Processes affecting deposition of oxidised nitrogen and associated species in the coastal areas of Norway

Measurement data on air, precipitation and canopy throughfall chemistry from a network of sites have been combined to study scavenging and deposition processes, with particular emphasis on the oxidised nitrogen species. High deposition rates of oxidised nitrogen occur in coastal areas of SW Norway. These are partly caused by high precipitation rates, partly also because a large fraction of the oxidised nitrogen is present as nitrate in large particles, which are rapidly removed by both wet and dry deposition processes. High wind speeds near the coast result in high concentrations of sea-salt particles in the air and high deposition rates of both nitrate and sea-salt particles, particularly in coniferous forest stands. HNO3 contributes on average only about 10–20% to the sum of aerosol nitrate and HNO3 (sNO3). Still, the combined dry deposition velocity of sNO3 to these forest stands may be between 4 and 6 cm s−1 on average.