Redox processes in recent sediments of the river Meuse, The Netherlands

Pore-water concentrations of inorganic solutes were measured at four locati ons in a recent sedimentation area of the river Meuse in The Netherlands. T he pore-water concentration profiles were interpreted using the steady stat e one-dimensional reaction/transport model STEADYSED1. This model explicitl y accounts for the organic matter degradation pathways and secondary redox reactions. Results show that the model reproduces the measured pore-water p rofiles of redox species reasonably well, although significant divergence i s observed for pH. The latter is due to the absence of pH buffering by CaCO 3 in the model. At all locations, methanogenesis is the major pathway of or ganic matter degradation below 3 cm from the sediment-water interface. Howe ver, organic matter degradation rates by methanogenesis may be overestimate d, because methane ebullition is not included. Differences in profiles of r edox-sensitive ions among the four locations are explained by differences i n depositional conditions, in particular the sediment accumulation rate and supply of organic matter.