Characterizing Chromophoric Dissolved Organic Matter (CDOM) in Lake Chaohu in Different Hydrologic Seasons
LI Yu-yang1, 2, GUO Yan-ni2, ZHU Jun-yu2, ZHOU Lei2, 3, ZHOU Yong-qiang2, 3, HU Chun-hua1*
1. Key Laboratory of Poyang Lake Environment and Resource Utilization, Ministry of Education, School of Resources Environmental & Chemical Engineering, Nanchang University, Nanchang 330031, China
2. Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
3. University of Chinese Academy of Sciences, Beijing 100049, China
Abstract：In this paper, water samples were taken from Lake Chaohu in January (dry), April (wet-to-dry transition), and July (wet) to explore the spectral composition and distribution characteristics of chromophoric dissolved organic matter (CDOM) under different hydrologic conditions. Our results showed that there was no significant difference between the mean of dissolved organic carbon (DOC) in the wet season (3.90±0.40) mg·L-1 and in the dry season (3.89±0.19) mg·L-1. The mean spectral slope of CDOM, i. e. S275～295 in the wet season (21.48±1.56) μm-1was significantly higher than that in the dry season (19.24±0.98) μm-1 (t-test, p<0.001). Using CDOM fluorescence and parallel factor analysis, four fluorescence components were obtained including a microbial humic-like C1, a tryptophan-like C2, a tyrosine-like C3, and a terrestrial humic-like C4. C1 and C4 increased with increasing TP, TN, Chl-a, and DOC (p<0.01), and we further found a positive relationship between DOC and tryptophan-like C2 (p<0.05). There were seasonal differences in the optical component and sources of CDOM in Chaohu. In the wet season, terrestrial humic-rich CDOM contributed primarily while in the wet-to-dry transition season, autochthonous CDOM derived from algal degradation contributed to the lake’s CDOM pool. In order to protect the water quality of the lake effectively, certain control measures should be carried out in the watersheds of the Shiwuli River and the Nanfei River.
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