Effect of Cu on the Laccase-Inducted Formation of Non-Extractable Residues of Tetrabromobisphenol A in Humic Acids.

We used  C-radiolabelling to study the non-extractable residues (NERs) formation of tetrabromobisphenol A (TBBPA) in a humic acid (HA) suspension under catalysis of laccase in the presence of copper. When entering the suspension after TBBPA adsorbing to HA supramolecular associates, Cu at low concentrations (even without toxicity to laccase) significantly reduced the amount and first-order kinetic constant of the NER formation, while Cu had no significant effect on the formation after it was complexed with HA. The inhibition effect of Cu on the NER formation is explained to be attributed to the prevention of laccase-induced oxidation of TBBPA in the voids of HA associates by complexation of Cu with periphery molecules of the associates. The results provide insights into varying effects of heavy metals on the environmental fate of organic contaminants and suggest that co-existing heavy metals could increase their environmental risk by reducing their NER formation.