Longitudinal change of riverine dissolved organic matter from source to sea and its photochemical and microbial transformation

Transformations of organic matter along large rivers from their headwaters to the estuaries are ecologically important, yet field studies combining full river transect sampling with degradation experiments remain scarce. We investigated the Elbe River from headwaters in the Czech Republic to the North Sea and combined longitudinal sampling with degradation experiments to (1) track longitudinal changes in dissolved organic matter (DOM) composition, (2) test photochemical and microbial degradation of terrestrial DOM from deadwood leachate in headwaters, (3) assess bacterial DOM consumption in downstream river stretches, and (4) evaluate photodegradation of organic micropollutants along the entire river. DOM composition shifted longitudinally from allochthonous-dominated, aromatic, oxygen-rich, high-molecular-weight compounds in headwaters to more saturated, nitrogen-enriched, low-molecular-weight components in the estuary. We found that bacterial degradation of terrestrial DOM was higher than photochemical loss in headwaters. Further downstream, bacteria then preferentially consumed younger, autochthonous, oxygen-rich DOM. Additional flume experiments showed substantial photodegradation of organic micropollutants over the river stretch. This unique dataset clarifies the dynamic transformations and pronounced variability of DOM across the land–ocean continuum.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Norbert Kamjunke, Helmholtz Centre for Environmantal Research (norbert.kamjunke@ufz.de)

Authors:

Peter Herzsprung, Helmholtz Centre for Environmental Research  (peter.herzsprung@ufz.de)

Wolf von Tümpling, Helmholtz Centre for Environmental Research  (wolf.vontuempling@ufz.de)

Jörg Tittel, Helmholtz Centre for Environmental Research  (joerg.tittel@ufz.de)

Martin Krauss, Helmholtz Centre for Environmental Research  (martin.krauss@ufz.de)

Oliver Lechtenfeld, Helmholtz Centre for Environmental Research  (oliver.lechtenfeld@ufz.de)