平水期/枯水期南四湖溶解性有机物差异特征

Differences in Characteristics of Dissolved Organic Matter in Nansi Lake during Normal and Dry Seasons

南四湖是南水北调东线工程最大的调蓄湖泊,研究南四湖有色可溶性有机物(CDOM)的组成、来源与时空变化规律,对于保障东线调水水质具有重要意义。运用三维荧光光谱(EEMs)与平行因子分析模型(PARAFAC)等技术手段研究2019年5月及11月不同水文情景下南四湖CDOM组成与来源特征。结果表明,PARAFAC解析EEMs获得3种荧光组分,即微生物作用的类腐殖酸C1、陆源类腐殖酸C2和类色氨酸C3。其中组分C1和C3贡献较大,二者合计可达80%,表明南四湖水体自生源类CDOM含量可能高于外源输入。组分C1与C2荧光强度在平水期低于枯水期,组分C3荧光强度在平水期高于枯水期。不同水文时期,3种荧光组分高值普遍出现于入湖河口处。分析表明,吸收系数a(254)、比紫外吸收系数SUVA_(254)和荧光峰积分比值I_(C)∶I_(T)与3种组分荧光强度显著相关,其中荧光组分C1与a(254)显著正相关(r^(2)=0.320,P<0.01),这意味着CDOM吸收光谱及三维荧光光谱能有效揭示南四湖CDOM来源和光谱组成特征。

Nansi Lake is the largest regulating and storage lake in the eastern route of the South-to-North Water Diversion Project.It is thus of great significance to explore the composition,source and spatial-temporal variation of the chromophoric dissolved organic matter(CDOM)in Nansi Lake to ensure the water quality of the eastern route.The composition and source characteristics of the CDOM in Nansi Lake under different hydrological scenarios were analyzed by excitation-emission matrices(EEMs)and parallel factor analysis(PARAFAC)in May and November 2019.Three fluorescent components were obtained through EEMs analyzed by PARAFAC,including the microbial humic-like C1,the terrestrial humic-like C2 and the tryptophan-like C3.Among them,the relative contribution of the components C1 and C3 to Nansi Lake was relatively large,and their combined contribution reached 80%,indicating that the content of the autochthonous CDOM in Nansi Lake might be higher than that of the exogenous input.The fluorescence intensity of the component C1 and C2 in the normal season was lower than that in the dry season,while that of the component C3 in the normal season was higher than that in the dry season.In different hydrological periods,the high values of the three fluorescence components generally occurred in the estuary of the lake.The correlation analysis showed that absorption coefficient a(254),specific UV absorption coefficient(SUVA_(254))and fluorescence peak integral ratio(I_(C)∶I_(T))were significantly correlated with the fluorescence intensity of the three components,among which the fluorescence component C1 was significantly positively correlated with a(254)(r^(2)=0.320,P<0.01),indicating that the CDOM absorption and fluorescence spectroscopy could effectively reveal the source and spectral characteristics of the CDOM in Nansi Lake.