Factors affecting metal concentrations in the upper sediment layer of intertidal reedbeds along the river Scheldt

Factors that play a role in determining metal accumulation in sediments of 26 intertidal marshes which are mainly vegetated by reed plants (Phragmites australis) were assessed along the Scheldt estuary (Belgium and The Netherlands). In the upper 20 cm sediment layer, several physico-chemical propert...

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Bibliographic Details
Published in:Journal of environmental monitoring 2007-05, Vol.9 (5), p.449
Main Authors: Du Laing, Gijs, Vandecasteele, Bart, De Grauwe, Pieter, Moors, Wouter, Lesage, Els, Meers, Erik, Tack, Filip M G, Verloo, Marc G
Format: Article
Language:English
Subjects:
Aluminum Silicates - analysis
Belgium
Chlorides - analysis
Chromium - analysis
Copper - analysis
Geography
Geologic Sediments - analysis
Geologic Sediments - chemistry
Hydrogen-Ion Concentration
Lead - analysis
Metals - analysis
Netherlands
Nickel - analysis
Organic Chemicals - analysis
Poaceae - physiology
Risk Assessment
Rivers - chemistry
Soil Pollutants - analysis
Water Pollutants, Chemical - analysis
Zinc - analysis
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Summary:Factors that play a role in determining metal accumulation in sediments of 26 intertidal marshes which are mainly vegetated by reed plants (Phragmites australis) were assessed along the Scheldt estuary (Belgium and The Netherlands). In the upper 20 cm sediment layer, several physico-chemical properties (clay, silt and sand content, organic matter, carbonate and chloride content, pH and conductivity) and aqua regia extractable metals (Cd, Cr, Cu, Ni, Pb, Zn) were determined. The sediments were significantly contaminated with trace metals. The Cd concentrations often exceeded the Flemish soil remediation thresholds for nature areas, whereas Cr, Cu and Zn levels indicated moderate contamination. Pb concentrations occasionally were high, whereas Ni concentrations leaned towards background values. Organic matter was the single most important predictor variable for total metal contents in regression models, except for Cr. Additional significant predictor variables were clay or chloride content, depending on the metal. Observed metal concentrations at sites within a range of a few km from specific point-sources of metals (e.g. shipyards, industrial areas with metallurgic activities, affluents, major motorways) were somewhat higher than predicted by the models, whereas they were lower than predicted at sites which are regularly subjected to flooding by water of high salinity. The ratio between observed and predicted concentrations seems to be a valuable tool for the identification of areas which are specifically impacted by point sources.
ISSN:1464-0325
1464-0333
DOI:10.1039/b618772b