Zhang Qiao-Ying, Sun Wei, Du Ying-Xun, Gong Xiao-Li
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
University of Chinese Academy of Science, Beijing 100049, China.
Huan Jing Ke Xue. 2021 Apr 8;42(4):1870-1878. doi: 10.13227/j.hjkx.202007227.
A large amount of intracellular dissolved organic matter (I-DOM) is released during the senescent phase of phytoplankton cultures. This research investigated the bio-incubation of I-DOM of cyanobacteria in Lake Taihu under various temperatures (20, 25, and 30℃) and I-DOM initial concentrations (5, 10, and 20 mg·L) with the aid of ultraviolet-visible spectroscopy (UV-Vis) and three-dimensional fluorescence matrix-parallel factor (EEM-PARAFAC). I-DOM was effectively degraded during the incubation. After 14 days, the DOC removal ratio was 50% ~74%. A tryptophan-like component (C1), a ubiquitous humic-like component (C2), and two microbially-derived humic-like components (C3 and C4) contributed 80.0%, 16.0%, 3.7%, and 0.3% to the initial I-DOM, respectively. During the bio-degradation, these components are not only consumed but also produced. C1 decreased during the incubation, while C3 and C4 increased at the beginning of biodegradation and then decreased. The change trend of C2 was complicated, i.e., it decreased firstly and then increased, but decreased again after 7 days. The changes in the optical indices of , : and HIX revealed that the molecular weight of DOM increased, and the aromaticity was enhanced during degradation. The reaction temperature and the initial concentration of I-DOM did not change the trend of the PARAFAC components. The temperature of 25℃ was the most suitable for I-DOM bio-degradation. Additionally, the degradation of I-DOM was enhanced with the increase in the initial concentration of I-DOM. Combined with our study on the photodegradation of I-DOM, the possible fate of I-DOM in Lake Taihu was proposed. The tryptophan-like compound could be effectively degraded, while the humic-like components could not be degraded completely. These humic-like components would potentially settle through adsorption or coprecipitation with metal substances. These results are helpful to understand the fate of I-DOM released by a cyanobacteria bloom in Lake Taihu.
在浮游植物培养的衰老阶段会释放大量细胞内溶解有机物（I-DOM）。本研究借助紫外可见光谱（UV-Vis）和三维荧光矩阵平行因子分析（EEM-PARAFAC），研究了太湖蓝藻I-DOM在不同温度（20、25和30℃）及I-DOM初始浓度（5、10和20mg·L）下的生物培养情况。培养过程中I-DOM被有效降解。14天后，溶解性有机碳（DOC）去除率为50%~74%。一种类色氨酸组分（C1）、一种普遍存在的类腐殖质组分（C2）以及两种微生物源类腐殖质组分（C3和C4）分别对初始I-DOM的贡献为80.0%、16.0%、3.7%和0.3%。在生物降解过程中，这些组分不仅被消耗，同时也在产生。C1在培养过程中减少，而C3和C4在生物降解开始时增加，随后减少。C2的变化趋势较为复杂，即先减少后增加，但7天后又再次减少。、和腐殖化指数（HIX）的光学指标变化表明，降解过程中DOM的分子量增加，芳香性增强。反应温度和I-DOM初始浓度并未改变PARAFAC组分的变化趋势。25℃是I-DOM生物降解的最适宜温度。此外，I-DOM的降解随着I-DOM初始浓度的增加而增强。结合我们对I-DOM光降解的研究，提出了太湖I-DOM的可能归宿。类色氨酸化合物可被有效降解，而类腐殖质组分不能被完全降解。这些类腐殖质组分可能通过与金属物质的吸附或共沉淀作用沉降。这些结果有助于了解太湖蓝藻水华释放的I-DOM的归宿。
