Photochemistry Illuminates Ubiquitous Organic Matter Fluorescence Spectra.

Area of Science:

• Environmental Chemistry
• Aquatic Biogeochemistry
• Spectroscopy

Background:

• Dissolved organic matter (DOM) represents a significant carbon reservoir in aquatic systems, crucial for global carbon budgets and water treatment.
• Current fluorescence spectroscopy methods struggle to isolate specific DOM fractions with predictable spectral characteristics.

Purpose of the Study:

• To develop a method for mathematically isolating and characterizing specific fluorescent fractions of DOM.
• To assess the spectral properties, stability, and photodegradation behaviors of these DOM fractions across different aquatic environments.

Main Methods:

• Utilized parallel factor analysis (PARAFAC) to analyze fluorescence data from lake, river, and ocean samples.
• Investigated the impact of sample extraction and photobleaching on DOM fluorescence spectra.
• Examined spectral properties and photodegradation across environmental pH gradients.

Main Results:

• Successfully isolated four ubiquitous visible-wavelength fluorescent DOM fractions with stable spectral properties.
• Demonstrated that PARAFAC components remained consistent despite changes in bulk fluorescence due to sample extraction.
• Observed preferential removal of longer-wavelength components during photobleaching.

Conclusions:

• The identified PARAFAC components provide stable spectral fingerprints for DOM fractions.
• These findings enhance the interpretation of DOM fluorescence, improving its utility for tracing aquatic organic matter.
• The study offers a foundation for more accurate carbon budget estimations and water quality management.