Aggregation and Sedimentation of Iron, Phosphorus and Organic Carbon in Experimental Mixtures of Freshwater and Estuarine Water

The importance of salinity and suspended minerogenic particles on the aggregation and sedimentation processes of iron, phosphorus and organic carbon was studied in experimental procedures with waters from the River Öre and from the Öre Estuary, northern Sweden. The aggregation of dissolved iron and phosphorus reached at least 40–90% and 30–60%, respectively, at salinities between 4 and 6. Only a few percent, less than 10%, of the dissolved organic carbon aggregated. Rapid and nearly complete sedimentation of iron and phosphorus aggregates was found at high salinities (4–5) and in the presence of clay particles. Mineral particles increase sedimentation by sorption of formed iron and phosphorus aggregates. Only a small amount of the organic carbon sedimented.