Photochemical Formation of Hydroxylated Polybrominated Diphenyl Ethers (OH-PBDEs) from Polybrominated Diphenyl Ethers (PBDEs) in Aqueous Solution under Simulated Solar Light Irradiation

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) are of great concern due to their higher toxicity compared to PBDEs. However, the abiologic process whereby PBDEs are converted to OH-PBDEs in the aquatic environment is not well understood. To explore the possibility of OH-PBDEs photoformation in natural water, the photohydroxylation of BDE-47 has been investigated in aqueous Fe­(III) and/or fulvic acid (FA) solutions and in natural lake water under simulated solar light irradiation. The results showed that 6-OH-BDE-47 and 2′-OH-BDE-68 were generated from BDE-47 under these conditions. Based on the identification of derivatives and reactive radicals, OH-PBDEs formation can be ascribed to an addition reaction of <i>ortho</i>-tetra-BDE radical and hydroxyl radical (^•OH), with or without a subsequent Smiles rearrangement reaction. Since the <i>ortho</i>-tetra-BDE radical could be readily produced by the photolysis of BDE-47, even in pure water, ^•OH production was considered as critical for the photoformation of OH-PBDEs. Thus, it is reasonable to deduce that the photoreactive components (Fe­(III), FA) in aqueous solution played an important role through influencing ^•OH generation. Although the yields of OH-PBDEs did not increase regularly with increasing concentration of these photoreactive components in solution, this study suggests a possible abiotic origin of OH-PBDEs formation in the aquatic environment