Probing Molecular-Level Dynamic Interactions of Dissolved Organic Matter with Iron Oxyhydroxide via a Coupled Microfluidic Reactor and an Online High-Resolution Mass Spectrometry System.
Environ Sci Technol
; 57(7): 2981-2991, 2023 02 21.
Article
em En
| MEDLINE
| ID: mdl-36749182
ABSTRACT
The interactions between dissolved organic matter (DOM) and iron (Fe) oxyhydroxide are crucial in regulating the biogeochemical cycling of nutrients and elements, including the preservation of carbon in soils. The mechanisms of DOM molecular assembly on mineral surfaces have been extensively studied at the mesoscale with equilibrium experiments, yet the molecular-level evolution of the DOM-mineral interface under dynamic interaction conditions is not fully understood. Here, we designed a microfluidic reactor coupled with an online solid phase extraction (SPE)-LC-QTOF MS system to continually monitor the changes in DOM composition during flowing contact with Fe oxyhydroxide at circumneutral pH, which simulates soil minerals interacting with constant DOM input. Time-series UV-visible absorption spectra and mass spectrometry data showed that after aromatic DOM moieties were first preferentially sequestered by the pristine Fe oxyhydroxide surface, the adsorption of nonaromatic DOM molecules with greater hydrophobicity, lower acidity, and lower molecular weights (<400) from new DOM solutions was favored. This is accompanied by a transition from mineral surface chemistry-dominated adsorption to organic-organic interaction-dominated adsorption. These findings provide direct molecular-level evidence to the zonal model of DOM assembly on mineral surfaces by taking the dynamics of interfacial interactions into consideration. This study also shows that coupled microfluidics and online high-resolution mass spectrometry (HRMS) system is a promising experimental platform for probing microscale environmental carbon dynamics by integrating in situ reactions, sample pretreatment, and automatic analysis.
Palavras-chave
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Microfluídica
/
Matéria Orgânica Dissolvida
Tipo de estudo:
Prognostic_studies
Idioma:
En
Revista:
Environ Sci Technol
Ano de publicação:
2023
Tipo de documento:
Article
País de afiliação:
China