THE ATMOSPHERIC DISTRIBUTIONS OF TRACE-METALS, TRACE ORGANICS AND NITROGEN SPECIES OVER THE NORTH-SEA

A 15 month survey was carried out into the distributions of trace meta ls, trace organics and nitrogen species in particulate and rainwater s amples collected from the atmosphere over the southern North Sea. This is the first time a comprehensive and reliable data-set of this kind has been obtained for a coastal region from collections made at sea. T race metals. There is a south-north decrease in the emission of trace metals to the atmosphere from the land masses surrounding the North Se a. 'End-member' aerosol trace metal concentrations have been identifie d for the three major source regions; i.e. continental Europe, U.K. an d the open-sea, and indicate that, in general, aerosols from air masse s which have crossed continental Europe are richer in some trace metal s (e.g. Zn and Pb) than those from air masses which have crossed the U .K. There are short-term variations in the concentrations of trace met als in aerosols over the North Sea; however, on an integrated long-ter m basis the concentrations reflect land-based source emission strength s, and increase towards the south of the region. There is also pronoun ced short term variability in the concentrations of trace metals in ra inwaters collected over the North Sea, but separate contributions from marine, crustal and anthropogenic sources can be identified. Atmosphe ric fluxes contribute substantially to the total inputs of trace metal s to the North Sea, with both 'wet' and 'dry' deposition processes bei ng important. Particulate trace organics. The distributions of three m ain hydrocarbon classes were studied; i.e. saturated hydrocarbons (n-a lkanes), PAH (polynuclear aromatic hydrocarbons) and UCM (uncharacteri zed complex material). Carbon preference indices of n-alkanes suggest that terrestrial sources dominate, with marine sources being insignifi cant. In terms of air mass origins, trace organic concentrations are r anked in the order: continental Europe > U.K. > open sea. ln terms of air mass origins, the concentrations of trace organics and some trace metals (e.g. Zn and Pb) are higher in aerosols having a continental Eu ropean than U.K. source. However, on the basis of predominant air mass trajectories over the survey period, the major source of both trace o rganics and trace metals to the North Sea atmosphere was air which had recently crossed over the U.K. Nitrogen species. Compared to the Nort h Atlantic sea water inflow, the atmosphere is a minor source of nitro gen species to the North Sea. However, atmospheric nitrogen inputs con stitute at least 25 % of the terrestrial inputs, and may provide the d ominant source of nitrogen in stratified areas of the North Sea remote from riverine inputs. 'Wet' deposition processes dominate the total n itrogen flux to the sea surface, but 'dry' deposition of gaseous and p articulate species contributes significantly.