THE SPATIAL-DISTRIBUTION AND PARTICLE-SIZE OF SOME INORGANIC NITROGEN, SULFUR AND CHLORINE SPECIES OVER THE NORTH-SEA

The use of filter packs and a cascade impactor during a series of research cruises in the southern area of the North Sea has yielded detailed spatial distribution patterns of aerosol concentrations, Cl-, NO3-, SO42- and NH4+, and gaseous concentrations, HCl, HNO3 and NH3. The overall distribution of the atmospheric concentrations closely parallels published modelled results for metallic species. The chemical transformation of these aerosols and gases are investigated together with their interactions with the seasalt aerosol. Aerosol chloride loss is greatest in the more polluted areas, whilst concentration products of NH3 with HNO3 and HCl appear insufficient to sustain the existence of NH4NO3 and NH4Cl. Nitrate is associated predominantly with larger particles and appears to be present substantially as a surface coating on marine aerosol. The total dry deposition input for nitrogen species is calculated for the southern sector with extrapolation to the whole of the North Sea, using particle size weighted deposition velocities of 0.63 and 0.21 cm s-1 for NO3- and NH4+, respectively, and literature-derived values for the gaseous constituents. Finally the use of air-mass back trajectories illustrates the role of source regions in influencing the chemical composition of the North Sea atmosphere.