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14 - Atmospheric transport and deposition of reactive nitrogen in Europe
- from Part III - Nitrogen flows and fate at multiple spatial scales
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- By David Simpson, Norwegian Meteorological Institute, Wenche Aas, NILU, Norwegian Institute for Air Research, Jerzy Bartnicki, Norwegian Meteorological Institute, Haldis Berge, Norwegian Meteorological Institute, Albert Bleeker, Energy Research Centre of the Netherlands, Kees Cuvelier, Frank Dentener, European Commission Joint Research Centre, Tony Dore, Centre for Ecology and Hydrology, Jan Willem Erisman, Energy Research Centre of the Netherlands, Hilde Fagerli, Norwegian Meteorological Institute, Chris Flechard, Soils, Agro-hydro systems and Spatialization, Ole Hertel, University of Aarhus, Hans van Jaarsveld, Netherlands Environmental Assessment Agency, Mike Jenkin, Atmospheric Chemistry Services, Martijn Schaap, TNO Built Environment and Geosciences, Valiyaveetil Shamsudheen Semeena, Norwegian Meteorological Institute, Philippe Thunis, European Commission Joint Research Centre, Robert Vautard, LSCE/IPSL laboratoire CEA/CNRS/VSQ, Massimo Vieno, University of Edinburgh
- Edited by Mark A. Sutton, NERC Centre for Ecology and Hydrology, UK, Clare M. Howard, NERC Centre for Ecology and Hydrology, UK, Jan Willem Erisman, Gilles Billen, Albert Bleeker, Peringe Grennfelt, Hans van Grinsven, Bruna Grizzetti
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- Book:
- The European Nitrogen Assessment
- Published online:
- 16 May 2011
- Print publication:
- 14 April 2011, pp 298-316
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- Chapter
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Summary
Executive summary
Nature of the problem
Observations of atmospheric reactive nitrogen (Nr) deposition are severely restricted in spatial extent and type. The chain of processes leading to atmospheric deposition emissions, atmospheric dispersion, chemical transformation and eventual loss from the atmosphere is extremely complex and therefore currently, observations can only address part of this chain.
Approaches
Modelling provides a way of estimating atmospheric transport and deposition of Nr at the European scale. A description of the different model types is provided.
Current deposition estimates from models are compared with observations from European air chemistry monitoring networks.
The main focus of the chapter is at the European scale; however, both local variability and and intercontinental Nr transfers are also addressed.
Key findings/state of knowledge
Atmospheric deposition is a major input of Nr for European terrestrial and freshwater ecosystems as well as coastal sea areas.
Models are key tools to integrate our understanding of atmospheric chemistry and transport, and are essential for estimating the spatial distribution of deposition, and to support the formulation of air pollution control strategies.
Our knowledge of the reliability of models for deposition estimates is, however, limited, since we have so few observational constraints on many key parameters.
Total Nr deposition estimates cannot be directly assessed because of a lack of measurements, especially of the Nr dry deposition component. Differences among European regional models can be significant, however, e.g. 30% in some areas, and substantially more than this for specific locations.
The atmospheric budget of oxidized nitrogen and its role in ozone formation and deposition
- DAVID FOWLER, CHRIS FLECHARD, UTE SKIBA, MHAIRI COYLE, J. NEIL CAPE
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- Journal:
- The New Phytologist / Volume 139 / Issue 1 / May 1998
- Published online by Cambridge University Press:
- 01 May 1998, pp. 11-23
- Print publication:
- May 1998
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- Article
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Emissions of reactive oxidized nitrogen (NO and NO2), collectively known as NOx, from human activities are c. 21 Tg N annually, or 70% of global total emissions. They occur predominantly in industrialized regions, largely from fossil fuel combustion, but also from increased use of N fertilizers. Soil emissions of NO not only make an important contribution to global totals, but also play a part in regulating the dry deposition of NO and NO2 (NOx) to plant canopies. Soil microbial production of NO leads to a soil ‘compensation point’ for NO deposition or emission, which depends on soil temperature, N and water status. In warm conditions, the net emission of NOx from plant canopies contributes to the photochemical formation of ozone. Moreover, the effect of NOx emissions from soil is to reduce net rates of NO2 deposition to terrestrial surfaces over large areas.
Increasing anthropogenic emissions of NOx have led to an approximate doubling in surface O3 concentrations since the last century. NOx acts as a catalyst for the production of O3 from volatile organic compounds (VOCs). Paradoxically, emission controls on motor vehicles might lead to increases in O3 concentrations in urban areas.
Removal of NO and NO2 by dry deposition is regulated to some extent by soil production of NO; the major sink for NO2 is stomatal uptake. Long-term flux measurements over moorland in Scotland show very small deposition rates for NO2 at night and before mid-day of 1–4 ng NO2-N m−2 s−1, and similar emission rates during afternoon. The bi-directional flux gives 24-h average deposition velocities of only 1–2 mm s−1, and implies a long life-time for NOx due to removal by dry deposition.
Rates of removal of O3 at the ground are also influenced by stomatal uptake, but significant non-stomatal uptake occurs at night and in winter. Measurements above moorland showed 40% of total annual flux was stomatal, with 60% non-stomatal, giving nocturnal and winter deposition velocities of 2–3 mm s−1 and daytime summer values of 10 mm s−1. The stomatal uptake is responsible for adverse effects on vegetation. The critical level for O3 exposure (AOT40) is used to derive a threshold O3 stomatal flux for wheat of 0·5 μg m−2 s−1. Use of modelled stomatal fluxes rather than exposure might give more reliable estimates of yield loss; preliminary calculations suggest that the relative grain yield reduction (%) can be estimated as 38 times the stomatal ozone flux (g m−2) above the threshold, summed over the growing season.