A number of man made pollutants, as nitrogen oxides and volatile organic
compounds (VOC), that can affect the photochemical activity, are emitted into
atmosphere. Nitrogen oxides are emitted mainly from combustion processes from
both mobile sources (e.g. road traffic) or stationary sources (e.g. power plants).
VOC are emitted from combustion and also by evaporation of fuels and solvents.
Furthermore natural emissions, in particular of hydrocarbon from trees, will
also contribute to the photochemical activity.
In the atmosphere these pollutants may react, producing other toxic pollutants (mainly
ozone). The production of ozone require sunlight. Therefore ozone above what is
considered harmful for the environment or for humans is mostly a problem in the
summer months. Both observations and calculations have shown that ozone has
increased on a local and regional scale in the European boundary layer.
Furthermore, ozone has increased by approximately a factor of two throughout the
lower atmosphere in the northern mid latitudes since early this century.
Exceedances of ozone considered harmful for humans and for the environment is
most frequent in central and southern parts of Europe. Close to the surface
nitrogen oxidants, hydrocarbons and ozone itself can build up in what is called
ozone episodes. In northern parts of Europe exceedances are not as frequent
mainly because the solar radiation is weaker further north. Both measurements
and models show that there has been a reduction in the magnitude of such ozone
events in Europe since the late 1980's as a result of emission reductions of
ozone precursors over the same period.
To avoid such pollution events emissions must be further reduced. However the
chemical mechanisms involved are complicated and there are still uncertainties
as to how reductions should be made cost effective (The maximum amount of
reductions for a given sum of money). In particular for nitrogen oxides
reductions are desirable also for other environmental reasons as acidification
and eutrophication.
The UNECE/EMEP emission database WebDab has been constructed in purpose to facilitate the access to the emission data reported to the Convention on Long-Range Transboundary Air Pollution (CLRTAP) on Main Pollutants among other compounds.
Contact: emep.emissions@umweltbundesamt.atMeasurement data is available for all EMEP stations.
Contact person: anne-gunn.hjellbrekke(@)nilu.noIn 1989, the MSC-W of EMEP began the work on the development of an ozone
model of adressing both the problem of short-term episodic ozone and long-term
(growing season) ozone. The model was called in the beginning the Lagrangian
Ozone model and is also known as the
Lagrangian Photooxidant model.
In 1997 results from the EMEP
Eulerian photooxidant model were presented for
the first time.
But this model has been revised and is documented in EMEP Status Report 1/03 Part I (available at:
common EMEP publications) and from 2003 the operational runs are done
with Unified EMEP model.
Modelled air concentration and deposition data are downloadable as ASCII files covering the whole EMEP grid. Source-receptor relationships by country of Sulphur and Nitrogen are downloadable as ASCII files, but also overview tables of Sulphur and Nitrogen are available.
Contact: emep.mscw@met.no