Coupling electrooxidation-coagulation with membrane distillation using recycled Al can cathodes for sustainable landfill leachate treatment: Fouling control and mechanism insights.

Chemically recalcitrant molecules are the primary components regulating the electron-donating capacity (EDC) of dissolved organic matter.

Sources and mineralization determine the generation and transformation pathway of sedimentary organic matter over the past century.

Benthic biofilms as reservoirs of recalcitrant organic matter in freshwater reservoirs: insights from FT-ICR MS.

Unraveling the mechanism of dissolved organic matter in enhancing nitrogen removal from leachate wastewater treatment via aerobic granular sludge process.

Molecular-scale investigation on the role of MnO2-mediated oxidation in regulating photochemical reactivity of dissolved organic matter.

Extreme precipitation amplified the cumulative effects of DOM availability on organic-sourced DIC in the Yangtze River.

Dissolved organic matter (DOM) is a crucial carbon source for soil microorganisms and plays a vital role in nutrient cycling and carbon (C) sequestration in soils. However, the extent to which soil microbes mediate DOM transformation at the molecular level, and whether this is regulated by different organic fertilization, remains unclear. Here, we designed a field experiment to investigate the transformations of DOM under three types of organic fertilization (straw, biochar, and manure) using Fourier transform ion cyclotron resonance mass spectrometry and metagenomic analysis. Compared to the control, manure fertilization increased the molecular chemodiversity of DOM by 33.2%, with recalcitrant compounds (e.g., highly unsaturated phenolic compounds and lignins) increasing by 47.2%. In contrast, labile compounds (e.g., aliphatics) decreased by 73.5%. Compared to straw treatment, manure application significantly increased the average conversion rate of dissolved organic matter (DOM). This process was accompanied by a significant increase in the Shannon index of the soil microbial community (p < 0.05) and upregulation of ABC transporter-encoding genes (e.g., livK, livM). DOM composition directly governed transformation potential (p < 0.01), whereas functional genes enhanced transformation indirectly by modulating DOM composition. This study elucidates microbial-mediated DOM transformation mechanisms under varying organic fertilization practices, providing a scientific basis for optimizing soil organic matter management in paddy ecosystems.

Dissolved organic matter (DOM) plays a key role in influencing the environmental behavior of heavy metals in lake ecosystems. Through mechanisms such as complexation, ion exchange, and physical adsorption, DOM regulates the speciation, transport, and bioavailability of heavy metals, thereby shaping their ecological risks and fate. Here, we provide a comprehensive review of the sources and molecular composition of lake DOM, with particular attention to humic substances, proteins, and polysaccharides, and highlight the importance of functional groups such as carboxyl group and phenolic hydroxyl group in metal binding. The mechanisms of DOM-heavy metal interactions are discussed in detail. These include σ-ligand bonding, which relies on the donation of lone pair electrons from O/N-containing functional groups to metal orbitals. Also covered are π-d electron interactions, often initiated by photoexcitation of aromatic moieties in DOM to facilitate electron transfer, and multi-site adsorption, a process governed by the combined effects of electrostatic attraction, hydrogen bonding, and the porous structure of DOM. Additionally, the effects of environmental factors (temperature, pH, and light) and biological factors (microbial activity and aquatic plant decomposition) on DOM-heavy metal dynamics are examined. Although substantial progress has been made, key challenges remain in understanding the microscale mechanisms, capturing real-time changes in natural waters, and assessing long-term ecological impacts. Future research should prioritize multi-scale approaches. This entails employing advanced techniques like Fourier-transform ion cyclotron resonance mass spectrometry to elucidate molecular mechanisms, while also advancing in situ monitoring technologies and establishing long-term observation networks to resolve real-time dynamics and assess cumulative ecological impacts. This review provides a theoretical basis for understanding DOM-heavy metal interactions and supports future efforts in ecological risk assessment and the sustainable management of lake environments.

Microplastic-derived dissolved organic matter (MP-DOM) has attracted widespread attention due to their adverse effects on ecological health. However, the dynamic formation of MP-DOM at molecular level is not yet fully understood. Herein, the molecular level formation characteristics and mechanism of polyamide-microplastic-derived dissolved organic matter (MPPA-DOM) during irradiation were explored using fluorescence spectroscopy. Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS), and parallel factor analysis (PARAFAC). The results showed that the time-dependent fluorescence signatures revealed a dominant tyrosine-like component whose relative abundance increased from 49.63% to 89.62% during irradiation, suggesting a gradual accumulation of protein-related substances. Molecular element analyses of MPPA-DOM revealed the predominance of CHON molecules (78.82%-89.30%), which was attributed to the degradation of the C-N backbone structure. In contrast, CHO molecules exhibited a lower proportion (9.45%) under prolonged irradiation. Aliphatic/peptide-like compounds in MPPA-DOM remained the dominant component with percentage range of 66.4%-68.7%, while lignin-like compounds slightly increased with the increase of irradiation time. The reduced molecules were dominated in MPPA-DOM with percentage range of 96.4%-99.1%. As irradiation increased, the saturated compounds decreased from 91.53% to 82.45% and the unsaturated compounds increased from 7.6% to 14.1%. This study proposed a molecular-level formation mechanism of MPPA-DOM under irradiation. Nitrogen-rich molecules were persistent and highly stable during irradiation, indicating that they could play a more important role in the migration and transformation of MPPA-DOM. The findings in this study will provide support for assessing the potential ecological risks of MP-DOM in water systems.

Dissolved organic matter (DOM) plays an important role in microbial electron transfer, influencing elemental biogeochemical cycles and pollutant fate. However, its electron exchange capacity (EEC) can be strongly altered by ferrous {Fe(II)} oxidation-driven adsorptive fractionation and chemical transformations under long-term periodic hydrological fluctuations, which remain largely unexplored. Here, we demonstrate that periodic Fe(II) oxidation progressively increases DOM's EEC by up to 6.2-fold. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis revealed that Fe(II) oxidation increased the low-molecular-weight polyphenolic and highly unsaturated phenolic fractions of DOM by 26.3 and 24.4%, respectively, and enriched quinone and phenolic groups that can mediate electron transfer. Meanwhile, integration of FT-ICR MS data with machine learning identified the changes in molecular weight and O/C ratio as the critical characteristics determining the enhanced EEC of DOM, with newly produced sulfur-containing groups contributing thereafter. Both adsorptive fractionation and reactive oxygen species-triggered oxidative transformation during Fe(II) oxidation determined the increased EEC of DOM, with adsorptive fractionation playing the dominant role. These dynamic DOM changes significantly promoted microbial electron transfer, continuously stimulating iron reduction and concurrent arsenic release in paddy soils, thereby potentially exacerbating toxic metal bioavailability and posing risks to food safety.

Deciphering the composition and degradation of dissolved organic matter in a large subtropical river using optical indices and high-resolution FT-ICR-MS.

Trade-offs in microplastic-adsorbed iopamidol degradation by UV-AOPs: Molecular-level insights into deiodination pathways versus iodinated disinfection by-products formation.

Understanding the elemental and structural composition of mercury-dissolved organic matter (Hg-DOM) complexes is crucial for comprehending Hg speciation, bioavailability, and transformations in aquatic ecosystems. However, low concentrations of these organo-metal complexes in natural waters and extraction at acidic pH constrain their characterization. Here, we used solid phase extraction (SPE) methodology to extract Hg-DOM complexes at ambient pH and validated their preconcentration by preserving the composition for identification using ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). While the dissolved organic carbon (DOC) extraction efficiency was higher with cartridges containing styrene divinylbenzene copolymer (PPL) than silica structure bonded with hydrocarbon chains (C18), Hg in both extracts showed no significant difference. FT-ICR-MS analysis revealed that Hg-DOM complexes extracted by C18 cartridges were aliphatic with smaller carbon chains (16-18), whereas complexes extracted with PPL exhibited both aliphatic and aromatic characteristics with a wide distribution of carbon chains ranging from 17 to 25. TheC18 cartridge appeared to be selective in extracting and preserving the nonpolar complexes, asevidenced by the identification of two molecular formulae, C16H31HgNO3 and C16H35HgNO2S, with m/z ratios of 487.2 and 507.21, across triplicate extractions. This study addresses the challenge of the spectroscopic limitation of Hg-DOM identification by extracting these complexes at circumneutral pH and presumably preserving them from dissociation during extraction.

Effective control disinfection byproducts in municipal wastewater by UV-based advanced oxidation/reduction pre-treatments: Insights from FT-ICR-MS analysis.

Differential aging processes of microplastics in paddy soil under wet-dry alternation: Insights into chemical structure alteration and dissolved organic matter formation.

Methane biogeochemical turnover constrains arsenic transformation in groundwater systems: Organic molecular signatures and microbial functional networks.

Polycyclic nitroaromatic compounds in HULIS as dominant pro-apoptotic agents in PM2.5: Biomass/coal combustion sources, structural insights, and biomarker discovery.

Pyrolysis of nitrogen-rich microalgae: kinetics, products, and amino acid contributions.

Changes in dissolved organic matter chemistry of plateau lakes along gradients of human activity intensity in Yunnan Province, China.