Electron Exchange Capacity of Dissolved Natural Organic Matter: Further Method Development and Interpretation using Square Wave Voltammetry in Dimethyl Sulfoxide

Abstract

Natural organic matter (NOM), including pyrogenic dissolved organic matter (pyDOM), plays an important role in mediating environmental biotic and abiotic redox reactions through its electron exchange capacity (EEC). However, the measurement and interpretation of EEC is a challenging area of current research due to the complex and variable structure of NOM. Recently, we introduced a novel approach to measuring EEC using square-wave voltammetry (SWV) in dimethyl sulfoxide (DMSO), which helped to expose a variety of validation and application issues through comparison of EECs between this and other methods. This study more-thoroughly explores several of those issues, including (i) the rationale and optimization of the method calibration and (ii) the interpretation of the large values of EEC obtained with some samples of pyDOM.