DETERMINATION OF SETTLING VELOCITY IN THE ELBE ESTUARY USING QUISSET TUBES

A Version of the Owen tube with reduced flow disturbance and wider ope rating concentration range -the UWB QUISSET- is described. Quasi in si tu settling velocity distributions of suspended particulate matter (SP M) were determined using these during an intercalibration exercise in the Elbe estuary in June 1993. Systematic Variation was observed, in r esponse to tidal resuspension, advection and redeposition. The observe d variation in median settling velocity was in good agreement with tha t obtained by other workers using different settling tubes. Systematic differences in absolute values of up to an order of magnitude between the various techniques may have been caused by differences in tube de sign, sample handling or raw data interpretation.