基于EEMs及PARAFAC的洪湖、东湖与梁子湖CDOM组成特征分析

国内外关于长江中下游地区如洪湖、东湖及梁子湖等大中型浅水湖泊DOM组成特征的分析较少，本文基于2007年9月—10月洪湖、东湖与梁子湖34个站点野外实地采样数据，运用三维荧光图谱(EEMs)与平行因子分析(PARAFAC)模型，着重分析了三个湖泊CDOM吸收荧光特性及组成特征。结果表明，CDOM在350 nm处吸收系数a(350)在三个湖泊表现为洪湖极显著高于东湖与梁子湖(p<0.001);三个湖泊CDOM光谱斜率S_280～500与a(350)呈极显著负相关(R2=0.781, p<0.001)且洪湖S_280～500值极显著低于东湖与梁子湖(p<0.01);光谱斜率比值S_R值也表现为洪湖显著低于东湖与梁子湖(p<0.05)。PARAFAC模型解析得到两个类腐殖质组分(C1, C2)，两个类蛋白质组分(C3，C4)，其中组分C1与C2呈极显著正相关(R2=0.884，p<0.001)，组分C3与C4亦为极显著正相关(R2=0.677，p<0.001)，这表明三个湖泊CDOM组分C1与C2，C3与C4来源相似，然而统计结果并未发现四个荧光组分与DOC及Chl-a浓度之间存在任何显著性相关关系。三个湖泊荧光指数FI₂₅₅(HIX)，FI₂₆₅，FI₃₁₀(BIX)与FI₃₇₀值均表现为东湖显著高于梁子湖(p<0.05)，极显著高于洪湖(p<0.01)，这意味着东湖富营养化程度高于洪湖与梁子湖。

Characterizing Chromophoric Dissolved Organic Matter (CDOM) in Lake Honghu,Lake Donghu and Lake Liangzihu Using Excitation-Emission Matrices (EEMs) Fluorescence and Parallel Factor Analysis (PARAFAC)

Little is known about DOM characteristics in medium to large sized lakes located in the middle and lower reaches of Yangtze River, like Lake Honghu, Lake Donghu and Lake Liangzihu. Absorption, fluorescence and composition characteristics of chromophoric dissolved organic matter (CDOM) are presented using the absorption spectroscopy, the excitation-emission matrices (EEMs) fluorescence and parallel factor analysis (PARAFAC) model based on the data collected in Sep.-Oct. 2007 including 15, 9 and 10 samplings in Lake Honghu, Lake Donghu and Lake Liangzihu, respectively. CDOM absorption coefficient at 350 nm a(350) coefficient in Lake Honghu was significantly higher than those in Lake Donghu and Lake Liangzihu (t-test, p<0.001). A significant negative correlation was found between CDOM spectral slope in the wavelength range of 280～500 nm (S_280～500) and a(350) (R2=0.781, p<0.001). The mean value of S_280～500 in Lake Honghu was significantly lower than those in Lake Donghu (t-test, p<0.01) and Lake Liangzihu (t-test, p<0.001). The mean value of spectral slope ratio SR in Lake Honghu was also significantly lower than those in Lake Donghu and Lake Liangzihu (t-test, p<0.05). Two humic-like (C1, C2) and two protein-like fluorescent components (C3, C4) were identified by PARAFAC model, among which significant positive correlations were found between C1 and C2 (R2=0.884, p<0.001), C3 and C4 (R2=0.677, p<0.001), respectively, suggesting that the sources of the two humic-like components as well as the two protein-like components were similar. However, no significant correlation has been found between those 4 fluorescent components and DOC concentration. The fluorescence indices of FI₂₅₅(HIX), FI₂₆₅, FI₃₁₀(BIX) and FI₃₇₀ in Lake Donghu were all significantly higher than those in Lake Liangzihu (t-test, p<0.05) and Lake Honghu (t-test, p<0.01), indicating that the eutrophication status in Lake Donghu was higher than Lake Honghu and Lake Liangzihu.