induction constants in the ortho and meta positions relative to the transformation reaction center. The predictive ability of this QSAR was evaluated using 24 site-specific rate constants that were measured in five separate studies and were not used to derive the expression. The peer-reviewed literature was screened carefully to ensure that all rate constant data were representative of environmentally relevant conditions.