Sulfur cycling and the sulfurization of humic and fulvic acids in the sediments of the rivers Rupel (Belgium) and Authie (northern France)

Sulfur cycling and the sulfurization of humic and fulvic acids were compared in recent sediments from two western European rivers (the heavily polluted River Rupel in Belgium and the pristine River Authie in northern France). The sulfurization of humic and fulvic substrates occurs in both sediments irrespective of organic loading, but the sulfur species added to the organic substrate differ. Some sulphurization of fulvic acid by oxidized S was observed in the strongly reducing sediment of the River Rupel. Humic acids were sulfurized in the sediments of both rivers in these segments with prevailing reducing conditions by reduced S