三维荧光与神经网络研究城市河流沉积物孔隙水有机物组成与结构特征

应用三维荧光技术结合自组织神经网络方法，研究典型城市河流沉积物孔隙水中水溶性有机物(DOM)与颗粒性有机物(POM)组成结构及空间分布特征。自组织神经网络是一种非监督神经网络算法，能够从有机物三维光谱中提取不同的荧光组分，表征各组分的含量。沉积物是重要的有机碳库，而沉积物孔隙水中有机物的多寡可直接反映其环境特征。人们对水体中沉积物孔隙水中的DOM与营养盐特征的研究较多，而对POM的研究较少，尤其对重污染城市支流河的研究更少。因此，选取沈阳市白塔堡河为研究对象，沿河源、农村、城市区域河段采集沉积物孔隙水样品，提取DOM与POM，检测样品的三维荧光光谱。DOM的f_450/500值为1.82～1.91，表明DOM主要是微生物源;POM的f_450/500值为1.42～1.68，表明POM主要以陆地输入为主。自组织神经网络解析DOM与POM含有类酪氨酸、类色氨酸、类富里酸与类胡敏酸等物质，类酪氨酸主要源于新鲜的具有高氧化的类蛋白物质，而类色氨酸主要为微生物代谢产物。DOM的各组分丰度之和为POM的2倍，类酪氨酸平均相对丰度在50%以上，类色氨酸的平均相对丰度为18.8%～23.1%，类富里酸相对丰度比类胡敏酸的高，但两者在有机物组分所占比重小。通过主成分分析，DOM与POM特征呈现沿河源、农村、城市区域河段变化，表明白塔堡河深受人类活动的影响。

Characterizing Structural Composition of Dissolved and Particulate Organic Matter from Sediment Pore Water in a Urban River Using Excitation-Emission Matrix Fluorescence with Self-Organizing Map

Excitation-emission matrix (EEM) fluorescence with self-organizing map was applied to characterize structural composition and spatial distribution of dissolved (DOM) and particulate (POM) organic matter from sediment pore water in a typical urban river. Ten sediment pore water samples were collected from the mainstream of Baitabuhe River in Shenyang City of northeast China, along a human impact gradient, i.e. river source, rural and urban regions. DOM and POM were extracted from the pore water, and their EEM fluorescence spectra were measured. f_450/500 of DOM ranged from 1.82 to 1.91, indicating that DOM is mainly from microbial source; f_450/500 of POM ranged from 1.42 to 1.68, suggesting that POM derived from land. Four components were identified from DOM and POM fractions by self-organizing map, which included tyrosine-like, tryptophan-like, fulvic-like and humic-like matters. Tyrosine-like originated from fresh and less degraded material with a high potential for oxidation, which was considered as representative components of DOM and POM. Tryptophan-like was associated with microbial byproduct-like material, and can indicate microbial activities. The abundance sum of all components in DOM is roughly 2 times more than that in POM. The mean relative abundance of tyrosine-like was more than 50%, while tryptophan-like was about 18.6%～23.1%. Abundance of fulvic-like was much more than that of humic-like, but they were only a small proportion of organic matter fractions. Based on principal component analysis, the characteristics of DOM and POM distinctly were distributed along river source, rural region and urban region, proving that the river was deeply influenced by human activity.