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The influence of plants on concentration and fractionation
of Zn, Pb, and Cu in salt marsh sediments (Tagus Estuary,
Portugal)
Isabel Caçador, Carlos Vale* & Fernando
Catarino
Institute of Oceanography, Faculty of Sciences, University
of Lisbon,
Rua Ernesto Vasconcelos, Campo Grande, 1700 Lisboa, Portugal;
* Portuguese institute for Maritime Research, Av. Brasilia,
1400 Lisboa, Portugal
Received 21 November 1995; accepted in revised
form 30 April 1 1996
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Abstract
Sediment cores were collected from two sites of the
Tagus estuary salt marshes which differed in degree of metal contamination.
At each site, six 60-cm-long cores were taken, tree from a non-vegetated
intertidal zone, and one from each of areas colonized by salt marsh
plants, Spartina maritima, Halimione portulacoides
and Arthrocnemum fruticosum, respectively. Total concentrations
and concentrations in sequential extractions of Zn, Pb, and Cu were
determined in several sediment layers. Sediment slices containing
most of the roots (5-15-cm depth) were enriched in metals in comparison
with other depths in the core and with non-vegetated cores. Additionally,
metals in sediment slices with roots were preferentially linked
to the residual fraction. These results are evidence that aquatic
plant roots can have a strong influence on metal concentration and
speciation in sediments. Since metals become immobilized in vegetated
sediments, the preservation of salt marshes or the creation of artificial
wetlands could be considered as an efficient natural means for maintaining
ecosystem health or restoring ecosystem quality.
Keywords: metals, availability, ecosystem, restoration
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