Dechlorination pathways of diverse chlorinated aromatic pollutants conducted by Dehalococcoides sp. strain CBDB1 Original Research Article

Dechlorination of chlorinated aromatic pollutants (CAPs) has become a major issue in recent decades. This paper reported a theoretical indicator for predicting the reductive dechlorination pathways of polychlorinated dibenzo-p-dioxins (PCDDs), chlorobenzenes and chlorophenols transformed by Dehalococcoides sp. strain CBDB1. Density functional theory (DFT) calculations were carried out at the B3LYP/6-31G(d) level for all related CAPs and Mulliken atomic charges on chlorine atoms (QCl(n)) were adopted as the probe of the dechlorination reaction activity. QCl(n) can consistently indicate the main dechlorination daughter products of PCDDs, chlorobenzenes and chlorophenols conducted by strain CBDB1. The dechlorination reaction favors elimination of the chlorine atoms having greater QCl(n) values. The chlorine atom with the greatest QCl(n) value tends preferentially to be eliminated, whereas the chlorine atom with the smallest QCl(n) value tends unlikely to be eliminated or does not react at all. For a series of compounds having similar structure, the maximal QCl(n) of each molecular can be used to predict the possibility of its daughter product(s). In addition, the difference (∆QCl(n)) between the maximal QCl(n) and the next maximal QCl(n) of the same molecule can be used to assess the possibility of formation of multiple dechlorination products.