Influence of dissolved organic matter origin on hydrogen peroxide concentration in aquatic environments of southern Florida

Abstract

Rationale. Dissolved organic matter (DOM) is a complex mixture of compounds that is ubiquitous in aquatic ecosystems and is involved in multiple biogeochemical processes. The degradation of DOM due to exposure to solar radiation can produce reactive photoproducts. Amongthese, reactive oxygen species (ROS), particularly hydrogen peroxide (H2O2), are strong oxidizingagents. We aim to expand our understanding of the complex relationship between DOM andH2O2 in tropical and subtropical aquatic systems in Florida. Methodology. Using absorbance andfluorescence-based methods, we characterized the DOM quality. Additionally, we measuredH2O2 concentrations in 42 aquatic systems. Results. Freshwater aquatic ecosystems showed abroad variation in DOM quantity and quality. Based on their origin, the water samples can begrouped int three categories: autochthonous, recently produced allochthonous and allochthonous DOM. Using parallel factor analysis modeling (PARAFAC), we validated five fluorescentcomponents: 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 bodiesprimarily characterized by allochthonous DOM origin, a significant direct linear relationship wasobserved between chlorophyll-a and H2O2 concentrations. Discussion. Overall, our resultssupport 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 crucialrole in the H2O2 production.