Effects of the FeII/CuII Interaction on Copper Aging Enhancement and Pentachlorophenol Reductive Transformation in Paddy Soil

The present study investigated copper aging and pentachlorophenol (PCP) reductive transformation under the effects of the Fe-II/Cu-II interaction in paddy soil in south China. Kinetic measurements demonstrated that the PCP reductive transformation rate (k) could be promoted in the presence of no more than 0.375 mM Cu-II and inhibited in the presence of no less than 0.5 mM Cu-II. The highest k value in the presence of 0.25 mM Cu-II corresponds to the lowest redox potential (E-p) value of active Fe species. The increasing trend in E-p of the active Fe species is consistent with the declining trend in the k value of PCP reduction and vice versa. Dissolved Cu-II is gradually transformed into immobilized Cu species during PCP reduction, which indicates that Cu aging is enhanced by the Fe-II/Cu-II interaction. These findings improve our general understanding of the Fe-II/Cu-II interaction on soil iron redox chemistry for polychlorinated pesticide detoxification and heavy metal immobilization.