三峡库区城镇化背景下河流DOM的吸收及荧光光谱特征

研究城镇化对河流溶解性有机质(dissolved organic matter,DOM)组分和化学结构、来源与迁移规律的影响,对水生态系统保护及生物地球化学循环研究具有重要意义.运用紫外-可见吸收光谱和三维荧光光谱技术,研究三峡库区不同城镇化程度的典型河流(桃花溪、南河和普里河)的DOM光谱学特征.结果表明,河流城镇化程度越高,DOM和有色溶解性有机质(chromophoric dissolved organic matter,CDOM)浓度越大,河流DOM的腐殖化程度和芳构化程度越小,疏水性组分越少,DOM中类蛋白物质相对浓度越高,DOM的新近自生源特性越强.河流DOM均以富里酸类为主(E3/E4均值 3. 5),CDOM浓度与DOM浓度显著正相关(P 0. 01),各河流DOM腐殖化程度(SUVA254)、芳构化程度(SUVA280)和疏水组分(SUVA260)极显著正相关(P 0. 01).桃花溪、南河、普里河的荧光指数均值为1. 715 7～1. 757 1,DOM的腐殖质来源均为外源输入和微生物、藻类生产两种方式混合,且以内源产生为主.

Absorption and Fluorescence Spectra of Dissolved Organic Matter in Rivers of the Three Gorges Reservoir Area Under the Background of Urbanization

Studying the influences of urbanization on the composition, chemical structure, source and migration of dissolved organic matter (DOM) in rivers is of great significance for aquatic ecosystem protection and biogeochemical carbon (C) cycling. The DOM spectroscopic characteristics of the three typical rivers (Taohuaxi, Nanhe, and Puli) with different urbanization levels in the Three Gorges Reservoir area were investigated using the ultraviolet-visible (UV-Vis) absorption spectrum and three-dimensional fluorescence spectroscopy. The results demonstrated that the higher the degree of urbanization in rivers, the greater the concentrations of DOM and chromophoric dissolved organic matter (CDOM), the lower the humification degree and aromaticity of DOM, the smaller the proportion of hydrophobic components, the higher the relative level of protein-like substance concentration in DOM, and the greater the contribution of DOM from freshly autochthonous origins. The DOM of the three rivers was dominated by fulvic acids (E3/E4>3.5), and CDOM concentration was positively correlated with the concentration of DOM (P<0.01). There were significant positive correlations between the humification degree (SUVA₂₅₄), aromaticity (SUVA₂₈₀), and hydrophobic component (SUVA₂₆₀) (P<0.01). The sources of humic substances in the DOM were mixed by terrestrial input and microbial or algae production (reflected by the fluorescence index averages of 1.7157-1.7571), and mainly from microbial sources.