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Redox Conditions Affect Dissolved Organic Carbon Quality in Stratified Freshwaters
journal contribution
posted on 2017-11-07, 00:00 authored by Tallent Dadi, Mourad Harir, Norbert Hertkorn, Matthias Koschorreck, Philippe Schmitt-Kopplin, Peter HerzsprungThe quality of dissolved organic
carbon (DOC) affects both carbon
cycling in surface waters and drinking water production. Not much
is known about the influence of environmental conditions on DOC quality.
We studied the effect of redox conditions on the chemical composition
of DOC in a drinking water reservoir by Fourier transform ion cyclotron
resonance mass spectrometry in combination with sediment core incubation
experiments under manipulated redox conditions. We observed clear
differences in DOC quality among oxic epilimnion, anoxic hypolimnion,
and sediment porewater. Sediment porewater showed relatively high
intensities of polyphenol-like components with H/C ratios of <1
and O/C ratios of >0.6. Consistent with this, anoxic incubation
of
a sediment core resulted in an accumulation of these components in
the overlying water. The observed pattern of DOC quality change can
be explained by redox-dependent adsorption/desorption of DOC on iron
minerals. Under oxic conditions, the polyphenol-like components bind
on freshly formed iron hydroxides, a process that affects both DOC
stability in surface waters and treatability during drinking water
production.