湖泊草源DOM与磺胺二甲基嘧啶的荧光猝灭研究

Characterizing the Interaction of Sulfamethazine and Macrophytes-derived Dissolved Organic Matter by Fluorescence Spectroscopy

磺胺二甲基嘧啶(SMT)作为一种常见的磺胺类抗生素,在富营养化湖泊中的迁移和归趋与溶解性有机质(DOM)密切相关。该研究采用荧光猝灭光谱法研究马来眼子菜释放的DOM与SMT的相互作用。同步荧光光谱和紫外可见吸收光谱表明SMT可引起DOM的构象变化,静态猝灭是主要机制。通过三维荧光光谱结合平行因子分析将DOM分为4个独立荧光组分,并结合Ryan-Weber非线性模型分析各组分与SMT的结合能力。模型拟合度较高,结合稳定常数(logK_b)大小顺序为类酪氨酸(7.22)>类色氨酸(5.54)>小分子类腐殖(5.04)>大分子类腐殖组分(无猝灭),说明DOM对SMT的络合作用较强。二维相关图谱显示类酪氨酸荧光团优先于类色氨酸荧光团与SMT发生反应。草源DOM与SMT之间的相互作用可影响SMT在富营养化湖泊中的生物有效性和毒性等环境行为。

The fate and transport of sulfamethazine （SMT）, a widely used sulfonamide antibiotics, in eutrophic freshwater lakes is significantly influenced by the ubiquitous presence of derived dissolved organic matter （DOM）. In this study, fluores- cence quenching titration was applied to study complexation of SMT to DOM. Synchronous fluorescence spectra and UV-Visible absorbance spectra revealed that DOM underwent conformation changes upon interaction with SMT and the main mechanism was attributed to static quenching. Fluorescence excitation and emission matrix （EEM） and parallel factor analysis （PARAFAC） were employed and four individual fluorescent components were identified. Their conditional stability constants （logKb） obtained by Ryan-Weber equation were in the order of tyrosine- （7.22） 〉 tryptophan- （5.54） 〉 small humic -（5.04） 〉 large humic-like （no effective quenching） components, indicating that SMT was strongly bound to DOM. Furthermore, the binding order of SMT to protein-like fluorophores in DOM was analyzed by 2D-COS, with the sequence of tyrosine-like flu- orophore 〉 tryptophan-like fluorophore. The strong interaction between SMT and macrophytes-derived DOM can affect the environmental fate of antibiotics in eutrophic freshwater lakes and may eventually change their bioavailability and toxicity to organisms.