On the behaviour of copper,zinc, iron and manganese, and evidence for mobilization processes in the Dutch Wadden Sea
Duinker, J.C.; van Eck, G.Th.M.; Nolting, R.F. (1974). On the behaviour of copper,zinc, iron and manganese, and evidence for mobilization processes in the Dutch Wadden Sea. Neth. J. Sea Res. 8(2-3): 214-239 In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579; e-ISSN 1873-1406, more |  |
| Authors | | Top | - Duinker, J.C.
- van Eck, G.Th.M., more
- Nolting, R.F.
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| Abstract | Water, suspended sediment and bottom sediment samples in the western part of the Dutch Wadden Sea have been analyzed for their metal content (Cu, Zn, Mn, Fe). For sediment samples the total amount, the exchangeable and leachable fractions of these metals were determined, in order to distinguish the fraction of trace elements incorporated into the sediments by river water and sea water from the fraction that occurs in preexisting minerals. It was found that the metals investigated are mobilized in bottom sediment, increasing the levels in the interstitial water to high values. Evidence is given for the existence of a very fine fraction, probably consisting of colloidal iron and manganese oxides including trace elements, that do not settle under the prevailing conditions in the Wadden Sea. Data of tidal stations indicate that exchange of metals between interstitial water and overlying water takes place under particular hydrographic and meteorological conditions giving rise to short-term increases in the waterphase levels. The levels of metals in total suspended sediment are lowered by "dilution" with heavier particles with lower metal content eroded from the bottom. The levels in suspended matter cannot be reproduced by the mere process of bottom erosion even after correction for the particle size effect (fraction < 16um). Tidal action and reducing conditions are partly responsible for mobilization processes to occur, at the same time they reduce the net accumulation of metals in the Wadden Sea. The very fine fraction with a relatively high metal content will settle elsewhere, perhaps in deep ocean. The ecological significance of metals in the Wadden Sea, for example the uptake by bottom organisms, may be underestimated if only metal concentrations in bottom matter are considered in stead of in suspended matter as well. Removing the tidal action from an area where these conditions prevail may cause high metal concentrations in interstitial water with great ecological significance. |
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