Beijing Engineering Research Center of Process Pollution Control, Division of Environment Technology and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100190, China; University of Chinese Academy of Sciences, Beijing, 100049, China; School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, United States.
Beijing Engineering Research Center of Process Pollution Control, Division of Environment Technology and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100190, China.
Water Res. 2017 Oct 1;122:299-307. doi: 10.1016/j.watres.2017.06.007. Epub 2017 Jun 5.
The transformation and detoxification of halobenzoquinones (HBQs), a class of emerging disinfection byproducts (DBPs), was studied in the presence of amino acids (AAs). The reaction activity of three HBQs with AAs generally ranked as 2-chlorobenzoquinone (CBQ) < 2,6-dichlorobezoquinone (DCBQ) < tetrachloroquinone (TCBQ), consistent with their halogenation degree and the calculated electron affinity (EA) results. According to mass spectrometry and density functional theory (DFT) calculations, AAs can easily covalently incorporate into HBQs via nucleophilic addition (CBQ and DCBQ) or substitution (TCBQ) through CNC or CSC linkages. Hydroxylation, nucleophilic reaction and decarboxylation were proposed to be the three major reaction pathways for HBQs transformation with AAs. HBQs firstly underwent the spontaneous hydrolysis, resulting in OH-HBQs formation. Then, nucleophilic addition/substitution of AAs occurred on HBQs and OH-HBQs to produce AA-HBQs/AA-HBQs-OH adducts. These adducts were subsequently oxidized into their corresponding decarboxylated forms. Based on the results of Luminous bacterium Q67 acute toxicity test, the toxicity of HBQs solution greatly decreased with AAs presented. The toxicity change was well explained by the lowest unoccupied molecular orbital energy (E) of formed products. Notably, the step that AAs nucleophilic bonded with HBQs led to the highest rise of E, which should be the most effective pathway for HBQs detoxification. This study shows that binding with amino nitrogen compounds should be an important process for HBQs transformation and detoxification, which helps to better understand the fate of this typical DBP in surface water.
含卤苯醌（HBQs）作为一类新兴的消毒副产物（DBPs），其在氨基酸（AAs）存在下的转化和解毒作用得到了研究。三种 HBQs 与 AAs 的反应活性通常为 2-氯苯醌（CBQ）<2,6-二氯苯醌（DCBQ）<四氯苯醌（TCBQ），与它们的卤化程度和计算出的电子亲合能（EA）结果一致。根据质谱和密度泛函理论（DFT）计算，AAs 可以通过亲核加成（CBQ 和 DCBQ）或取代（TCBQ）通过 CNC 或 CSC 键合，容易地与 HBQs 共价结合。提出了羟基化、亲核反应和脱羧反应是 HBQs 与 AAs 转化的三条主要反应途径。HBQs 首先经历自发水解，生成 OH-HBQs。然后，AAs 对 HBQs 和 OH-HBQs 发生亲核加成/取代反应，生成 AA-HBQs/AA-HBQs-OH 加合物。这些加合物随后被氧化成相应的脱羧形式。根据发光菌 Q67 的急性毒性试验结果，随着 AAs 的存在，HBQs 溶液的毒性大大降低。形成产物的最低未占据分子轨道能量（E）很好地解释了毒性的变化。值得注意的是，AAs 亲核键合与 HBQs 的步骤导致 E 的升高幅度最大，这应该是 HBQs 解毒的最有效途径。本研究表明，与氨基氮化合物的结合应该是 HBQs 转化和解毒的一个重要过程，有助于更好地了解这种典型的地表水中 DBP 的命运。
