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Updated: May 17, 2026

Single-throughput Complementary High-resolution Analytical Techniques for Characterizing Complex Natural Organic Matter Mixtures
Published on: January 7, 2019
Origin of heat-induced structural changes in dissolved organic matter
Martin Drastík1, František Novák, Jiří Kučerík
1Charles University in Prague, Faculty of Pharmacy in Hradec Králové, Czech Republic.
Humic and fulvic acids exhibit distinct temperature-induced structural changes affecting their hydration and reactivity. These findings are crucial for understanding the environmental transport and sequestration of hydrophobic compounds.
Area of Science:
- Environmental Chemistry
- Supramolecular Chemistry
- Physical Chemistry
Background:
- Humic substances (HS) are vital in environmental processes, including the sequestration and transport of hydrophobic compounds.
- Their supramolecular nature provides flexibility and variable reactivity under different conditions.
Purpose of the Study:
- To investigate heat-induced transitions and hydration shell characteristics of humic and fulvic acids.
- To understand how temperature and concentration affect the structure and reactivity of these substances.
Main Methods:
- Ultrasonic velocimetry was employed to study sodium salts of humic and fulvic acids.
- Measurements were conducted across a temperature range of 5 to 90 °C.
Main Results:
- Distinct differences in the stability and hydration of humic substances were observed above and below 1 g L(-1) concentration.
- Adiabatic compressibility showed concentration-dependent behavior, with relaxation and intrinsic parts being significant at higher concentrations.
- Temperature-induced transitions around 17 °C (H-interactions) and 42 °C (aromaticity) were identified, along with hysteresis in structural relaxation.
Conclusions:
- Dissolved humic substances show temperature and thermal history-dependent conformation and reactivity.
- These structural changes likely influence the environmental transport and sequestration of hydrophobic pollutants.
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