This study examined effects of aquatic and soil natural organic matter (NOM) exemplified by standard Suwannee River fulvic acid (SRFA) and Pahokee Peat fulvic acid (PPFA), respectively, on the electrochemical (EC) reactivity and mass transfer properties of the cationic organic probe toluidine blue (TB) that forms complexes with NOM. EC measurements that were carried out using the method of rotating ring-disc electrode (RRDE) showed that for disc potentials below −0.4 V vs. the standard Ag/AgCl reference electrode, TB molecules undergo EC reduction accompanied by the formation of EC-active products that undergo oxidation at the ring electrode. EC reactions of TB in the range of potentials −0.2 to −0.4 V were determined to involve free TB⁺ cations and TB species adsorbed on the electrode surface. The EC reduction of TB species at the disc potentials < −0.4 V was controlled by the mass transfer of the free TB⁺ cations and TB/NOM complexes to the electrode surface. Formation of TB/NOM complexes caused the mass transfer-controlled TB currents to undergo a consistent decrease. The observed changes were correlated with the extent of TB/NOM complexation and decreases of the diffusion coefficients of TB/NOM complexes that have higher molecular weights (MW) than the free cations. Properties of the intermediates formed upon the reduction of TB⁺ cations were also affected by NOM. These results demonstrate that RRDE measurements of EC reactions of TB or possibly other EC active probes allow probing the complexation of EC-active organic species with NOM and mass transfer properties of NOM complexes and ultimately NOM itself.

这项研究研究了分别以标准Suwannee River黄腐酸（SRFA）和Pahokee泥炭黄腐酸（PPFA）为例的水生和土壤天然有机物（NOM）对阳离子有机物的电化学（EC）反应性和传质性能的影响探针与NOM形成复合物的甲苯胺蓝（TB）。使用旋转圆盘电极（RRDE）方法进行的EC测量表明，相对于标准Ag / AgCl参比电极，相对于低于-0.4 V的盘电位，TB分子会发生EC还原并形成EC活性物质在环形电极上发生氧化的产品。TB在电位-0.2至-0.4 V范围内的EC反应被确定为涉及游离TB ⁺阳离子和TB物质吸附在电极表面。圆盘电位<-0.4 V时TB物质的EC减少是由游离TB ⁺阳离子和TB / NOM络合物向电极表面的质量转移控制的。TB / NOM配合物的形成导致传质控制的TB电流持续下降。观察到的变化与TB / NOM络合物的程度和分子量（MW）高于游离阳离子的TB / NOM络合物的扩散系数降低相关。TB ⁺减少时形成的中间体的性质阳离子也受NOM影响。这些结果表明，对TB或可能的其他EC活性探针的EC反应进行RRDE测量，可以探测EC活性有机物与NOM的络合以及NOM配合物以及最终NOM本身的传质特性。