The general aim of this research is to achieve a better understanding of the pathways controlling the air-sea exchange fluxes of Hg (deposition and emission fluxes). In the North Sea experiment (Sept. 1992) this was aimed by measuring Hg concentrations (gaseous, particulate and in rainwater) along an air mass on two research vessels aligned downwind. Results are interpreted in function of meteorological data as well as additional data on rainfall scavenging of major ions and pollutants. Intercalibration experiment was performed in Mace Head (Ireland) on April 1991. Sampling was carried out in the North Sea with the RV Belgica and FS Alkor during 04-27 Sept. 1991 and a North Sea Platform experiment was conducted during 08-22 Sept. 1992.