环滇池土壤溶解性有机质(DOM)的光谱特征及来源分析

摘要

Ultraviolet-visible (UV-Vis) and three-dimensional excitation emission matrix fluorescence (3D-EEM) spectroscopies,combined with parallel factor analysis were conducted to investigate the structure and origin of dissolved organic matters (DOM) from soils around Dianchi lake,Kunming.The results showed that the characteristics of all samples' UV-Visible spectra were alike.The absorption coefficient of DOM samples decreased gradually with the wavelength increasing.There was an obvious shoulder absorption peak in the 250~280 nm band.Additionally,in Chaihe reservoir and the east of Dianchi lake,the aromaticity (A250/A365),molecular weight (SR),humification degree (SUVA254) and hydrophobicity (SUVA260) of soil's DOM were all much higher than those at other three sampling sites.The 3D-EEM spectrum revealed that all DOM samples around Dianchi lake had four special peaks,which were UV fulvic-like fluorescence,visible fulvic-like fluorescence and two humic-like fluorescences.Fluorescence index (FI) and Autochthonous index (BIX) suggested that soil's DOM were main from the external import and had low protein-like components and bioavailability.Four fluorescence components were identified with parallel factor analysis and showed significant correlation (p<0.01),which were illustrated that the four fluorescence components had a similar source.In addition,the contribution rates of fulvic-like fluorescence component was the highest,which suggested that the content of fulvic acid material was relatively higher in soil's DOM.%利用紫外-可见光谱和三维荧光光谱技术,结合平行因子分析法,对环滇池地区土壤中溶解性有机质(dissolved organic matters,DOM)的结构特征和来源进行了研究.结果显示,所有样品的紫外-可见光谱曲线均呈现出相似的特征,吸收系数随着波长的增加而降低,并在250~280 nm波段存在一个明显的肩状吸收峰.柴河水库和滇池东部地区土壤DOM的芳香性(A250/A365)、分子量(SR)、腐殖化程度(SUVA254)和所含疏水组分(SUVA260)均高于其他三个区域.三维荧光光谱显示,环滇池土壤DOM中含有紫外可见光区类富里酸峰、可见光区类富里酸峰和两种类腐殖酸峰.荧光指数(fluorescence index,FI)和自生源指标(autochthonous index,BIX)均表明该地区土壤DOM有着典型的陆源特征,且类蛋白成分生成量较少,生物可利用性较低.平行因子分析法(PARAFAC)将土壤DOM分成四个荧光组分,四个组分之间有着非常显著的相关性(p<0.01),表示具有同源性.此外,类富里酸荧光组分对DOM的贡献率最大,说明土壤DOM中富里酸物质的含量相对较多.