Heavy-metal accumulation in salt marshes from the Western and Eastern Scheldt
In: Science of the Total Environment. Elsevier: Amsterdam. ISSN 0048-9697; e-ISSN 1879-1026, more
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| Authors | | Top |
- Beeftink, W.G.
- Nieuwenhuize, J.
- Stoeppler, M.
- Mohl, C.
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| Abstract |
Heavy-metal contamination is assumed to have great consequences on the structure and functioning of ecosystems. Salt marshes may be especially threatened in some subsystems and/or processes by ecotoxic effects, because many of them are exposed to polluted estuarine and coastal waters.In three salt marshes in the Western Scheldt (WS), and one in the Eastern Scheldt (ES), soil and plant samples were taken from low, middle and high areas. For the trace-metal (Ni, Cu, Zn, As, Cd, Hg and Pb) analyses KFA used mainly electrothermal, cold-vapour and hydride AAS after various wet digestion procedures using closed as well as open systems. Solutions containing large amounts of Cd (plants) or Pb and Cd (soil) were analysed by flame AAS.Clay-metal correlations were highly significant for Ni, Cu and Pb, but only weakly for Cd. In the Bath marsh, nearest to the points of metal discharge, lower clay**—metal correlations were found than in the other marshes. Compared with other marsh soils those close to the port of Antwerp showed significantly higher levels of Cu, Cd and Hg. This also appeared to be the case for Zn and As. The highest marsh levels (with respect to tides) tended to have lower metal concentrations corresponding to their clay content**; exceptions may be related to an accumulation of metal-contaminated plant debris washed ashore.The contamination rate of the marsh sediments in theWestern Scheldt was estimated to be 2–3 for Cr and Cu, 4–5 for Zn, As and Pb, and 10 and 25 for Hg and Cd respectively. The Eastern Scheldt marshes showed a contamination rate of 2 or 3 for Zn, As, Pb and Cd.Except for Cd and Hg the metal concentrations in plant shoots appeared less indicative for the determination of the contamination rate of the marshes. Annual and short-lived perennial species tended to accumulate more Cd than long-lived perennials.Score spectra of metal concentrations in shoots suggest the presence of three main pathways of translocation in the selectivity and intensity of metal intake: (1) An Artemisia-Aster group accumulating Cd and Cu, (2) a Festuca-Plantago-Puccinellia-Triglochin group accumulating Hg, Ni and Pb, and (3) an Atriplex-Elytrigia-Halimione-Spartina group without distinct metal accumulation.A comparison of the Cd, Hg and Pb contents of Aster and Salicornia, both highly in demand as vegetables by the local people, with standard values accepted for green vegetables in the F.R.G. and the Netherlands was made. It is recommended that persons, who eat these wild plants as a regular food, be dissuaded from collecting them from the brackish marshes of the Western Scheldt. |
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