荧光光谱研究垃圾堆场渗滤液水溶性有机物与汞作用

Fluorescence Spectroscopic Chracterization of the Complexation between Mercury(Ⅱ) and Dissolved Organic Matter

选取城市生活垃圾堆放场,采集渗滤液样品,对其水溶性有机物(DOM)进行分离提纯。采用荧光光谱分析方法,对DOM与Hg(Ⅱ)的相互作用过程进行了研究。荧光发射光谱分析表明,渗滤液DOM的组成物质结构简单,对Hg(Ⅱ)的配合能力强,配合Hg(Ⅱ)后表现出的荧光特性是各个荧光基团共同作用的结果。荧光激发光谱分析显示,在DOM与Hg(Ⅱ)的配合过程中,不同来源的—OH和—NH2都参与了配合作用;同步荧光光谱分析表明,Hg(Ⅱ)不仅能产生荧光猝灭效应,而且低浓度的Hg(Ⅱ)与DOM结合后还能使DOM中某些物质的刚性结构增强;三维荧光光谱证实,DOM与Hg(Ⅱ)的配合过程中,CO和—COOH与Hg(Ⅱ)形成了配位键,同时在此过程中,金属能级之间或其与蛋白类物质的能级之间发生了电荷位移跃迁。

In this study, conventional fluorescence spectroscopy in the excitation, emission and synchronous scan modes and three-dimensional fluorescence spectroscopy in the form of excitation-emission matrix of fluorescence intensity as a function of excitation and emission wavelengths were applied to study the complexation between DOM extracted from landfill leachates and Hg（ Ⅱ ） ions. The emission spectrum of DOM exhibited a broad peak with a center at 425 nm and a disorder change of the peak with increasing Hg（ Ⅱ ） concentrations, which suggested that the structure of DOM was comparatively simple and the fluorescence character of DOM-Hg（ Ⅱ ） complexes resulted from interaction of all fluorescence groups. The excitation spectrum of DOM showed that the intensities of two peaks at 392 and 458 nm both decreased with the addition of Hg（Ⅱ）, indicating that different sources, hydroxy and amido groups, were all involved in the DOM-Hg（ Ⅱ ） complexation process. Synchronous-scan excitation spectra of DOM-Hg（Ⅱ ） complexation showed that Hg（ Ⅱ ） not only produced fluorescence quenching effect, but also enhanced the rigid structure of DOM at a low concentration. The three-dimensional fluorescence spectra of DOM-Hg（ Ⅱ ） showed that the peaks A and B reduced strongly and the two peaks tended to shift toward longer wavelength with the concentrations of Hg（ Ⅱ ） increasing. These results indicated that protein-like matter reacted with Hg（ Ⅱ ） and there was a charge-transfer transition either between energy level in its ligand and a mercury energy level or between two mercury energy levels at the same time. Besides, the decrease in fluorescence intensity of peaks C and D in three-dimensional fluorescence spectra suggested that carbonyl and carboxyl formed bonds with Hg（ Ⅱ） when DOM was complexed with Hg（ Ⅱ）.