藻源性湖泛水体显黑颗粒的元素形态分析与鉴定

Identification of black suspended particles in the algae-induced black bloom water column

湖泛现象是我国超富营养化浅水湖泊面临的最严峻环境问题之一,水体发黑、发臭是湖泛水体最显著和基本的物理特征.针对太湖湖泛显黑颗粒缺乏从元素形态直接给出证据的问题,针对室内模拟藻体和沉积物存在下形成的湖泛水体,采用多种图谱分析技术,对厌氧截留分离的显黑颗粒物质及其化学组成和元素形态进行了分析鉴定.扫描电镜-X射线能谱分析与荧光光谱分析表明:湖泛水体显黑颗粒物质以藻类残体和悬浮沉积物颗粒物为主,其组成元素以C、O、Si为主;与未发生湖泛的对照样相比,湖泛水体显黑颗粒物样品中具有更高的Fe、S含量.X射线光电子能谱Fe、S微区分析进一步表明:湖泛显黑颗粒物样品中Fe主要以Fe(Ⅱ)的形式存在、S则以还原态S2-的形式赋存,两者具有共同化合成Fe S的充要条件.因此,缺氧厌氧条件下,湖泛水体的显黑物质组成是Fe S,它可由水体中Fe2+和ΣS2-通过化学共沉淀形成,并主要通过吸附于悬浮颗粒物之上而使得整个水柱呈现黑色,指示湖泛的暴发过程和维持状态.

The black bloom phenomenon is one of the most serious problems in some hyper-eutrophic shallow lakes in China. The black colour and offensive odour were their most significant and basic physical characteristics. However,no firming evidences had been presented to explain what the black causing particles were in the black bloom water. In this research,the algae-induced black bloom was simulated and the chemical compositions of black suspended particles which were intercepted under anaerobic condition after the algae-induced black bloom simulation experiment were analyzed using multi X-ray based approaches. Scanning electron microscope-energy dispersive X-ray spectroscopy and X-ray fluorescence spectrometer analysis showed that algae residues and suspended sediment particles were the main substances and C,O,and Si were the main elements of these black particles. Compared to the check samples,black bloom suspended particles performed higher Fe and S contents. Detailed X-ray photoelectron spectroscopy analysis for Fe and S proved that Fe were mainly in the Fe（ Ⅱ） form while S were mainly in S2-form and the majority of them co-existed in the form of Fe S. Therefore,in the hypoxic and anoxic black bloom water column,abundant Fe2 ＋and ΣS2-could co-precipitate into Fe S. These black Fe S could suspend in the water column or absorb on suspended particles,which caused the black color of the water and marked the formation of the black bloom.