Effect of Sunlight Irradiation on Fluorescence Properties of Dissolved Organic Matter
FU Ping-qing1, 2,WU Feng-chang1*,LIU Cong-qiang1,XU Cheng1, WANG Jing1, 2,BAI Ying-chen1, 2,WANG Li-ying1, 2
1. The State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China 2. Graduate School of the Chinese Academy of Sciences, Beijing 100039, China
Abstract：Three-dimensional excitation emission matrix fluorescence spectroscopy (3DEEM) was used to investigate the effect of sunlight irradiation on the fluorescence properties of dissolved organic matter (DOM) from Lake Hongfeng and Nanming River waters and a commercial fluka humic acid (FHA). The results show that the DOM samples and FHA fluorescence properties changed under sunlight irradiation. Interestingly, the photodegradation characteristics were different between aquatic DOM and FHA. The fluorescence intensity of the apparent peaks A, B and C of lake and river water DOM decreased with sunlight irradiation. The initial 3DEEM of Fluka HA had only one fluorescence peak at λex/λem=275/500 nm, while two fluorescence peaks occurred at λex/λem=245/450 nm and 310/450 nm, respectively, after sunlight irradiation. λex and λem maxima of DOM decreased during 7 days of sunlight irradiation. Changes in r(A, C) of DOM and FHA with sunlight irradiation time suggest that fluorescence peaks A and C had different fluorescence loss rates, while peak C fluorophores were more susceptible to sunlight irradiation. FHA appeared to be less susceptible to photodegradation，and its r(A, C) remained almost the same before and after sunlight irradiation.
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