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

利用三维荧光光谱法研究了太湖125个样点表层(0.5m)和底层(1.5m)水体溶解性有机质(DOM)的组成和分布特征,并对不同湖区DOM的来源进行了分析.结果表明,太湖大部分湖区水体DOM以类蛋白物质为主,其中,竺山湾DOM中的腐殖质和类蛋白物质含量均较其它湖区高.太湖水体DOM的分布存在区域差异性,即:竺山湾湖区西部湖区梅梁湾湖心区贡湖湾南部湖区.分析认为,太湖DOM的来源具有陆源输入与内源微生物降解的双重特征,但竺山湾和西部湖区以陆源输入为主,而梅梁湾、贡湖、南部湖区及湖心区以内源微生物降解为主.分析各类荧光峰强度与水质参数的相关性发现,太湖水体DOM4类荧光峰之间呈显著正相关关系,DOM的4类荧光峰均与总氮(TN)、总磷(TP)、硝酸根离子(NO3-)、铵根离子(NH4+)呈显著正相关关系(p0.01),DOM的各类荧光峰强度和溶解氧呈显著负相关(p0.01),这可能是由于水体DOM含量升高后,微生物比较活跃,消耗大量的溶解氧所致;DOM的各类荧光峰强度和溶解性有机碳(DOC)之间的相关性不显著,可能与不同湖区样品中一些非荧光物质在DOM中的比例不同有关.

Distribution characterization and source analysis of dissolved organic matters in Taihu Lake using three dimensional fluorescence excitation-emission matrix

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.