High Voltage: The Molecular Properties of Redox-Active Dissolved Organic Matter in Northern High-Latitude Lakes

Redox-active functional groups in dissolved organic matter(DOM)are crucial for microbial electron transfer and methane emissions.However, the extent of aquatic DOM redox properties across northernhigh-latitude lakes and their relationships with DOM composition havenot been thoroughly described. We quantified electron donating capacity(EDC) and electron accepting capacity (EAC) in lake DOM from Canadato Alaska and assessed their relationships with parameters from absorbance,fluorescence, and ultrahigh resolution mass spectrometry (FT-ICR MS)analyses. EDC and EAC are strongly tied to aromaticity and negativelyrelated to aliphaticity and protein-like content. Redox-active formulaespanned a range of aromaticity, including highly unsaturated phenolicformulae, and correlated negatively with many aliphatic N and S-containingformulae. This distribution illustrates the compositional diversityof redox-sensitive functional groups and their sensitivity to ecosystemproperties such as local hydrology and residence time. Finally, wedeveloped a reducing index (RI) to predict EDC inaquatic DOM from FT-ICR MS spectra and assessed its robustness usingriverine DOM. As the hydrology of the northern high-latitudes continuesto change, we expect differences in the quantity and partitioningof EDC and EAC within these lakes, which have implications for localwater quality and methane emissions. Northern high-latitudelakes are hotspots for organic mattercycling and redox processes. This study quantifies electrochemicalproperties of dissolved organic matter from northern high-latitudelakes and describes their chemical characteristics.

Automated summary

Redox-active functional groups in dissolved organic matter (DOM) play a crucial role in microbial electron transfer and methane emissions. This study quantifies the electron donating and accepting capacities of DOM from northern high-latitude lakes and investigates their relationships with DOM composition. The results show that the redox properties of DOM are strongly tied to aromaticity and negatively related to aliphaticity and protein-like content. These findings have implications for water quality and methane emissions in these lakes.