南漪湖上覆水溶解性有机质的光谱特征

为考察南漪湖上覆水中溶解性有机质(DOM)的光谱特征与来源,采用紫外-可见光吸收光谱(UV-Vis)与三维荧光光谱(EEMs)为工具,并结合平行因子分析(PARAFAC)、荧光区域积分分析(FRI)、相关性分析、主成分分析与聚类分析对DOM进行定性与定量分析.结果显示,UV-Vis参数a(440)、E₂/E₃、E₃/E₄、S_R表明DOM具有腐殖化特征与自生源特征,且E₂/E₃、E₃/E₄与a(440)呈显著正相关关系(P<0.01,P<0.05),S_R与a(440)无显著相关关系(P>0.05),说明腐殖酸浓度越高则DOM相对分子量越大,但无法依据腐殖酸浓度大小判断DOM来源.根据a(440)计算获得溶解性有机碳(DOC)平均浓度为26.79mg/L,且该湖泊出口附近DOC浓度为10.15mg/L.荧光指数(β:α、FI、BIX、HIX、Fn (280)、Fn (355))显示该湖泊DOM具有腐殖化程度较低及强自生源特征,类蛋白组分(Fn (280))相对浓度的空间分布上由西向东逐渐增大,而腐殖酸类组分(Fn (355))相对浓度峰值出现在入湖口与出湖口.通过PARAFAC解析出3种组分,分别为类富里酸(C1)、类色氨酸(C2)和类腐殖酸(C3),且C1、C2、C3含量分别占总组分强度21.96%、13.36%、84.21%.FRI法分析显示类蛋白物质所占比例之和(区域I+II)为49.65%,该结果说明水体已受到了人为因素影响.通过相关性分析结果显示,C1、C3与β:α、BIX呈显著负相关系(P<0.001),C2与β:α、BIX、Fn (355)呈正相关系(P<0.001).通过主成分分析与聚类分析,南漪湖上覆水中DOM在16个位点间呈现不同特征,但整体上水体中DOM来源受内源输入影响较为显著,应加强该湖泊内源释放污染物控制与管理.

Spectral characteristics of dissolved organic matter in the overlying water from Nanyi Lake

In order to investigate the spectral characteristics and the sources of dissolved organic matter (DOM) in the overlying water of the Nanyi Lake. Herein, ultraviolet-visible (UV-Vis) absorption and three-dimensional fluorescence excitation-emission matrix (EEMs) were utilized to characterize the DOM. Parallel factor analysis (PARAFAC), fluorescence regional integration, correlation analysis, principal component analysis, and cluster analysis were applied to qualitative and quantitative analysis on the DOM. Based on the absorption parameters of a (440), E₂/E₃,E₃/E₄,S_R of UV-Vis spectrum, it was found that DOM has humification and autogenesis characteristics. Moreover, E₂/E₃,E₃/E₄ and a(440) had positively correlation (P<0.01, P<0.05), and there was no significant correlation between S_R and a(440) (P>0.05). The relative molecular weight of DOM increased with increasing the humic acid concentration, but the humic acid concentration cannot be used to determine the sources of dissolved organic matter (DOM). According to the a(440) values, the average concentration of dissolved organic carbon (DOC) in the water was calculated to be 26.79mg/L, and the DOC value in the outlet area of the lake was 10.15mg/L. From the analysis of fluorescence indices (β:α, FI, BIX, HIX, Fn(280), Fn(355)), the DOM exhibited low humification and highly autochthonous characteristics. The spatial distribution of the relative concentration of protein-like components (Fn(280)) was gradually increased from west to east, but the peak values of the relative concentration of humic-like components (Fn(355)) were observed in the estuary and lake outlet. Three fluorescence components of fulvic-like, tryptophan-like and humic-like identified by PARAFAC model were named as C1, C2, C3, and the contribution of C1, C2, C3 to the total fluorescence intensity were 21.96%, 13.36%, 84.21%, respectively. The results of the FRI method showed that the sum of the proportions of protein-like substances (region I +II) was as large as 49.65%, and it was mainly related to anthropogenic activities. Certain correlation was observed between the fluorescence components and the spectral parameters, and it was found that the C1, C3 and β:α, BIX were significantly negative correlated (P<0.001). C3 and β:α, BIX, Fn (355) were positive correlated (P<0.001). Based on the principal components analysis and cluster analysis, the DOM presented different characteristics between the 16sites in the Nanyi Lake. Overall, the DOM was significantly affected by endogenous input, and the control and management of pollutants released from the lake should be strengthened.