Bervoets, L.

Carpentier, R.

Maris, T.

Meire, P.

Teuchies, J.

Open Marine Archive

 - 17 -
SPATIAL AND SEASONAL VARIATIONS OF METAL CONCENTRATIONS 
IN SEDIMENTS FROM THE SCHELDT ESTUARY 
Carpentier Roos1, Johannes Teuchies1, Tom Maris1, Lieven Bervoets2 and Patrick Meire1 
1 Ecosystem Research Management Group, University of Antwerp 
Universiteitsplein 1, B-2610 Antwerpen (Wilrijk) 
E-mail: Johannes.Teuchies@ua.ac.be   
2 Ecophysiology, Biochemistry and Toxicology, University of Antwerp 
Groenenborgerlaan 171, B-2020 Antwerpen 
 
Estuaries concentrate pollutants carried along by rivers from the whole drainage basin into a 
relatively compact system that can be monitored more easily. They offer a last opportunity to 
control outputs to the marine environment where substances become diffuse and difficult to 
manage. Therefore, estuaries are crucial links in water quality management (Van Damme et al., 
2005). The Scheldt Estuary used to be heavily contaminated by metals. Current metal 
concentrations in the estuary have decreased, but historical contamination is still traceable in 
deposited sediments (Baeyens et al., 2005). Metals in aquatic environments can occur in a dissolved 
or particle-bound form. Both dissolved metals and metals bound to suspended solids in the water 
column can be transported towards the sea. 
 
The distribution of metals (As, Cd, Cr, Cu, Mn, Ni, Pb and Zn) in subtidal and intertidal sediments of 
the Scheldt Estuary is studied in field sampling campaigns. Subtidal samples are collected along the 
whole estuary, from Ghent to the mouth. Intertidal sediments are studied on a freshwater tidal flat 
and tidal marsh at about 103km distance from the river mouth. Both subtidal and intertidal samples 
show correlations between metal contents and sediment characteristics: metal concentrations 
correlate positively with the organic content of the sediment and negatively with its median grain 
size. Subtidal sediment metal concentrations in the estuary decrease towards the river mouth. This 
can be explained by (1) tidal mixing with less polluted suspended particles originating from the 
marine environment, (2) the degradation of organic particles and (3) the increase of dissolved 
oxygen and salinity, causing metal mobilization. 
 
Sediments on a freshwater tidal marsh contain higher metal concentrations than subtidal sediments 
at the same location. This difference is due to the smaller grain size and the larger organic content 
of the intertidal sediments. Seasonal variations in intertidal sediment metal concentrations result in 
lower concentrations during winter because of the larger median grain size which is caused by a 
higher river discharge. Deposition of suspended solids on tidal marshes causes retention of 
particle-bound metals in the estuary. 
 
The research described resulted in a Master’s thesis to obtain the degree of Master of Science of 
Biology.  
 
References 
Baeyens W., M. Leermaekers, M. De Gieter, H.L. Nguyen, K. Parmentier, S. Panutrakul and M. 
Elskens. 2005. Overview of trace metal contamination in the Scheldt Estuary and effect of 
regulatory measures. Hydrobiologia 540:141-154. 
Van Damme S., E. Struyf, T. Maris, T. Ysebaert, F. Dehairs., M. Tackx, C. Heip and P. Meire. 2005. 
Spatial and temporal patterns of water quality along the estuarine salinity gradient of the 
Scheldt Estuary (Belgium and the Netherlands): results of an integrated monitoring approach. 
Hydrobiologia 540:29-45. 


Spatial and seasonal variations of metal concentrations in sediments from the Scheldt estuary

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