Characterizing the interactions between trace metals and dissolved organic matter using excitation-emission matrix...

Area of Science:

• Environmental Chemistry
• Aquatic Chemistry
• Spectroscopy

Background:

• Natural dissolved organic matter (DOM) comprises diverse organic compounds.
• DOM significantly influences metal behavior in aquatic systems.
• Understanding metal-DOM interactions is crucial for environmental monitoring.

Purpose of the Study:

• To characterize interactions between DOM fluorescent components and trace metals (Cu(II), Hg(II)).
• To evaluate the efficacy of fluorescence quenching titrations coupled with EEM-PARAFAC for studying metal-DOM binding.
• To assess variations in metal-DOM interactions based on DOM composition and metal type.

Main Methods:

• Fluorescence quenching titrations were employed.
• Excitation-emission matrix (EEM) spectra were acquired.
• Parallel factor analysis (PARAFAC) was used to resolve fluorescent components and analyze metal binding.

Main Results:

• Reproducible binding interactions were observed between humic-like DOM components and Cu(II).
• Distinct differences in metal-DOM interactions were found across varying DOM compositions and between Cu(II) and Hg(II).
• Protein-like DOM components showed altered fluorescence with Cu(II) addition at mangrove sites, indicating environmental-specific molecular changes.

Conclusions:

• The combination of fluorescence quenching titrations and EEM-PARAFAC is a sensitive and reproducible method for quantifying trace metal binding with DOM components.
• This approach provides valuable insights into intermolecular DOM and DOM-trace metal interactions.
• The study highlights the importance of DOM composition in modulating metal interactions in aquatic environments.