光谱特征法辨识不同污染景观河道中溶解性有机物的组分与来源

Spectral feature method was used to identify the components and sources of dissolved organic matter in different polluted landscape channels

利用三维荧光光谱(EEMs)结合平行因子分析方法(PARAFAC)及紫外-可见光谱技术(UV-vis),对苏州古城区内不同污染状况的景观河道中溶解性有机物(DOM)的光谱特征和来源进行解析.结果表明,苏州古城区内景观河道水体总体上表现为氮、磷营养盐污染.水体中的DOM解析出4种荧光组分,分别为自源类色氨酸C1(λ_(Ex)/λ_(Em)=235(290) nm/349 nm)、陆源类腐殖质C2(λ_(Ex)/λ_(Em)=250(315) nm/403 nm)、类色氨酸和酪氨酸的混合物C3(λ_(Ex)/λ_(Em)=230(275) nm/319 nm)和UVA类腐殖质C4(λ_(Ex)/λ_(Em)=240(350) nm/459 nm).相关性分析表明各个组分之间具有同源性,荧光组分与氮类营养盐和叶绿素a(Chl a)存在显著相关性,说明DOM与氮营养盐迁移转化、藻类活动有关.景观河道DOM中类蛋白类物质含量最多,类蛋白类物质的总荧光强度比例为66.36%~76.84%,类腐殖质荧光强度比例为23.15%~34.74%.在4种污染类型水体中,组分C1和C4含量没有明显差距,组分C2和C3含量差距较大,有机主导型水体中C2含量最大,无机主导型水体C3含量最大.同时分析了水体中DOM的荧光指标和吸收光谱指标,发现各种表观污染类型水体中荧光指数FI、自生源指数BIX均较大,且腐殖化指数HIX小于3.5,腐殖化程度弱,主要为内源;有机主导型水体中吸收系数a_(254)最大,芳香性最强.各种类型水体中吸收系数比值E2/E3均小于3.5,E2/E4较大,光谱斜率比值S_(R)大于1,DOM相对分子量较小,河道水体DOM的来源中内源贡献较大.

In this paper, dissolved organic matter(DOM) spectral characteristics and sources of landscape water bodies with different apparent pollution conditions of Suzhou ancient city were analyzed, Based on excitation emission matrix spectroscopy(EEMs) technology combined with the parallel factor analysis(PARAFAC) and UV-vis spectra. The results show that the water body of the landscape river in the ancient city of Suzhou is generally polluted by nitrogen and phosphorous. Four components of DOM in water were identified by PARAFAC model, including the self-derived tryptophan C1(λ_(Ex)/λ_(Em)=235(290) nm/349 nm), the terrestrial humus C2(λ_(Ex)/λ_(Em)=250(315) nm/403 nm), the protein-like substance C3(λ_(Ex)/λ_(Em)=230(275) nm/319 nm) and the UVA humus C4(λ_(Ex)/λ_(Em)=240(350) nm/459 nm). Each component has homology, and the fluorescence component has significant correlation with nitrogen nutrients and chlorophyll a, indicating that DOM is related to the migration and transformation of nitrogen nutrients and the the growth of algae. The content of protein-like substances in the DOM of landscape water body was the largest, accounting for 66.36%~76.84% of the total fluorescence intensity, and the proportion of humus-like fluorescence intensity was 23.15%~34.74%.Among the four types of pollution landscape river water body, there was no significant difference in the contents of component C1 and C4, and a large difference in the contents of component C2 and C3.The content of C2 was the highest in the organic and the content of C3 was the highest in the inorganic.Fluorescence index FI and self-source index BIX in water of various apparent pollution types were all large, humic index HIX was less than 3.5, and humic degree was weak, which was mainly endogenous. The absorption coefficient a_(254) was the largest and the aromaticity was the strongest in the organic type. In all types of water, the absorption coefficient ratio E2/E3 was less than 3.5, E2/E4 was larger, the spectral slope ratio S_(R) was greater than 1, the relative molecular weight of DOM was smaller, and in the source of DOM of river water, endogenous contribution is relatively large.