三峡库区城镇化影响下河流DOM光谱特征季节变化

三峡库区城镇化进程对河流溶解性有机质（dissolved organic matter，DOM）的组成和输运具有重要影响.本文选取三峡库区高城镇化河流桃花溪和低城镇化河流普里河，于春季（4月）和夏季（8月）采集水样，运用紫外-可见吸收光谱和三维荧光光谱技术，分析DOM的季节变化和空间特征.结果表明，桃花溪和普里河的DOC浓度、S_275-295（短波段光谱斜率）、S_R（光谱斜率比）、BIX（新近自生源特征）和Fn（280）（类蛋白物质相对浓度）均为夏季>春季，CDOM浓度、CDOM/DOC、SUVA₂₅₄（芳香性结构）、SUVA₂₆₀（疏水性组分）、E3/E4（富里酸所占比例）、S_350-400（长波段光谱斜率）和HIX（腐殖化程度）均为春季>夏季.高城镇化桃花溪的DOC、CDOM浓度、S_R、Fn（280）、BIX和FI高于低城镇化普里河，CDOM/DOC、SUVA₂₅₄和SUVA₂₆₀低于普里河.两河流沿水流方向随城镇化增加，SUVA₂₅₄和SUVA₂₆₀逐渐减小，Fn（280）逐渐增大.春、夏季两河流DOM腐殖质来源均为陆源输入与内源产生两种方式混合，且均以内源居多，DOM均具有中度新近自生源特征.研究反映了城镇化对河流DOM组成和来源的影响.

Seasonal Variation of DOM Spectral Characteristics of Rivers with Different Urbanization Levels in the Three Gorges Reservoir Area

The urbanization process of the Three Gorges Reservoir area (TGRA) shows important impacts on the formation, migration, and transportation of dissolved organic matter (DOM) in rivers. In this study, a high-urbanized river (Taohuaxi) and low-urbanized river (Pulihe) in the TGRA were selected and water samples were collected in spring (April) and summer (August) to analyze the seasonal and spatial characteristics of DOM in the rivers using UV-Vis absorption spectroscopy and three-dimensional fluorescence spectroscopy. The DOC, S_275-295 (the spectral slope of the short wavelength range), S_R (spectral slope ratio), BIX (recent autochthonous contribution), and Fn(280) (relative importance of protein-like substances) of the Taohuaxi and Pulihe Rivers were higher in summer (August) than in spring (April), and CDOM concentration, CDOM/DOC, SUVA₂₅₄ (aromatic structure), SUVA₂₆₀ (hydrophobic component), E3/E4 (proportion of fulvic acid), S_350-400 (the spectral slope of the long wavelength range), and HIX (the degree of humification) were higher in spring than in summer. The overall averages of the DOC, CDOM concentration, S_R, Fn (280), BIX, and FI were higher in the high-urbanized Taohuaxi River than the low-urbanized Pulihe River, whilst the CDOM/DOC, SUVA₂₅₄, and SUVA₂₆₀ were lower in the Taohuaxi River. With the increase of urbanization along the water flow pathways, SUVA₂₅₄ and SUVA₂₆₀ gradually decreased, while Fn (280) gradually increased. The humus source (FI) of the two rivers in spring and summer is mixed and includes terrigenous and biological sources (plankton and algae) but is mostly endogenous. Furthermore, DOM is characterized by a moderately recent autochthonous contribution. Our study implies a large impact of urbanization on the composition and sources of DOM.