10.1021/acs.est.7b04194.s001 Tallent Dadi Tallent Dadi Mourad Harir Mourad Harir Norbert Hertkorn Norbert Hertkorn Matthias Koschorreck Matthias Koschorreck Philippe Schmitt-Kopplin Philippe Schmitt-Kopplin Peter Herzsprung Peter Herzsprung Redox Conditions Affect Dissolved Organic Carbon Quality in Stratified Freshwaters American Chemical Society 2017 DOC quality ion cyclotron resonance mass spectrometry redox conditions surface waters DOC quality change sediment core incubation experiments Dissolved Organic Carbon Quality polyphenol-like components bind drinking water production drinking water reservoir 2017-11-07 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Redox_Conditions_Affect_Dissolved_Organic_Carbon_Quality_in_Stratified_Freshwaters/5612812 The 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.