The influence of DOM concentration, composition, and degradation transformation on carbon emissions in the inflow rivers of Lake Taihu, China

Abstract

Dissolved organic matter (DOM), characterized by its high vulnerability to degradation, is integral to riverine ecosystems and has a substantial impact on carbon emissions. However, the impacts of DOM and its degradation on carbon emissions remain unclear. This study employed a combination of meta-analysis, field sampling, and laboratory experiments to examine the effects of DOM concentration, composition, and degradation transformation on carbon emissions. Meta-analysis of literature data revealed that elevated dissolved organic carbon (DOC) concentrations in water bodies significantly increased dissolved CO₂ concentrations (cCO₂), CO₂ diffusion fluxes (FCO₂), and dissolved CH₄ concentrations (cCH₄). Field investigations in the inflow rivers of Lake Taihu, utilizing stable isotope and multi-spectral techniques, demonstrated that protein-like substances dominated the DOM composition, accounting for 74.98 ± 11.10 % of the overall fluorescence intensity. The δ¹³C-CH₄ values (−31.18 ‰ ± 3.79 ‰) indicated that acetoclastic methanogenesis was the dominant pathway. Further analysis suggested that an increase in terrestrial humic-like substances in the study area may promote carbon emissions. The DOM degradation experiment further showed that DOM degradation promoted the production of CH₄. The amount of CH₄ released through light combined with biodegradation (L-Biodegradation) exceeds that from biodegradation. In addition, the consumption of humic-like substances during DOM degradation is a crucial factor in promoting CH₄ production. This research enhances the comprehension of the relationship between DOM degradation and greenhouse gas emissions. Furthermore, it offers potential strategies for the control and mitigation of greenhouse gas emissions from riverine environments.