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

Abstract

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 northern high-latitude lakes and their relationships with DOM composition have not been thoroughly described. We quantified electron donating capacity (EDC) and electron accepting capacity (EAC) in lake DOM from Canada to 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 negatively related to aliphaticity and protein-like content. Redox-active formulae spanned a range of aromaticity, including highly unsaturated phenolic formulae, and correlated negatively with many aliphatic N and S-containing formulae. This distribution illustrates the compositional diversity of redox-sensitive functional groups and their sensitivity to ecosystem properties such as local hydrology and residence time. Finally, we developed a reducing index (RI) to predict EDC in aquatic DOM from FT-ICR MS spectra and assessed its robustness using riverine DOM. As the hydrology of the northern high-latitudes continues to change, we expect differences in the quantity and partitioning of EDC and EAC within these lakes, which have implications for local water quality and methane emissions.

Electron Donating Capacity: A Promising Surrogate Indicator for the Optimization of Oxidative Water Treatments

“…For samples with a DOC concentration beyond this range, serially diluted samples should be tested to determine the optimal DOC concentration for EDC analysis (Text S2). ,, …”

Thermal responses of dissolved organic matter under global change

“…The intrinsic temperature sensitivity of reaction rates is increased at lower temperatures making soil carbon potentially more vulnerable to decomposition at higher latitudes under future climate change 13 , 14 , while there are higher vulnerability in decomposition at both high and low latitudes as indicated by H/C ratio of DOM in aquatic ecosystem 15 . The observed “apparent” temperature sensitivity of decomposition therefore reflects a combination of the intrinsic traits (e.g., bioavailability) of organic compounds and environmental constraints 13 , 16 , which can also be affected by other global change drivers, especially nutrient enrichment 17 , 18 in additive or multiplicative ways.…”

Effect of Dissolved Organic Matter on the Photodegradation of Decachlorobiphenyl (PCB-209) in Heterogeneous Systems: Experimental Analysis and Excited-State Theory Calculations

“…Dissolved organic matter (DOM), as a component of natural waters, plays a critical role in the storage and transport of contaminants through adsorption, altered bioavailability, etc. − Meanwhile, DOM also affects photoreactions and redox reactions in water bodies. − As a photosensitizer, DOM contains a large number of chromophores and is a major source of photochemically generated reactive intermediates such as excited triplet-state DOM ( 3 DOM*) and reactive oxygen species [ROS, i.e., hydroxyl radical ( • OH), singlet oxygen ( 1 O 2 ), superoxide anion free radical ( • O 2 – )] − that can react with contaminants. However, the absorption of photons may lead to the so-called light-shielding effect that can adversely affect the direct photodegradation of contaminants .…”