Fluorescent properties of dissolved organic matter as a function of hydrophobicity and molecular weight: case studies from two membrane bioreactors and an oxidation ditch
Fluorescent properties of dissolved organic matter as a function of hydrophobicity and molecular weight: case studies from two membrane bioreactors and an oxidation ditch
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溶解有机物的荧光特性与疏水性和分子量的关系：两个膜生物反应器和氧化沟的案例研究
DOI：
10.1039/c5ra23167a
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发表时间：
2016
期刊：
影响因子：
3.9
通讯作者：
Xia Huang
中科院分区：
文献类型：
--
作者：
Kang Xiao;Jian-Yu Sun;Yue-Xiao Shen;Shuai Liang;Peng Liang;Xiao-Mao Wang;Xia Huang
溶解性有机物（DOM）在污水处理系统中起着重要的作用。荧光是DOM的一个重要性质，它在DOM的表征中有着广阔的应用前景，但很少被扩展到探测基本的物理化学性质，如疏水性和分子量。本研究探讨了荧光特性和疏水性/分子量的DOM之间可能存在的联系，通过案例研究，从三个污水处理厂（两个膜生物反应器和一个氧化沟）。利用激发-发射矩阵（EEM）光谱和尺寸排阻色谱荧光检测技术，研究了不同疏水/亲水性和分子量组分DOM的荧光特性。使用荧光区域积分、平行因子分析、荧光光谱指数和基于荧光团能级的新型能量映射技术解释EEM光谱。结果发现，对于所有三种植物，DOM的疏水部分具有更高的荧光强度/UV吸光度（指示更高的量子产率）以及更大的斯托克斯位移比亲水部分。较低分子量的馏分一般表现出较高的荧光强度/总有机碳（指示较高的荧光团密度），在稍小的激发和发射波长的荧光分布。这些现象通过分析激发/发射过程中的荧光团能量状态进行了解释。DOM分子中π共轭体系的尺度可以作为疏水性/分子量和荧光性质之间相关性的中间因素。这些相关性可能有助于开发荧光探针的DOM特性在废水处理厂的过程监测。
Dissolved organic matter (DOM) plays a substantial role in wastewater treatment systems. Fluorescence is an important property of DOM and its use is promising for DOM characterization, but has rarely been extended to probing the basic physicochemical properties such as hydrophobicity and molecular weight. This study explores the possible linkages between the fluorescence properties and hydrophobicity/molecular weight of DOM, through case studies from three wastewater treatment plants (two membrane bioreactors and one oxidation ditch). The fluorescence properties of different hydrophobic/hydrophilic and molecular-weight fractions of DOM were obtained using excitation–emission matrix (EEM) spectroscopy and size-exclusion chromatography with fluorescence detection. The EEM spectra were interpreted using techniques of fluorescence regional integration, parallel factor analysis, fluorescence spectroscopic indices, and a novel energetic mapping based on fluorophore energy levels. It was found that for all the three plants, the hydrophobic fractions of DOM had a higher fluorescence intensity per UV absorbance (indicating a higher quantum yield) as well as a larger Stokes shifts than the hydrophilic fraction. The lower-molecular-weight fractions generally exhibited a higher fluorescence intensity per total organic carbon (indicating a higher fluorophore density), with the fluorescence distribution at slightly smaller excitation and emission wavelengths. These phenomena were explained via analysis of the fluorophore energy state during the excitation/emission process. The scale of the π-conjugated system in DOM molecules may serve as an intermediate factor in the correlations between the hydrophobicity/molecular weight and the fluorescence properties. These correlations may assist in developing fluorescent probes for the DOM characteristics during the process monitoring of wastewater treatment plants.