Gao Jie, Jiang Tao, Yan Jin-long, Wei Shi-qiang, Wang Ding-yong, Lu Song, Li Lu-lu
Huan Jing Ke Xue. 2014 Sep;35(9):3397-407.
Three-dimensional fluorescence spectroscopy combined with ultraviolet-visible absorption spectra was used to investigate the photobleaching process of dissolved organic matter (DOM) sampled from Fujiang River (FJ), Jialingjiang River (JLJ) and the confluence (FJ-JLJ) under natural solar radiation. The results indicated that obvious photochemical degradation of colored dissolved organic matter (CDOM) concentration [ α(280) ] and all fluorescence peaks intensity (A, C, M and T) occurred under natural solar radiation, and the degradation degree was in order of JLJ > FJ-JLJ > FJ. Photobleaching properties of DOM samples from different locations showed significant differences, which could be partially explained by the sampling sites surroundings including various landuse types, and dilution effect of river confluence. Light-induced bleaching activity of JLJ samples, which was mainly terrestrial input from forest system, was the highest as compared to the lowest activity of FJ samples, which was predominated by urban inputs. Samples from confluence were in the middle. Additionally, the spectrum slope(S) and absorbance ratio (A250/A350) were increased, while the humification index(HIX) was decreased with increasing irradiation time, which can be used as important indicators for photobleaching properties changes during the process. More importantly, the predominantly allochthonous (terrigenous) characteristics of DOM almost showed a tendency of transferring to autochthonous (authigenic) characteristics due to photobleaching. Especially, IT/Ic firstly decreased and then increased significantly in the process. Thus the photodegradation process may exaggerate DOM autochthonous contribution, and further interfere with the assessment of anthropogenic impacted-water quality by using IT/Ic. In addition, mechanisms of light-induced DOM degradation process consistently showed by absorption and fluorescence spectrum parameters suggested the validation of analyzing DOM geochemical characteristics by the two important spectra tools.
采用三维荧光光谱结合紫外-可见吸收光谱，研究了涪江（FJ）、嘉陵江（JLJ）及其交汇处（FJ-JLJ）采集的溶解有机物（DOM）在自然太阳辐射下的光漂白过程。结果表明，在自然太阳辐射下，有色溶解有机物（CDOM）浓度[α(280)]和所有荧光峰强度（A、C、M和T）均发生了明显的光化学降解，降解程度为JLJ>FJ-JLJ>FJ。不同地点DOM样品的光漂白特性存在显著差异，这可以部分归因于采样点周围的各种土地利用类型以及河流交汇处的稀释效应。与主要受城市输入影响的FJ样品的最低活性相比，主要来自森林系统陆地输入的JLJ样品的光致漂白活性最高。交汇处的样品处于中间水平。此外，随着照射时间的增加，光谱斜率（S）和吸光度比（A250/A350）增大，而腐殖化指数（HIX）减小，这些可作为该过程中光漂白特性变化的重要指标。更重要的是，由于光漂白作用，DOM主要的外源（陆源）特征几乎呈现出向内源（自生）特征转变的趋势。特别是，在此过程中IT/Ic先降低后显著升高。因此，光降解过程可能会夸大DOM的内源贡献，并进一步干扰利用IT/Ic对受人为影响水质的评估。此外，吸收光谱和荧光光谱参数一致显示的光致DOM降解过程机制，表明了利用这两种重要光谱工具分析DOM地球化学特征的有效性。
