Dry deposition of reactive nitrogen to European ecosystems: a comparison of inferential models across the NitroEurope network 1INRA, Agrocampus Ouest, UMR 1069 SAS, Rennes, France
23 Mar 2011
2Center for Ecology and Hydrology (CEH) Edinburgh, Penicuik, UK
3ECN, Netherlands Energy Research Foundation, Petten, The Netherlands
4EMEP MSC-W, Norwegian Meteorological Institute, Norway
5Department Earth & Space Sciences, Chalmers University of Technology, Gothenburg, Sweden
6Environment Canada, Toronto, Canada
Received: 28 October 2010 – Published in Atmos. Chem. Phys. Discuss.: 01 December 2010 Abstract. Inferential models have long been used to determine pollutant dry deposition
to ecosystems from measurements of air concentrations and as part of
national and regional atmospheric chemistry and transport models, and yet
models still suffer very large uncertainties. An inferential network of 55
sites throughout Europe for atmospheric reactive nitrogen (Nr) was
established in 2007, providing ambient concentrations of gaseous NH3,
NO2, HNO3 and HONO and aerosol NH4+ and NO3−
as part of the NitroEurope Integrated Project.
Revised: 14 March 2011 – Accepted: 14 March 2011 – Published: 23 March 2011
Network results providing modelled inorganic Nr dry deposition to the
55 monitoring sites are presented, using four existing dry deposition
routines, revealing inter-model differences and providing ensemble average
deposition estimates. Dry deposition is generally largest over forests in
regions with large ambient NH3 concentrations, exceeding 30–40 kg N ha−1 yr−1 over parts of the Netherlands and Belgium, while some
remote forests in Scandinavia receive less than 2 kg N ha−1 yr−1.
Turbulent Nr deposition to short vegetation ecosystems is generally
smaller than to forests due to reduced turbulent exchange, but also because
NH3 inputs to fertilised, agricultural systems are limited by the
presence of a substantial NH3 source in the vegetation, leading to
periods of emission as well as deposition.
Differences between models reach a factor 2–3 and are often greater than
differences between monitoring sites. For soluble Nr gases such as
NH3 and HNO3, the non-stomatal pathways are responsible for most
of the annual uptake over many surfaces, especially the non-agricultural
land uses, but parameterisations of the sink strength vary considerably
among models. For aerosol NH4+ and NO3− discrepancies
between theoretical models and field flux measurements lead to much
uncertainty in dry deposition rates for fine particles (0.1–0.5 μm). The
validation of inferential models at the ecosystem scale is best achieved by
comparison with direct long-term micrometeorological Nr flux
measurements, but too few such datasets are available, especially for
HNO3 and aerosol NH4+ and NO3−.
Citation: Flechard, C. R., Nemitz, E., Smith, R. I., Fowler, D., Vermeulen, A. T., Bleeker, A., Erisman, J. W., Simpson, D., Zhang, L., Tang, Y. S., and Sutton, M. A.: Dry deposition of reactive nitrogen to European ecosystems: a comparison of inferential models across the NitroEurope network, Atmos. Chem. Phys., 11, 2703-2728, doi:10.5194/acp-11-2703-2011, 2011.