Distribution characterization and source analysis of dissolved organic matters in Taihu Lake using three dimensional fluorescence excitation-emission matrix
利用三维荧光技术分析太湖水体溶解性有机质的分布特征及来源

The distribution of dissolved organic matter (DOM) in surface (0.5 m) and bottom (1.5 m) water of Taihu Lake and possible sources were analyzed using a three-dimensional fluorescence excitation-emission matrix (3DEEM). The results indicate that proteinoid materials generally exist in the entire Taihu Lake. The concentration of humic acid and proteinoid materials is higher in Zhushan Bay. The distribution of DOM in different lake areas varies, that is, the intensity of all types of fluorescence peaks in the northern lake is generally higher than in the western, eastern, and central part of the lake, and the intensity of the fluorescence peaks in the near-shore water is higher than in the central area. DOM in the north and west part of the lake is derived from both land-sourced materials and microbial degradation, while DOM in Zhushan Bay is mainly from the landscape. DOM in Meiliang Bay and Gonghu Bay is mostly originated from microbial degradation in the lake water, and DOM in the west part of the lake is primarily from land-based substances, and in contrast, DOM in the east and center part of the Taihu Lake is mainly from microbial degradation in the water. Analyses of relationships between four types of the fluorescence peak intensity and different water quality parameters indicate that the four types of fluorescence peaks of DOM in Taihu Lake are significantly positively correlated. Also, the fluorescence intensities of the four types have a significant positive relationship with TN, TP, NO-3 and NH+4 concentration, but it presents a significantly negative correlation with dissolved oxygen. This could be explained in that a higher content of DOM would benefit reproduction of microbes and stimulate their activities, which in turn would consume a large amount of dissolved oxygen. The insignificant correlation between fluorescence intensity and DOC concentrations may be due to the proportion change in non-fluorescent substances of DOM in different lake areas.