Identification of Structural Properties Associated with Polychlorinated Biphenyl Dechlorination Processes

摘要

Polychlorinated biphenyl molecules can be biologically dechlorinated through sequential losses of a chlorine atom, following 840 pathways from higher chlorinated to lesser-chlorinated congeners and biphenyl. Previously, eight recurring sets of pathways, herein referred to as explicitly reported pathways in dechlorination processes, have been identified through qualitative analysis of shifts in congener masses in field and laboratory studies. Dechlorination process generalizations were qualitatively extrapolated based on limited attributes of the congeners dechlorinated in the explicitly reported pathways. They are valuable because they allow comparisons of dechlorination patterns across laboratory experiments and contaminated sites. However, due to analytical limitations and a paucity of studies, the explicitly reported pathways in dechlorination processes likely do not represent all of the pathways that could occur at contaminated sites. This work presents an alternative, quantitative, and replicable approach to the identification of candidate pathways for inclusion in dechlorination process generalizations through use of classification trees. This method considers 46 structural and property attributes of dechlorination pathways. Trees fit for pathway inclusion in each of the eight dechlorination processes with alternative assumptions are compared in terms of critical congener attributes. The classification trees correctly classify explicitly reported pathways into dechlorination processes at rates of 0.90 to 0.99. While many of the attributes used in the original generalizations were also selected as predictors by the classification trees, the extra attributes allow identification of additional dechlorination pathways that can be considered as candidates for monitoring in future studies.