黑龙江流域典型断面水体DOM荧光特性分析

为研究黑龙江流域水环境腐殖质的组成、时空分布特征及来源特征，通过野外调查、静态浸泡试验和动态淋溶试验，利用三维荧光激发-发射矩阵结合平行因子分析（EEM-PARAFAC）及荧光定量指标，分析水体DOM（dissolved organic matter，溶解性有机物）的荧光特性和来源特征.结果表明:①ρ（COD_Mn）在平水期和丰水期出现了畸高现象，平水期和丰水期水体DOM的相对含量高于冰封期.水体DOM识别出4种荧光组分长波段类腐殖酸（C1）、短波段类腐殖酸（C2）、类富里酸（C3）和类色氨酸（C4）]，其中类腐殖质总贡献率在50%以上，属于类腐殖质主导型.平水期、丰水期和冰封期水体DOM的FI（荧光指数）值分别为1.48~1.61、1.51~1.63和1.52~1.79，BIX（生物源指数）值分别为0.56~0.75、0.55~0.73和0.61~0.92，HIX（腐殖化指数）值分别为5.84~13.42、5.70~15.78和2.84~12.05，表明水体DOM是陆源和自生源贡献相结合，具有自生源特征和强腐殖质特征.②通过静态浸泡试验模拟土壤溶解，识别出5种荧光组分，除C1~C4外，还识别出类酪氨酸（C5）；通过动态淋溶试验模拟降雨过程，识别出4种荧光组分（C1~C4）.土壤DOM的荧光特性与水体DOM相似，表明水体DOM与土壤DOM具有相似的来源.③3个水期各荧光组分的荧光强度均与ρ（DOC）呈线性相关.其中，C1、C2和C3的荧光强度与ρ（DOC）均呈显著线性相关，平水期、丰水期、冰封期C1的相关系数分别为0.776 2、0.852 4和0.956 8，C2的相关系数分别为0.478 3、0.265 9和0.878 4，C3的相关系数分别为0.658 2、0.802 5和0.954 5；但C4的相关系数差别较大，分别为-0.064 4、0.021 9和0.847 4，说明类腐殖质荧光组分是DOC的主要来源.研究显示，黑龙江流域水体DOM以类腐殖质为主，水体DOM具有强腐殖质特征，源头水的背景值较高. 

Fluorescence Characteristics Analysis of DOM in Typical Section of Heilongjiang River Basin

The composition, temporal and spatial distribution and source characteristics of humus in the Heilongjiang River Basin were studied via field investigations, static immersion and leaching dynamic experiments. Fluorescence characteristics and sources of dissolved organic matter (DOM) in typical Heilongjiang River Basin were analyzed by EEM-PARAFAC. The results showed that: (1) The concentration of COD_Mn was abnormally high during the normal and wet seasons. The relative content of DOM was much higher than that during the dry season. Four fluorescence components, including UVA humic-like substances (C1), UVC humic-like substances (C2), marine humic-like substances (C3) and tryptophan-like substances (C4) were detected in a typical Heilongjiang River Basin. Among them, the total contribution of humic-like substances accounted for over 50%. Therefore, humic-like substances were the most important factors affecting DOM in the Heilongjiang River Basin. The fluorescence index (FI) values of DOM during the normal, wet and dry seasons were 1.48-1.61, 1.51-1.63 and 1.52-1.79, respectively. The biological source index (BIX) values of DOM during the normal, wet and dry seasons were 0.56-0.75, 0.55-0.73 and 0.61-0.92, respectively, and the humification index (HIX) values of DOM were 5.84-13.42, 5.70-15.78 and 2.84-12.05, respectively, indicating that DOM mainly came from land sources and autogenous sources with autogenous source characteristics and significant humus characteristics. (2) Static immersion and dynamic leaching experiments were carried out to simulate soil dissolution and rainfall process. Consequently, five fluorescence components were detected during leaching process. In addition to C1-C4, tyrosine-like substances (C5) were found. Due to similar fluorescence characteristics of DOM in soil and water, it is concluded that the DOM in water and soil had similar sources in the Heilongjiang River Basin. (3) A linear correlation between fluorescence component intensity and DOC concentration during the normal, wet and dry seasons was observed. Humic-like substances and marine humic-like substances had significant linear correlation with DOC concentration. The correlation coefficients of C1, C2 and C3 during the normal, wet and dry seasons were 0.7762, 0.8524 and 0.9568, 0.4783, 0.2659 and 0.8784, 0.6582, 0.8025 and 0.9545, respectively. In comparison, there was a large gap between the correlation coefficient between C4 and DOC concentration. The correlation coefficients of C4 during the normal, wet and dry seasons were -0.0644, 0.0219 and 0.8474, respectively, indicating that the humic-like fluorescence components were the main sources of DOC in the Heilongjiang River Basin. In summary, the humic-like components were the main components of water DOM in the Heilongjiang River Basin. The water body had obvious DOM characteristics, and the background value of source water was relatively high.