Dahl Rasmussen, A. AD. Roskilde University, adr@ruc.dk
Andersen, O. AD. Roskilde University, andersen@ruc.dk

 
MODELLING STUDIES OF FACTORS AFFECTING SEDIMENT-WATER CD TRANSFER IN ESTUARIES
 
The effect of salinity on transfer of Cd from sediment to water and vice versa was studied in the laboratory using 109-Cd gamma counting. Also, effects of salinity on the fractional amounts of various Cd species were assessed using the Minteq A2 Speciation Model. The rate constants for sediment uptake of Cd decreased with increasing salinity. Conversely, the rate of Cd release from sediment increased with increasing salinity. The modelling of speciation data indicated, that these transfer rates were determined by the fractional amount of non-chloro Cd species, i.e. mainly "free" hydrated Cd. As would be expected, the ratio between sediment surface and water volume affected the Cd transfer rates. Accordingly, water depth, water residence time, and degree of dilution with land run-off are expected to be important determinants of Cd kinetics in estuaries. Our data confirm the general notion, that the equilibrium of Cd partitioning in near-shore areas strongly favours sediment binding.
 
Day: Wednesday, Feb. 3
Time: Poster
Location: Sweeney Center
 
Code: SS28WE0703S