Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, PR China.
Chemosphere. 2013 Jan;90(2):188-94. doi: 10.1016/j.chemosphere.2012.06.033. Epub 2012 Jul 23.
Hydroxylated polybrominated diphenyl ethers (HO-PBDEs) pose potential ecological risks due to their endocrine disrupting effects and extensive sources. It is of great importance to know their environmental transformation for the purpose of ecological risk assessment. Photodegradation is an important transformation pathway of HO-PBDEs. As HO-PBDEs ionize in natural waters, the photochemical reactivities of both neutral and anionic HO-PBDEs need to be unveiled. In this study, six HO-PBDEs were selected as model compounds. Their direct photolysis rate constants (k(d)), quantum yields (Φ), light absorptions (A), second-order reaction rate constants with (1)O(2) (k(1O2)) and (·)OH (k(OH)) at different pH were determined, as well as these parameters for the neutral and anionic HO-PBDEs. The k(d), Φ, A, k(1O2) and k(OH) for the anions are much higher than those for the neutral molecules and vary with the bromination degree. Molecular parameters computed with the density functional theory (DFT) were employed to construct structure-reactivity equations. The ether bond strength, the frontier molecular orbital energy and the charge distribution were found to be the intrinsic structural characters governing the photochemical reactivities. The half-lives range from 0.7 to 60.1h for the photodegradation including the direct photolysis and the reactions with (1)O(2) and ()OH in surface waters at 45°N latitude under the continuous solar irradiation of sunny noon on 15 July. Direct photolysis is the dominant pathway. The photochemical reactivities of other HO-PBDEs at a given pH can also be estimated based on the structure-reactivity equations, which is important for the ecological risk assessment of HO-PBDEs.
羟基化多溴二苯醚（HO-PBDEs）由于其内分泌干扰效应和广泛的来源而构成潜在的生态风险。了解其环境转化对于生态风险评估至关重要。光降解是 HO-PBDEs 的重要转化途径。由于 HO-PBDEs 在天然水中发生电离，因此需要揭示中性和阴离子 HO-PBDEs 的光化学反应活性。在本研究中，选择了六种 HO-PBDEs 作为模型化合物。测定了它们的直接光解速率常数（k(d)）、量子产率（Φ）、光吸收（A）、与（1）O（2）（k(1O2)）和（·）OH（k(OH)）的二级反应速率常数，以及中性和阴离子 HO-PBDEs 的这些参数。阴离子的 k(d)、Φ、A、k(1O2)和 k(OH) 远高于中性分子，并且随溴化程度而变化。利用密度泛函理论（DFT）计算的分子参数用于构建结构-反应性方程。发现醚键强度、前沿分子轨道能量和电荷分布是控制光化学反应活性的固有结构特征。在北纬 45°的表面水中，在 7 月 15 日正午阳光的连续照射下，包括直接光解以及与（1）O（2）和（）OH 的反应在内的光降解半衰期范围为 0.7 至 60.1h。直接光解是主要途径。在给定 pH 值下，其他 HO-PBDEs 的光化学反应活性也可以根据结构-反应性方程进行估计，这对于 HO-PBDEs 的生态风险评估非常重要。
