Atmospheric nitrogen input into the North Sea: inorganic and organic nutrient fluxes. Final report EV/39

The North Sea is threatened by eutrophication. Excess supply of nutrients, especially nitrogen compounds, causes proliferation of algae, leading to pernicious oxygen depletion. The nitrogen supply is not only due to rivers, but to the atmosphere as well. Especially in summer, when nutrients are scarce and the river supply is reduced, the atmospheric contribution can become predominant. The relevant atmospheric nitrogen is emitted as nitrogen oxides (by traffic and industry) and as ammonia (by agriculture). Organic nitrogen compounds might be important but their deposition fluxes are unknown.Measurements of the concentrations of the various inorganic and organic nitrogen components and of their deposition, with rain and in the dry phase, will allow evaluating the contribution of the atmosphere to eutrophication processes, using adequate mathematical models.