二苯甲酮类紫外防晒剂的光化学活性以及对典型有机污染物转化的影响

As a group of emerging contaminants, benzophenone UV filters (BP) have raised great concern to the public and scientific community. Previous studies have mostly focused on their fate and transformation in the environment as well as associated hazardous effects to ecosystems and human health. Little is currently known concerning their photochemistry activity. According to their molecular structures and our preliminary study, it is likely that BPs have photochemistry activity similar as natural organic matter, i.e., they can be irradiated by sunlight to form triplet BPs (3BP*) which react subsequently with dissolved oxygen to generate singlet oxygen (1O2). Both 3BP* and 1O2 are highly reactive and able to attack coexisted organic/inorganic species leading to their transformation/degradation. This study is designed to explore these reactions. A total of 12 commercial BPs will be selected and their photochemistry activity will be examined comprehensively. Quantitative structural-activity relationship (QSAR) will be established to elucidate the insights governing their photochemical activity. Based on these information, kinetics and mechanisms of the transformation of phenylurea herbicides, sulfonamide antibiotics, and estrogens in BP mediated photodegradation process will be examined systematically. The contribution of BP mediated photodegradation to the abiotic transformation of these contaminants in typical surface water conditions will be evaluated. In addition, formation of reactive halogen species due to the oxidation of halides (Cl- and Br-) by the reactive species generated from BPs upon sunlight irradiation will be investigated. Based on this, the transformation of estrogens in the presence of BPs in typical sea water conditions will be modeled and the role of halides will be quantified. Results of this study is of great importance to evaluate the environmental behavior of BPs.

二苯甲酮类紫外防晒剂（BP）是一类新兴污染物，目前对它们的研究主要集中在迁移转化和对生态系统、人体的毒性方面，对它们本身的光化学活性以及由此对共存污染物转化的影响则知之甚少。根据BP分子结构以及申请人前期研究，BP具有和水溶性天然有机质（NOM）类似的光化学活性，它们吸收阳光辐射后可生成激发三重态3BP*，然后和O2反应生成单重态氧（1O2）。这些活性中间体可敏化其它有机、无机物的转化和降解。本研究将系统考察BP的光化学活性和分子结构的相关性，并选择苯脲类除草剂、磺胺类抗生素和雌激素作物典型的污染物，研究它们在BP介导的间接光解中的降解机制，定量淡水环境中BP对它们转化的贡献。其次，本研究还将研究Cl-、Br-在BP介导的光化学过程中的转化，以及由此生成的活性卤中间体对雌激素转化的影响，构建海水中雌激素在BP介导的光化学反应中的降解动力学模型。本研究的结果将为评价BP的环境行为提供依据。

项目系统研究了一系列具有苯酮结构的新污染物，包括二苯甲酮防晒剂（BP）、喹诺酮抗生素（FQ）、酮洛芬（KTF）的环境光化学活性，以及对共存有机污染物转化的影响。结果表明，苯酮结构赋予了这些分子类似于天然有机质（NOM）的光化学活性，可有效吸收长波紫外光（UV-A，320-400 nm），生成激发三重态，后者和O2反应，生成单重态氧（1O2）。其中，诺氟沙星（NORF）和氧氟沙星（OFLO）的三重激发态（3FQ*）可有效促进苯脲除草剂、磺胺抗生素和对乙酰氨基酚的降解。3NORF*和3OFLO*的氧化还原电位分别为1.47和1.54V，它们与异丙隆的二级反应速率常数高达6.07×109 M-1s-1和1.51×1010 M-1s-1。3FQ*和苯脲除草剂的主要反应机制是单电子氧化。然而，NOM可还原苯脲单电子氧化的产物，因此对FQ敏化降解苯脲除草剂产生了抑制作用。Brˉ的存在会加速FQs光敏化降解对乙酰氨基酚。这主要归功于3FQ*氧化Brˉ生成Br•，后者可以快速与对乙酰氨基酚反应。当Brˉ浓度为3 mM时，对乙酰氨基酚在NORF和OFLO溶液中的光解速率分别提高了113.5%和56.3%。这的注意的是，在光解的过程中，FQ母体分子并不稳定，也发生了直接光解，但是溶液的光化学活性并没有随着母体的降解而消失。高分辨质谱分析表明，FQs的主要光解途径是脱氟和哌嗪部分的氧化，其核心苯酮结构仍然保持完整。因此，FQs的光解产物在很大程度上继承了母体的光化学活性。KTF和2,4-二羟基二苯甲酮（BP1）本身光敏化能力较弱，但光照后溶液光照后光化学活性显著增强。分析发现KTF光解后生成了3-乙基-α-羟基二苯甲酮（EtOH-BP）、3-乙基-α-氢过氧二苯甲酮（EtOOH-BP）、3-乙酰基二苯甲酮（AcBP）和3-乙基二苯甲酮（EtBP）四种产物。通过纳秒激光闪光光解（LFP）获得的瞬态吸收光谱证实了EtBP和AcBP可被激发生成三重态，其寿命分别为28和2.4 µs，具有很强的光敏活性。BP1光解生成了具有苯酮结构的2-[(2E)-1-氧-1,2-二氢萘-2-亚烷基]乙酸等产物，也具有很高的光化学活性，可以促进其它共存污染物的降解。本研究的结果将为评价苯酮结构的新污染物的环境行为提供依据。