Colloidal and dissolved trace metals in northern Adriatic ultrafiltered waters

Water samples were collected in two areas of the northern Adriatic basin du ring a survey carried out in June 1996. The samples were processed, after p reliminary filtration (0.4 mu m) through an ultrafiltration system, to sepa rate colloidal from truly dissolved components. The role of colloidal mater ial in the transport and partitioning of trace metals (Cd, Co, Cu, Fe, Mn, Ni, Pb) in Northern Adriatic waters was examined in relation to salinity an d sampling location. Colloidal fractions contained on average 40, 51 and 53 % of the total dissolved concentrations of Ni, Cu and Fe and 34 and 37% of the total dissolved concentration of Cd and Co respectively; whereas Pb and Mn occurred preferentially (73%) in the truly dissolved fraction. All meta ls were more abundant in the low molecular weight colloidal fraction (betwe en 1 and 10 kD) than in the high molecular weight colloidal fraction (> 10 kD).