River ecosystems receive a large amount of organic matter, which will increase the production of greenhouse gases (GHGs), including carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O). Despite extensive research on the distribution of greenhouse gases and dissolved organic matter (DOM), little is known about the associations between greenhouse gases and DOM compositions. In this study, the distributions of GHGs (CO₂, CH₄ and N₂O) and DOM in the overlying water of the main rivers around Taihu Lake were investigated. The results showed that the concentration of GHGs was positively correlated with dissolved organic carbon concentrations. Three-dimensional excitation-emission matrix fluorescence spectroscopy techniques were employed to identify the source of the DOM, which was related to protein-like and humic-like components. The DOM was a combination of terrigenous and endogenous origins. The GHGs (except CO₂) were significantly associated with DOM composition. These results emphasize the importance of the relationship between GHGs (CO₂, CH₄ and N₂O) and DOM compositions in river ecosystems.

Geopolymer is a sustainable low-carbon cementitious material that is able to incorporate large amounts of solid waste as precursors or activators. As the proportion of municipal solid waste incineration continues to rise in China, the large-scale generation of municipal solid waste incineration fly ash (MSWI FA) has emerged as a significant challenge. The production of geopolymers represents a potential pathway for the comprehensive utilization of MSWI FA. However, most studies have reported that geopolymers containing MSWI FA exhibit low strength, which diminishes their economic value. Furthermore, the unclear environmental risks associated with MSWI FA-based geopolymers have impeded their broader application. This study explores the use of MSWI FA as a substitute for ground granulated blast furnace slag (GGBS) or coal fly ash (CFA) in the production of high-performance geopolymers, achieving compressive strengths exceeding 60 MPa, even when the MSWI FA content reaches 50%. A synergistic effect is observed between MSWI FA and CFA, which enhances the reactivity of CFA. With reasonable formulation, the environmental risks of geopolymers containing MSWI FA are manageable in normal rainfall scenarios. However, there remains a potential risk of soil and groundwater contamination under extreme conditions, such as acid rain.