利用三维荧光光谱研究了大沽河流域地下水中溶解有机物(DOM)的荧光组分类型及其空间分布与变化, 并与地表河水进行了比较。 基于平行因子分析模型在大沽河流域识别出2个类腐殖质组分及1个类蛋白质组分。 研究区域上、 下游地下水中各荧光组分的强度低, 但中游区域呈现高值区, 与人为污染的下渗输入以及为阻止海水入侵而修建的截渗墙对地下水循环模式的改变有关。 地下水DOM以类腐殖质组分为主, 类蛋白质组分平均只占15%, 不及地表河水的一半, 其新鲜度指数(β/α)也低于河水但荧光指数(FI)、 腐殖化指数(HIX)高于河水, 表明地下水DOM的腐殖化程度更高, 与地下水停留时间长、 微生物降解作用的贡献更为显著有关。 本研究揭示, 三维荧光指纹技术可区分天然背景及人为活动对地下水中DOM含量及性质的影响, 是研究地下水环境中的碳循环过程及其影响因素的有用工具。

The fluorescent properties of dissolved organic matter (DOM) from groundwater in the coastal Dagu River watershed, North China were determined using excitation-emission matrix spectroscopy (EEMs) analysis. Surface water DOM samples were also investigated for comparison. Two humic-like components (C1: 250, 355/472 nm; C2: < 240, 325/400 nm) and one protein-like component (C3: <240, 280/340 nm) were identified using parallel factor analysis. Low intensities for all components were observed in groundwater DOM from the upper and lower reaches of the study area. However, higher abundances of these components occurred in the middle reaches, reflecting the combined effect of seepage of surface water with strong anthropogenic pollution and the alteration of groundwater circulation due to cutoff as a result of the construction of a cutoff wall since the late 1990s. The humic-like components were dominant in groundwater DOM, with the average percentage of the protein-like component being only 15%, which was less than half of the corresponding percentage in surface water DOM. The freshness index in groundwater DOM was lower than the surface water samples, while the fluorescence index and humification index were higher than in the latter. These indices demonstrated the much higher degree of humification for groundwater DOM, which may be related to the longer residence time of groundwater and greater contribution of microbial degradation in the aquifer environment. This study demonstrated that EEMs could distinguish between the effects of natural background and human activities on the quantity and characteristics of the groundwater DOM, and thus could be a useful tool for studing the carbon dynamics and the controlling factors in groundwater systems.