南淝河不同排口表层沉积物DOM光谱特征

在南淝河15个排口采集了表层沉积物样品,在测定了其中溶解性有机碳(SDOC)含量的同时,采用紫外-可见吸收光谱和三维荧光光谱分析方法,并结合PARAFAC模型对沉积物中溶解性有机质(DOM)的荧光组分和来源进行了解析.结果表明:南淝河不同排口表层沉积物SDOC的含量在0.28~0.95g/kg之间,平均为0.63g/kg;老城区采样点沉积物SDOC明显高于其他河段,特别是靠近污水厂尾水排放口沉积物SDOC明显高于其他采样点.南淝河沉积物紫外-可见光吸收系数aλ可以很好表征沉积物DOM含量相对大小,而光谱斜率S275-295和光谱斜率比SR反映出各采样点沉积物DOM中自生源组分的差异;利用PARAFAC模型解析出DOM四种荧光组分,其中较老的自生源腐殖质C2和新近类蛋白C4所占比例高.南淝河不同排口沉积物DOM自生源组分比例存在显著差异,其中老城区排口沉积物DOM以自生源组分为主,而上游排口沉积物DOM陆源组分所占比例较高,雨污排口和污水厂尾水排口虽以自生源为主,但陆源的贡献不可忽略.结果表明,光谱分析方法能够有效表征城市河道不同排口污染源强.

Spectral characteristic of dissolved organic matter (DOM) in the surface sediments from different discharging points along the Nanfei River in Hefei City,Anhui Province

The surface sediments samples were collected from 15 discharge ports of Nanfei River, an urban river in Hefei, Anhui Province. The fluorescence components and the sources of dissolved organic matter (DOM) in sediments were analyzed by the uses of dissolved organic carbon (SDOC) measurement, ultraviolet-visible absorption spectrum, and three-dimensional excitation emission matrix fluorescence spectroscopy (3D-EEM) combined with parallel factor analysis (PARAFCT). The results showed that the contents of SDOC ranged from 0.28to 0.95g/kg with the average of 0.63g/kg. The contents of SDOC in the old town were observed significantly higher than others, especially for the discharging ports near sewage plant effluents. It was found that the UV-Visible absorption coefficient (aλ) reflected well the relative quantity of DOM extracted from the sediments. The spectral slop (S) and the spectral slope ratio (SR) could be used to distinguish the difference in chemical composition of sediment DOM from different discharging ports. Further 3D-EEM analysis and PARAFAC mode studies revealed that there were four fluorescence components, and the autochthonous fractions including C2and C4components were the main sources of sediment DOM. It seems that there existed significant difference in the sources of sediment DOM from different discharging ports, and the sediment DOM of discharging ports from old town mainly originated from autochthonous production, while DOM of the sediment samples from upstream of Nanfei River showed significantly higher terrestrial source than that of the other samples. This study indicates that the spectrum analysis can be a useful tool to characterize the pollution intensity and discharging sources into the urban river.