THE BIOGEOCHEMICAL BEHAVIOR OF CD, CU, PB AND ZN IN THE SCHELDT ESTUARY - RESULTS OF THE 1995 SURVEYS

Cu, Cd, Zn and Pb concentrations in both dissolved and particulate pha se were assessed during 1995. Data Quality Assurance was an integral p art of this study and involved all major steps of the analysis procedu re such as sampling, sample handling, preconcentration and determinati on. Desorption and redox processes clearly control the dissolved Cu an d Cd profiles. Mobilisation of dissolved Zn is small and essentially r estricted to the low salinity area and the late spring survey. Dissolv ed Pb shows the dearest dilution pattern. The parameters representativ e of these processes (dissolved oxygen and salinity) also correlate ve ry well with the particulate metal profiles.In addition, the plankton activity (expressed by the chlorophyll-a levels) may influence the dis solved and particulate metal profiles. In combination with desorption and redox processes, seasonal variations were induced.