溶解性有机物(DOM)与区域土地利用的关系:基于三维荧光-平行因子分析(EEM-PARAFAC)

溶解性有机物（DOM）是水体质量的综合性指标，反映了流域内经济发展和治理保护等多方面因素，可为流域水体保护提供依据.本研究采集了宁波市4个不同城市化程度的区域内的河流样本，运用三维荧光结合平行因子分析法（EEM-PARAFAC）对水体中DOM进行解析，探讨了区域土地利用与DOM的关系.结果表明城市化在含量和组成两方面影响了流域水体中DOM的特征.城市区域（DOC=3.18 mg·L^-1）和城乡结合区域（DOC=7.45 mg·L^-1）水体中DOM的浓度远高于城市化程度较低的农村区域（DOC为2.16~2.62 mg·L^-1，ANOVA，P<0.001）.EEM-PARAFAC解析得到7个荧光组分，主要可归为类腐殖质和类蛋白质类物质.其中，城市区域DOM以类腐殖质物质为主，占比达到61.3%；而城乡结合区域由于受到更多的生活污水排放影响，类蛋白质物质的比例最高为59.4%；相比之下，农村区域虽然DOM浓度相对较低，但类腐殖质物质占比达63.6%~65.7%，面源污染是主要原因.主成分分析表明城市化发展对水质具有重要影响，在城市化初期污染主要来源于生活和工业污染源，当城市化到一定水平污染物更多来源于路面径流.本研究表明EEM-PARAFAC可以半定量辨析水体污染源，可为不同的区域水质恢复与治水策略制定提供针对性数据支撑.

Analysis of the Relationship Between Dissolved Organic Matter (DOM) and Watershed Land-use Based on Three-dimensional Fluorescence-Parallel Factor (EEM-PARAFAC) Analysis

Dissolved organic matter (DOM) is a characteristic index of water quality, and reflects many factors, such as the economic development and protection policies of watershed. In this study, surface water samples were collected from four watersheds with different levels of urbanization in Ningbo. The DOM was analyzed using an excitation-emission matrix combined with parallel factor analysis (EEM-PARAFAC) to explore the relationship between land-use and DOM. The results show that the urbanization level affected both the amount and the composition of the DOM in the studied watersheds. The concentrations of DOM evaluated by dissolved organic carbon (DOC) in urban areas (DOC=3.18 mg·L^-1) and an urban-rural combined area (DOC=7.45 mg·L^-1) were much higher than those in rural areas with low urbanization (DOC between 2.16 and 2.62 mg·L^-1, ANOVA, P<0.001). A total of seven PARAFAC components were identified in the studied watersheds, mainly including humic-like and protein-like substances. In the highly urbanized area, DOM was mainly composed of humic-like substances, with a proportion of 61.3%. However, the water samples from the urban-rural combined area exhibited a high proportion (59.4%) of protein-like substances, indicating a strong influence of sewage and industrial discharge. In contrast, although the DOM amounts in rural areas were relatively low, the proportions of humus-like substances were high, ranging from 63.6% to 65.7%. Agricultural non-point sources were the main contributor to DOM in these areas. Moreover, the results suggest that the urbanization process could intensify the damage to the surface waters. At the initial stage of urbanization (i.e., urban-rural combined area), contaminants are mainly discharged from sewage and industrial sources; when urbanization reaches a certain level, e.g., with a well-constructed sewage collection system, water contaminants originate more from surface runoff rather than sewage. The results of this study suggest that the EEM-PARAFAC technique can provide semi-quantitative source tracking of surface water, as well as an inexpensive and effective tool for policy makers to overcome the insensitivity of general water quality indices.