水溶性有机物电子转移能力与荧光峰强度的关系研究

Relationship Between Electron Transfer Capacity and Fluorescence Characteristics of Dissolved Organic Matter

以不同来源的水溶性有机物(DOM)为供试材料,采用电化学方法和荧光光谱法研究了DOM电子转移能力及其与荧光峰强度的关系.采用库仑安培法测定DOM电子转移能力,其中测得的电子接受能力为635.6～1 049.3μmol.(g.C)-1,电子供给能力为27.3～42.3μmol.(g.C)-1.利用循环伏安法研究DOM电化学活性,发现其氧化还原电位在-731～-996 mV(vs.Ag/AgCl)之间.经过电位跃阶法三次氧化还原循环后电子转移能力仍可维持在232.1～897.2μmol.(g.C)-1之间,电子循环率为36.7%～78.2%,说明DOM具有重复利用、反复转移电子的特性.采用荧光激发发射光谱法(EEMS)测定DOM的类富里酸荧光峰强度并比较其与DOM电子转移能力的关系,发现DOM的类富里酸荧光峰强度与DOM的电子循环率具有显著相关(r2=0.92).实验结果为理解DOM在元素循环、污染物降解以及生物地球化学循环中的作用提供科学依据.

This study demonstrated the relationship between redox activity and fluorescence characteristics of different dissolved organic matter(DOM) employing a combined method of electrochemistry and fluorescence spectroscopy.Chronoamperometry was used to quantitatively evaluate the electron transfer capacity(ETC) of DOM.Data showed that the electron accepting capacity of DOM ranged from 635.6 μmol·(g·C)-1 to 1 049.3 μmol·(g·C)-1,and the electron donating capacity ranged from 27.3 μmol·(g·C)-1 to 42.3 μmol·(g·C)-1.For all DOM tested,the cyclic voltammetries(CVs) showed an evident pair of redox peak with the redox potentials in the range from-731 mV to-996 mV(vs.Ag/AgCl),suggesting their electrochemical activity.Using the multi-potential steps method,the ETC was measured to be 232.1-897.2 μmol·(g·C)-1 and the electron recycling rates(ERRs) were 36.7%-78.2%,indicating the electron transfer of DOM has a reversible character.Using fluorescence excitation-emission spectroscopy(EEMS),the ERRs were found to be highly correlated with the fulvic-like fluorescence intensity of DOM with a correlation coefficient of 0.92.This study can potentially provide a scientific base for understanding the roles of DOM in the elements cycles,pollutants degradation and biogeochemical cycles.