Just Accepted

This article has been peer reviewed and accepted for publication. It is in production and has not been edited, so may differ from the final published form.

Variations in hydrogen peroxide (H2O2) concentration are influenced by the sources of dissolved organic matter (DOM) in tropical and subtropical aquatic environments

Patricia Garcia , Haruka Urakawa, Taylor Hancock, Hidetoshi Urakawa

Abstract

Rationality Dissolved organic matter (DOM) is a complex mixture of compounds that is ubiquitous in aquatic ecosystems and is involved in multiple biogeochemical processes. The lysis of DOM due to exposure to solar radiation can produce reactive photoproducts. Among these, reactive oxygen species (ROS), particularly hydrogen peroxide (H2O2), are strong oxidant agents. We aim to expand our understanding of the complex relationship between DOM and H2O2 in tropical and subtropical aquatic systems in Florida. Methodology Using absorbance and fluorescence-based methods, we characterized the DOM quality. Additionally, we measured the H2O2 concentrations in 42 aquatic systems. Results The freshwater aquatic ecosystems showed a broad variation in DOM quantity and quality. Based on their origin, the water samples can be grouped int three categories: autochthonous, recently produced allochthonous and allochthonous DOM. Using parallel factor analysis modeling (PARAFAC), we validated five fluorescent components: three humic like components, one fulvic component and one protein-like component. Notably, the humic-like component C4 (A), autochthonous and fresh allochthonous DOM, showed a significant direct relationship with H2O2 concentrations. Conversely, in water bodies primarily characterized by allochthonous DOM origin, a significant direct linear relationship was observed between chlorophyl a and H2O2 concentrations. Discussion Overall, our results support the idea that reactive humic compounds serve as a primary substrate for H2O2 production, however, in the absence of reactive compounds, the biological processes also play a crucial role in the H2O2 production.

EN25005  Accepted 27 August 2025

© CSIRO 2025