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Title: Zinc in estuaries (Note 390)
Author: M. Gardner
Author: S. Comber
Author: J. Ravenscroft
Document Type: Monograph
Concentrations of dissolved zinc close to or above the Environmental Quality Standard have been observed in marinas and estuarine waters. It has been proposed that dissolution of sacrificial zinc anodes used in marinas and on leisure boats might cause increased levels of zinc at some locations. This project has the aim of investigating the sources of zinc contamination in estuaries and of providing an indication of how elevated levels might arise and how they can be controlled. In particular, the project was intended to assess the contribution of zinc anodes to concentrations of the metal in marinas and coastal waters. This work shows that the increase in zinc levels in estuaries due to anode use is likely to be small in relation to the current Environmental Quality Standard. Nevertheless sacrificial anodes can be expected to lead to measurable increases in concentrations of dissolved zinc in marinas and, to a lesser extent, in nearby estuary areas. Zinc from anodes is released initially into the dissolved phase. The rate of adsorption to finely divided particulate matter is sufficiently fast to ensure that a large proportion of the metal is transferred relatively quickly from solution to suspended sediments. The division between the contaminated sediment which remains in the marina and that which leaves the marina on the outgoing tide will depend on local conditions. Whilst it is necessary to continue to monitor concentrations of dissolved zinc in estuaries, more attention might need to be paid to concentrations of the metal in sediments, particularly in the vicinity of marinas. Recommendations are made concerning steps which might be taken to improve the quality of sample collection and filtration for trace metal monitoring. These include provision of guidance on control of contamination, adoption of a common approach to sample filtration and more widespread use of field blanks.
Publisher: National Rivers Authority
Publication Date: 1995
Publication Place: Bristol
Subject Keywords: ZincEstuariesHarboursQuality controlsEnvironmental monitoringSampling
Geographic Keywords: Poole HarbourOrwell EstuaryDeben Estuary
Extent: 36; + appendices
Total file downloads: 323

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