典型酚类化合物水相光氧化产物光谱特征分析  

Spectrum Characteristic of Aqueous Photooxidation Products of Selected Phenolic Compounds

作　　者：李洋 高阳 张宁 吴水平 LI Yang;GAO Yang;ZHANG Ning;WU Shuiping(College of Environment and Ecology,Xiamen University,Xiamen 361102,China;Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies,Xiamen 361102,China)

机构地区：[1]厦门大学环境与生态学院,福建厦门361102 [2]福建省海陆界面生态环境重点实验室,福建厦门361102

出　　处：《环境科学与技术》2021年第6期74-83,共10页Environmental Science & Technology

基　　金：国家重点研发计划项目(2016YFC0502901);国家自然科学基金(41471390)。

摘　　要：生物质燃烧可直接排放棕色碳类物质(BrC),也可通过排放的亲水性酚类化合物的水相光解生成BrC,但初始浓度对光氧化产物光谱特征的影响研究较少。该研究选择3,5-二羟基苯甲酸、4-甲基邻苯二酚、2-甲氧基苯酚和2,6-二甲氧基苯酚进行水相溶液直接光照模拟,考察不同分子结构和不同初始浓度(0.1、0.5、1和5 mmol/L)对光解产物的影响。结果表明,在300 W高压汞灯光源照射下,溶液颜色都表现为从无色变为浅黄色,紫外-可见吸收随波长单调递减,显示有BrC的生成;0.1 mmol/L低浓度溶液出现了先变黄加深后变浅的光漂白现象,而其他高浓度溶液在365 nm处的吸光度呈逐渐增加趋势;光解速率呈现3,5-二羟基苯甲酸大于4-甲基邻苯二酚,以及2-甲氧基苯酚大于2,6-二甲氧基苯酚的差异,表明酚类化合物结构对光解过程有重要影响。结合三维荧光中心红移分析,推测酚类化合物的直接光解过程为有机自由基反应驱动的低聚过程。Burning biomass releases a large amount of brown carbon(BrC)into the atmosphere.Meanwhile,phenolic compounds emitted from biomass burning can undergo direct photolysis in aqueous solution in the atmosphere to form BrC.To date,there is few study about the effect of the initial concentration on the spectral characteristics of photooxidation products.In this study,the direct photolysis reaction of 3,5-dihydroxybenzoic acid,4-methylcatechol,2-methoxyphenol and 2,6-dimethoxyphenol were investigated using different initial concentrations(0.1,0.5,1 and 5 mmol/L).A yellowish solution was obtained under the irradiation of 300 W high-pressure mercury lamp.The UV-Vis absorption spectrum decreased monotonically with wavelength,indicating the formation of BrC substance.For the solution of low-concentration of 0.1 mmol/L,the solution varied gradually from colorless to yellow and then colorless again,suggesting that photobleaching occurred;however,for the solution of concentration higher than 0.1 mmol/L,the absorption spectrum at 365 nm increased with time.The calculated photolysis rates revealed that 3,5-dihydroxybenzoic acid reacted faster than 4-methylcatechol and 2-methoxyphenol reacted faster than 2,6-dimethoxyphenol,indicating the important effect of phenolic compound structure on photolysis process.The direct photolysis of phenolic compounds could be explained by the oligomerization process driven by the organic radical reaction based on the observed bathochromic shift in fluorescence spectrum.

关 键 词：酚类化合物 直接光解 紫外-可见吸收光谱 荧光光谱 棕色碳 

分 类 号：X131[环境科学与工程—环境科学]