Trace metals in the eastern part of the North Sea: 1: Analyses and short-term distributions
Baeyens, W.F.J.; Gillain, G.; Decadt, G.; Elskens, I. (1987). Trace metals in the eastern part of the North Sea: 1: Analyses and short-term distributions. Oceanol. Acta 10(2): 169-179
Advanced analysis procedures for dissolved and particulate trace metals in sea water have been developed and tested in international intercalibration exercises. Since these tests gave evidence that reliable data could be produced with such methods, trace metal distributions in the coastal waters of the eastern North Sea were studied.The spatial distributions of most dissolved and particulate trace metals are, at least qualitatively, similar. Their concentrations decrease with distance from the coast and the mouth of the Scheldt estuary ( particulates much stronger than dissolved species). The salinity gradient is similar (but opposite) to the trace metals and turbidity gradients. The five trace metals studied can be subdivided into two groups on the basis of their KD ratios (particulate metal concentration to dissolved metal concentration). Hg and Pb are strongly associated with particulate matter (KD from 0.5 to1.5 offshore and from 7.9 to 40 in the coastal area), while Cd, Cu and Zn are predominantly in the dissolved phase (KD from 0.1 to 0.2 offshore -up to 0.5 for Zn- and from 1 to 1.7 in the coastal area).The distributions of the metal concentrations in suspended solids (mg.kg-1) are much more complex. Only the Pb distribution is similar to that of the turbidity, but also to those of the major inorganic elements in suspended sediments (Al, Fe, Mn) and the chlorophyll a content. However, the chlorophyll a content is, like the salinity, inversely correlated to the concentrations of the major inorganic elements. High X/Al (X=Cd, Cu, Hg, or Zn) ratios in suspended matter are observed at low suspended matter concentrations. Detrital organic matter is probably the main carrier of these trace metals. At high suspended matter concentrations, these ratios decrease and approach the reference soil value. Both the Scheldt estuary and resuspended bottom sediments may be the source of those high suspended matter concentrations. Fe/Al and Mn/Al ratios are high at high suspended matter concentrations and decrease at low turbidity. These particles enriched in Fe and Mn are supplied by the Scheldt estuary. Pb/Al and Fe/Al ratios appear to be correlated.
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