Dissolved Humic Substances

DOM scheme   figure: F.-D. Kopinke / UFZ
Scheme of time-resolved
 in-tube solid-phase
microectraction (TR-IT-SPME)

Humic substances are complex organic macromolecules which are formed during decay and transformation of plant and microbial remains. They form a major component of natural organic matter - as solids in soils and sediments or in dissolved form in aquatic systems.

Interactions of organic compounds with dissolved humic substances (DHS) are a major research field in the department. Especially in case of hydrophobic (low water-soluble) organic compounds sorption to DHS can strongly affect their fate in the environment.

For studying sorption equilibria we use solid-phase microextraction (SPME) as well as the fluorescence quenching technique (FQT). In order to investigate the kinetics of sorption/ desorption processes with a high-time resolution we developed a new experimental technique, the so called time-resolved in-tube solid-phase microextraction (TR-IT-SPME). This method allows to trace desorption processes which run in a time scale of a few seconds.

As amphiphilic, surface-active molecules, DHS can affect mass transfer processes at phase boundaries, such as water/air exchange of organic compounds. In this respect, we study direct effects of DHS on the hydrodynamics at the water surface and indirect effects, which occur when hydrophobic compounds are transported in the form of a complex with DHS (‘shuttle effect’).

Chemical transformation of organic contaminants (e.g. by hydrolysis, oxidation or reduction) can as well be affected by sorption to DHS. A fundamental understanding of these effects as a basis for development of improved strategies for prevention or remediation of environmental contaminations is the goal of our research.