Fluxes of oxidised and reduced nitrogen above a mixed coniferous forest exposed to various nitrogen emission sources

Concentrations of nitrogen gases (NH 3, NO 2, NO, HONO and HNO 3) and particles (pNH 4 and pNO 3) were measured over a mixed coniferous forest impacted by high nitrogen loads. Nitrogen dioxide (NO 2) represented the main nitrogen form, followed by nitric oxide (NO) and ammonia (NH 3). A combination of gradient method (NH 3 and NO x ) and resistance modelling techniques (HNO 3, HONO, pNH 4 and pNO 3) was used to calculate dry deposition of nitrogen compounds. Net flux of NH 3 amounted to −64 ng N m −2 s −1 over the measuring period. Net fluxes of NO x were upward (8.5 ng N m −2 s −1) with highest emission in the morning. Fluxes of other gases or aerosols substantially contributed to dry deposition. Total nitrogen deposition was estimated at −48 kg N ha −1 yr −1 and consisted for almost 80% of NH x . Comparison of throughfall nitrogen with total deposition suggested substantial uptake of reduced N (±15 kg N ha −1 yr −1) within the canopy. Reduced nitrogen was found to be the main contributor to total deposition which was predominantly governed by dry deposition.