铜绿微囊藻胞内DOM光降解及其对芘结合能力的影响

利用紫外可见吸收光谱法及荧光光谱法研究有氧和缺氧条件下紫外线A波段(UV-A)辐照对铜绿微囊藻(Microcystis aeruginosa)胞内溶解性有机质(IDOM)(M. aeruginosa-IDOM)光降解行为,并考察光降解对其与芘结合能力的影响.结果表明,M. aeruginosa-IDOM经6d光降解后,有氧组中溶解性有机碳(DOC)浓度及其吸收系数a₃₅₅降解幅度均高于缺氧组.有氧及缺氧状态下M. aeruginosa-IDOM光降解过程中吸光度比值E2/E3(250nm/365nm)变化相似,但254nm处比紫外吸收值(SUVA₂₅₄)变化不同.激发–发射三维荧光光谱法(EEMs)结合平行因子(PARAFAC)分析,结果显示, M. aeruginosa-IDOM中类蛋白C1、长波激发类腐殖质C2及短波激发类腐殖质C3荧光强度在两种光降解条件下变化趋势不同. M. aeruginosa-IDOM光降解过程符合一级降解动力学特征的参数,在有氧组中降解半衰期均短于缺氧组.此外,光降解过程中,有氧组M. aeruginosa-IDOM与芘结合能力降低,但缺氧组M. aeruginosa-IDOM与芘结合能力先下降后增加.

Photodegradation of intracellular DOM from Microcystis aeruginosa and its effect on the binding of pyrene

UV-visible spectroscopy and fluorescence spectroscopy were applied to study the photodegradation of intracellular dissolved organic matter (IDOM) from Microcystis aeruginosa (M. aeruginosa-IDOM) upon ultraviolet A (UV-A) irradiation under oxic and anoxic conditions. Furthermore, the binding affinity of pyrene with the M. aeruginosa- IDOM was investigated by fluorescence quenching method throughout the process of photodegradation. After 6 d irradiation, the reduction of dissolved organic carbon (DOC) and absorption coefficient a₃₅₅ under oxic condition were larger than those under anoxic condition. The variations of absorbance ratio E2/E3 (250nm/365nm) for oxic and anoxic photodegradation were similar. However, the variations of specific ultraviolet absorbance at 254nm (SUVA₂₅₄) were strikingly different. Fluorescence excitation-emission matrix spectroscopy (EEMs) combined with parallel factor (PARAFAC) analysis showed that the changes in protein-like component, long-wavelength-excited humic-like component and short-wavelength-excited humic-like component were different for the two cases. The half-lives of photodegradation kinetics parameters of the M. aeruginosa-IDOM under oxic condition, which could be described using the first-order kinetics equation, were shorter than those parameters of anoxic condition. In addition, the affinity of the M. aeruginosa-IDOM for binding pyrene decreased under oxic condition, while first decreasing and later increasing trend was observed for pyrene binding affinity under anoxic condition.