DISSOLVED AND PARTICULATE TRACE METAL GEOCHEMISTRY IN THE SCHELDT ESTUARY, S.W. NETHERLANDS (WATER COLUMN AND SEDIMENTS)

摘要: The geochemistry of dissolved and particulate trace metals has been studied in the water column sediments Scheldt estuary between 1987 1990. A strong seasonal influence on behaviour Cd, Cu Zn is observed, related to redox conditions upper phytoplankton activity lower (which are both seasonally dependent variables). metal concentrations fresh end-member remarkably low during spring summer, due sulphide precipitation anoxic river. However, increase rapidly with increasing salinity, oxidation sulphides that present suspended matter, accompanied by (e.g. chloro-)complexation released metals. Readsorption Cd occurs bloom. During winter, when river not completely anoxic, much higher observed since precluded. Rapid removal high turbidity zone, adsorption onto matter freshly precipitated iron manganese oxyhydroxides. Upon further mixing, desorption apparent, a similar oxidation-complexation mechanism as summer. Pore infusion may also contribute enrichment mid-estuarine region. contents show continuous decrease salinity. This very large extent physical mixing contaminated fluvial particulates relatively unpolluted marine particulates. Desorption can be identified but minor importance compared conservative process. distribution pore waters region reflects impact early diagenetic processes. Trace peaks near sediment-water interface, at greater depth reduction zones. These attributed reduced compounds sulphides) (iron manganese) oxide carrier phases, respectively. At depth, sulphate zone. Analysis sediment dataset indicates severe pollution end fifties. major As, Cr, Hg, Pb, occurred seventies, eighties. Ni increased over time period considered. In spite this improvement, present-day status still reason for concern.