The aim of this work is to assess the importance of the colloidal fraction in the distribution of trace metals (Cd, Cu, Pb, Zn) in various continental aquatic systems: Lake Geneva (Switzerland-France), Vistula River (Poland) and Adour Estuary (France).

A significant methodological development is necessary. In particular, the preconcentration of trace metals onto chelating resin and the development of tangential flow ultrafiltration in ultra clean conditions to isolate the colloidal and truly dissolved fractions.

The main results are (1) quantitative and qualitative influence of the organic matter on the complexation of metals by experimental studies (laboratory and field) and by chemical modeling (MINTEQA2, MINEQL); (2) effects of the ionic strength on flocculation of the colloidal material in the estuary and the contaminated river; (3) influence of chemical speciation on bioavailability of trace metals in toxicity bioassays in laboratory.