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

Concentrations of nitrogen gases (NH3, NO2, NO, HONO and HNO3) and particles (pNH(4) and pNO(3)) were measured over a mixed coniferous forest impacted by high nitrogen loads. Nitrogen dioxide (NO2) represented the main nitrogen form, followed by nitric oxide (NO) and ammonia (NH3). A combination of gradient method (NH3 and NOx) and resistance modelling techniques (HNO3, HONO, pNH4 and pNO(3)) was C used to calculate dry deposition of nitrogen compounds. Net flux of NH3 amounted to -64 ng N m(-2) s(-1) over the measuring period. Net fluxes of NO, 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 9 deposition. Total nitrogen deposition was estimated at -48 ka N ha(-1) yr(-1) and consisted for almost 80% of NHx Comparison of throughfall v nitrogen with total deposition suggested substantial uptake of reduced N (+/- 15 kg N ha(-1) yr(-1)) within the canopy. (c) 2007 Elsevier Ltd. All rights reserved.