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Zhang, C.* ; Mo, S.* ; Liu, Z.* ; Chen, B.* ; Korshin, G.* ; Hertkorn, N. ; Ni, J.* ; Yan, M.*

Interpreting pH-dependent differential UV/VIS absorbance spectra to characterize carboxylic and phenolic chromophores in natural organic matter.

Water Res. 244:120522 (2023)
DOI PMC
Open Access Green as soon as Postprint is submitted to ZB.
Natural organic matter (NOM) is critical for the biogeochemical cycles of energy and many elements in terrestrial and aquatic ecosystems, and protonation-active functional groups in NOM molecules, notably carboxylic and phenolic groups often mediate these critical environmental functions. Molecular heterogeneity, polydispersity and dynamic behavior of NOM complicate achieving an unambiguous description of its molecular properties and reactivity. This study demonstrates that differential ultraviolet-visible (UV/VIS) absorbance spectra (DAS) of NOM acquired at varying pH values exhibit several distinct features associated with the deprotonation of NOM molecules, independent of the environmental provenance of NOM (e.g., surface water, seawater, sediment, and wastewater). The protonation-active functionalities that contribute to the Gaussian distribution bands present in the DAS were identified here by comparing characteristic properties of the bands with the stoichiometries of NOM molecules ascertained by Ultrahigh-Resolution Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS). The protonation-active individual chromophores universally present in NOM molecules were identified by a genetic molecular network analysis. The observed DAS features were closely modeled via superimposing DAS spectra of 51 individual protonation-active chromophores. Molecular orbital theory was applied to further interpret the deprotonation of these chromophores, their molecular structure, electron distribution, and electron transitions measured using DAS. The high sensitivity and easy implementation of the DAS approach allows using it as a powerful tool to quantify the molecular properties and reactivity of NOM at environmental concentrations.
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Publication type Article: Journal article
Document type Scientific Article
Corresponding Author
Keywords Active Chromophores ; Differential Uv-visible Absorbance Spectra ; Genetic Molecular Network ; High Resolution Mass Spectrometry ; Natural Organic Matter (nom); Molecular Characterization; Mass-spectrometry; Environments; Persistence; Binding; Soils; Model
ISSN (print) / ISBN 0043-1354
e-ISSN 1879-2448
Journal Water Research
Quellenangaben Volume: 244, Issue: , Pages: , Article Number: 120522 Supplement: ,
Publisher Elsevier
Publishing Place Amsterdam [u.a.] ; Jena [u.a.]
Non-patent literature Publications
Reviewing status Peer reviewed
Grants Center for Life Science in Peking University
International Postdoctoral Exchange Fellowship Program
National Natural Science Foundation of China