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Diagenesis in subrecent marine sediments in the Eastern Scheldt, southwest Netherlands
Oenema, O. (1988). Diagenesis in subrecent marine sediments in the Eastern Scheldt, southwest Netherlands. Neth. J. Sea Res. 22(3): 253-265
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579; e-ISSN 1873-1406, meer
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| Abstract |
The diagenesis in fine-grained sediments from a 300 to 400-years-old Dunkirk deposit, exposed on the intertidal flat, was studied at a site in the Eastern Scheldt. A new in situ pore water sampling technique that allowed repeated sampling at exactly the same place was used to monitor the seasonal fluctuations in interstitial water composition. Concentrations of organic carbon (1.5 to 2%), nitrogen (C/N=19), phosphorus (500 µg·g-1) and manganese (250 µg·g -1) in the subrecent anoxic sediments were low, probably because they had already been depleted during earlier stages of diagenesis. Rates of organic carbon mineralization by sulphate reduction (0.1 Mole·m-2·y-1) and rates of nutrient regeneration were 1 to 2 orders of magnitude lower than in recent finegrained sediments elsewhere in the Eastern Scheldt. Pore water NH+4 and PO4 concentrations were controlled by mineralization, uptake by Zostera noltii and sediment-seawater exchange. During the summer the uptake exceeded the mineralization rate at 0 to 5 cm. Mineralization and diffusional processes dominated the changes in the NH+4 and PO4 profiles in the other seasons. Dissolved manganese and iron concentrations showed a typical subsurface maximum at 0 to 3 cm, and low ( < 5 µMole) concentrations below this depth. Dissolved iron concentrations were probably controlled by the solubility of iron sulphides, and manganese probably by the solubility of Mn, Ca-carbonate. |
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