长江溶解有机质三维荧光光谱的平行因子分析

利用三维荧光光谱(EEMs)研究了2009年9月长江上游至河口近4000km主流区域溶解有机质(DOM)的荧光组分特征及分布变化,结合紫外可见吸收光谱a350,旨在认识长江DOM的组成、来源和迁移转化过程.通过平行因子法(PARAFAC)解谱,得到3个类腐殖质组分H1、H2、H3及2个类蛋白质组分P1、P2.溶解有机碳(DOC)在上游浓度最低,在三峡库区万州附近明显增加,而后趋于稳定.荧光组分峰值之和(∑Fluo)呈类似趋势,和DOC相关性分析(R2=0.92)说明EEMs-PARAFAC可有效示踪溶解有机质的分布.其中蛋白质信号∑P约占∑Fluo的1/4,叶绿素a与∑P、DOC的弱相关性说明自生源不能主导DOM荧光组分分布;不同类腐殖质组分变化趋势不同,H3(Ex/Em:250/450~485nm)在库区后的水体有明显富集,而H1、H2占∑Fluo百分比则有所下降,a350也呈优先降解的趋势,反映了长江DOM迁移转化过程的选择性.

Characterization of DOM(dissolved organic matter) in Yangtze River using 3-D fluorescence spectroscopy and parallel factor analysis

Water samples were collected from Yangtze River basin across 4000km during September, 2009. Five fluorescence components (3 humic-like and 2 protein-like components) were identified by 3-dimension fluorescence spectroscopy (EEMs) combined with parallel factor analysis (PARAFAC) combined with a350 to elucidate composition, source and transformation processes of dissolved organic matter (DOM) in the Yangtze River. Dissolved organic carbon (DOC) increased remarkably from Wanzhou to the Three Gorge Dam and thereafter remained constant in the lower reach. The sum of all 5 components (∑Fluo) showed the similar trend of variation, which correlated linearly with DOC (R2=0.92) indicating that EEMs is a powerful tool to trace DOM in the Yangtze River. The protein-like component (∑P) accounted for 1/4 of ∑Fluo with apparently weak correlations with DOC and chlorophyll-a, which implied that the riverine DOM is not dominated by autochthonous production. Humic-like(H1, H2, H3) components showed different correlations with DOC, especially in the lower reach, where H3 (Ex/Em:250/450~485nm) was accumulated, while the other components (H1, H2) and a350 seemed to be degraded faster than H3. All the fact indicated that DOM might be subjected to selective biological and photochemical degradation processes in Yangtze River.