Dissolved concentrations were determined for Fe, Mn, Al, Cu, Zn, La, U, Th,
Cd and As in a wetland and its recipient stream to reveal the effect of se
asonal changes in environmental conditions on the cycling and transfer of t
race elements at the transition between terrestrial and aquatic ecosystems.
These preliminary results from the wetland show marked seasonal changes in
dissolved concentration for all elements except Zn and Cu. Concentrations
are found to be low until about mid-February and then increase abruptly. Th
e onset of trace element release appears to coincide with a marked decline
in redox potential and increase of organic carbon content. Because this dec
line is itself correlated with a pronounced increase in temperature and dis
solved Fe, Mn and organic carbon content, we suggest that the microorganism
s which use soil iron and manganese oxy-hydroxides as electron accepters ca
talyzed the change in redox conditions and induced an increase of DOC. Temp
oral changes were also observed in the recipient stream which showed marked
positive concentration peaks during stormflow events (except Zn). The seas
onal processes occurring in the wetland appear to play a major role in dete
rmining the amount of trace elements which are transferred from the wetland
to the river. (C) 2001 Elsevier Science Ltd. All rights reserved.