THE ATMOSPHERIC INPUT OF NITROGEN SPECIES TO THE NORTH-SEA

An assessment of atmospheric inputs of nitrogen to the southern North Sea (south of 56-degrees-N) has been made following a series of research cruises between August 1988 and October 1989. During which wet and dry sampling for aerosol and gaseous species was undertaken. Wet and dry deposition appear to contribute approximately equally to total deposition, yielding fluxes of 126 x 10(3) t N a-1 and 102 x 10(3) t N a-1, respectively. A tentative assessment for the northern North Sea has been made based on extrapolation from data generated here and from coastal sites. When combined with fluxes calculated for the southern area, the total atmospheric deposition of nitrogen to the whole North Sea is estimated to be 412 x 10(3) t a-1. In terms of gross nitrogen inputs to the North Sea, the contribution from the atmosphere is relatively minor, the budget being dominated by the influence of the North Atlantic inflow. However, it does represent at least 26% of the terrestrial input. Furthermore, the effects of both seasonality in inputs and remoteness from estuarine influence suggest that during the growing season, when primary production in the North Sea is often nutrient limited, the atmosphere may provide the dominant source of nitrogen in stratified areas away from the coast, and at a time when the tong-term trend in European emissions of NH3 and NO(x) to the atmosphere is upward.