单一的光谱技术不能对溶解性有机质(dissolved organic matters, DOM)的结构特征和来源进行全面的分析, 因此, 本研究选择紫外-可见光谱和三维荧光光谱技术相结合的方法, 对昆明松华坝库区表层土壤中DOM的组成结构和来源进行了研究。 结果表明, 所有样品的紫外-可见光谱曲线均呈现出相似的特征, 吸光度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。 A250/A365(波长在250和365 nm处紫外吸光度的比值)的范围在2.59～5.21之间, 说明DOM中主要物质为富里酸或者胡敏酸且分子量较高; SUVA254(单位DOC浓度在波长254 nm处的吸收系数)和SUVA260(单位DOC浓度在波长260 nm处的吸收系数)分别为1.19～3.00和1.15～2.89, 两者之间存在十分显著的相关性, 表明该地区土壤DOM的腐殖化程度相对较高并含有较多的疏水组分。 三维荧光光谱显示, 所有DOM样品中主要存在3个特征峰: 紫外光区类富里酸峰、 可见光区类富里酸峰和类腐殖酸峰, 而类蛋白峰不显著。 荧光指数(fluorescence index, FI)总体上接近于1.4, 表明该地区土壤DOM以外源输入为主; 自生源指标(autochthonous index, BIX)均小于1, 自生源特征不明显并且生物利用性较低, 这可能与当地较强的人类活动有关。 以上研究结果可以为进一步探讨DOM对有机或重金属污染物迁移转化的影响提供理论依据。

Single spectral technology can not comprehensively reflect structural features and sources of dissolved organic matter (DOM), therefore, in this study ultraviolet-visible (UV-Vis) and the three-dimensional excitation emission matrix fluorescence (3D-EEM) spectroscopy is applied to investigate the structure and origin of dissolved organic matters (DOM) from top soils on SongHuaba reservoir in Kunming. The results showed that the characters of all samples UV-visible spectra were similar. The ultraviolet absorbance of DOM samples decreased gradually with the wavelength increasing. There was an obvious shoulder absorption peak in the 250～280 nm band. The parameters of A250/A365 (absorbance at 250 to 365 nm) ranged from 2.59 to 5.21, which were illustrated that soil DOMs were composed of fulvic acid or humic acid with higher molecular weight. SUVA254 (the specific UV absorbance at 254 nm) and SUVA260 (the specific UV absorbance at 260 nm) were 1.19～3.00 and 1.15～2.89, which showed significant correlation, indicating that soil DOMs had a higher degree of humification and more hydrophilic components in this reservoir. The 3D-EEM spectrum revealed that all DOM samples had three special peaks, which were UV fulvic-like fluorescence, visible fulvic-like fluorescence and humic-like fluorescence, but protein-like fluorescence was not special. As a whole, the fluorescence index (FI) was closed to 1.4, which suggested that the soil DOMs in SongHuaba revesior were main from the external import. Autochthonous index (BIX) was less than 1, which suggested that the soil DOMs were affected by human activities and had low inherent character and bioavailability. These results serve to provide a theoretical basis for the further study of the DOMs effect on the migration and transformation of organic or heavy metal contaminants.