拦河大坝对河流有色溶解有机质赋存特征的影响初探  

Impact of River Damming on the Characteristics of Riverine Chromophoric Dissolved Organic Matter

作　　者：向元婧 黄清辉[1] 

机构地区：[1]同济大学环境科学与工程学院,长江水环境教育部重点实验室,上海200092

出　　处：《水生态学杂志》2014年第6期1-6,共6页Journal of Hydroecology

基　　金：国家自然科学基金项目(41071301;40601095)

摘　　要：运用紫外-可见吸收光谱和三维荧光光谱技术,分析了长江三峡大坝上下游河水中有色溶解有机质(CDOM)的含量水平和荧光组分构成及其空间变化。结果表明,自三峡水库支流香溪河河口(回水区)向下游至三峡水库主库区,CDOM的紫外吸收系数(a355从1.30 m-1增至5.21 m-1)和类酪氨酸组分荧光强度及其在荧光组分中所占比例(从25%升至62%)均呈上升趋势,至三峡大坝附近达到全段峰值,而类腐殖质荧光强度及其在荧光组分中所占比例逐步下降;过坝后,CDOM吸收系数在黄陵庙处急剧降至全干流检测段最低(a355=0.95 m-1),但类腐殖质在荧光组分中所占比例达到全段最高(76%);再往下游至葛洲坝库区南津关处,CDOM吸收系数(a355=6.83 m-1)又回升至全段最高,其中类酪氨酸为绝对优势组分。水体类酪氨酸组分的增加主要源自水库浮游生物新生产活动以及微生物转化作用的增强;而CDOM的减少是因为颗粒物的吸附作用。拦河大坝形成的湖泊效应和下泄流过程将对河流有色溶解有机质的赋存特征有显著影响。The dissolved organic matter （ DOM） in natural waters plays an important role in global biogeochemical cycles and the microbial loop that is sequestering carbon on a global scale.Chromophoric （ or colored） dissolved organic matter （ CDOM） , a significant fraction of total DOM, absorbs light over a broad range of ultraviolet （ UV） and visible wavelengths.The primary sources of DOM in rivers include surface runoff, wastewater discharge and phytoplankton exudates.It has been reported that the DOM of reservoirs is influenced by the tributary inflow.Res-ervoirs, depending on residence time, can become more lacustrine and significantly alter phytoplankton and plank-tonic bacteria communities and nutrient dynamics but the influence on CDOM is not clear.In this study, we report the spatial dynamics of riverine CDOM in the reaches above and below Three Gorges Dam to provide preliminarily findings on the influence of river impoundment on the characteristics of CDOM.Water samples were collected along five transects from the Xiangxi River estuary （31 km above Three Gorges Dam） to Nanjinguan （38km below Three Gorges Dam） on June 3, 2008.Samples were filtered on site and transported to the laboratory for analysis using ul-traviolet-visible and fluorescence spectroscopy.In situ CDOM concentrations were also determined in the upper rea-ches of the Xiangxi River Bay and the Miaohe section of the Yangtze River.The absorption coefficient for CDOM atλ=355 nm （ a355 ） was measured by UV-vis spectroscopy and the composition of fluorescent components （ FDOM） was analyzed using three-dimensional fluorescence （ EEM） spectroscopy.From the upper reaches of Xiangxi River Bay to the Three Gorges Dam, the absorption coefficient increased from 1.30 m^-1 to 5.21 m^-1 .Fluorescence in-tensities also increased due to the increase in tyrosine （ protein-like） substances （25%in upper Xiangxi River Bay to 62%near Three Gorges Dam） and decrease in humic-like substances.At Huanglingmiao, just below the Three

关 键 词：有色溶解有机质 拦河大坝 紫外吸收系数 荧光强度 

分 类 号：X132[环境科学与工程—环境科学]