利用三维荧光光谱和紫外-可见光谱技术,通过室内模拟实验研究了光照对洱海上覆水溶解性有机氮(DON)影响,经平行因子分析法(PARAFAC)和荧光区域积分法(FRI)解析了DON含量、结构组分变化特征,并探讨了其环境学意义.结果表明:(1)未加汞光照条件下,洱海上覆水DON含量随光照时间延长呈波动上升趋势,NH4+与DON含量呈显著负相关(R2=0.94,P＜0.05),即NH4与DON之间存在相互转化,且光照可能促进了NH4向DON的转化;(2)加HgCl2后实验组与对照组SUVA254(1.78、1.85)、A253/A203(0.35、0.34)、E2/ E3(5.85、5.77)及SR(1.03、1.14)均值差别不大,未加HgCl2实验组较对照组SUVA254、A253/A203、Ez/E3值有一定差别,表明光照主要是通过微生物作用,进而影响DON特征,表现为光照增强了DON芳香环取代基结构的复杂程度,并且使得羰基、羧基、羟基和酯基种类有所增多;(3) PARAFAC识别出类蛋白质物质(T峰)和类富里酸物质(A峰)两类组分,表明腐殖质类物质与蛋白质类物质之间可能存在相互转化,且微生物所发挥的作用较为明显.以上结果表明,光照可增强生物活性,进而影响对DON的转化和降解.
Indoor simulation experiments were conducted to investigate the dissolved organic nitrogen (DON) concentrations in the overlying water from Lake Erhai by 3D fluorescence and ultravioletvisible spectroscopy techniques.Characteristics of DON content,structure and component were analyzed by parallel factor method (PARAFAC) and fluorescence area integral method,and the environmental significance was also discussed in detail in this study.Results indicated that:(1) in the absence of HgC12,DON content showed a rising but fluctuating trend with illumination time.NH4+ and DON contents were significantly negative correlated (R2=0.94,P ＜ 0.05),suggesting a possible mutual conversion between NH4+ and DON.This suggests that illumination might promote the transformation of NH4+ to DON.(2) The mean values of SUVA254 (1.78,1.85),A253/A203 (0.35,0.34),E2/E3(5.85,5.77) and SR(1.03,1.14) in the experimental group and control group were similar when HgCl2 was added.But without HgCl2,the values were slightly different,which was characterized by the enhanced DON substituent aromatic ring structure complexity under light condition.And correspondingly,the carbonyl and carboxyl,hydroxyl and ester base types increased.(3) PARAFAC identified two types of components,namely protein type (peak T) and fulvic acid type (peak A).Potential transformation between humic substances and protein existed,during which microbes played an important role.Both point (2) and (3) demonstrated that light could enhance biological activity and further affect the transformation and degradation of DON.
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