ccc & msc-w - EMEP

The first figure, for acidifying sulphur, shows the total sulphur mass deposited over the country
each year and shows the effect of this deposition as the total mass contributing to exceedances
of the 5th percentile conditional critical load. In general, trends in the exceedances follow the
trends in sulphur and nitrogen deposition.
The acidifying sulphur figure includes also a curve depicting the time evolution of deposition
of transboundary origin to the specific country. Differences between total deposition and
transboundary deposition give a good measure of the importance of indigenous deposition in
the country. In many cases, specially over central European countries, it can be seen how the
relative contribution of transboundary deposition has increased after the emissions from the
countries themselves have decreased. Direct comparison between the emissions and
depositions values allows a first analysis of the country balance of imported vs exported
deposition.
The second figure serves for the analysis of acidifying and eutrophying nitrogen. Excess
nitrogen deposition contributes to acidification but can also lead to the eutrophication of soils
an surface waters. Thus, to analyse the effects caused by excess nitrogen deposition both a
conditional critical for acidity and a critical load of nutrient nitrogen need to be considered.
The conditional critical load for acidifying nitrogen depends both on sulphur and nitrogen
deposition, and thus the acidifying nitrogen exceedance trend depends both on sulphur and
nitrogen deposition trends. The critical load for eutrophying nitrogen does not depend on
sulphur deposition and therefore the eutrophying exceedances follow more generally the
nitrogen depositions.
The third figure gives the time evolution of the area of ecosystems with exceedance of the 5th
percentile critical loads. The curves represent the time evolution of the ecosystem area exposed
to possible exceedances, as percentage of the total country area. Here, the geographical
distribution of the considered ecosystems plays an important role. Inter-annual meteorological
variations can affect the pollution transport patterns, resulting in large changes in the
percentage ecosystem area with exceedances of the 5th percentile. Larger deposition amounts
over the country, do not necessarily imply larger ecosystem area with registered exceedances
because both the deposition levels and the geographical distribution of sensitive ecosystems
determine the changes in the ecosystem area.
Figures 1.2 a), b) and c) summarise the analysis for all countries in Europe that are Parties to
the Convention except Georgia, Iceland, Liechtenstein, Malta and Turkey. Georgia was not
included in this year’s calculations because the information that the country had ratified the
CLRTAP on February 2nd 1999 did not reach MSC-W in time for the model calculations. The
emissions from Malta and Liechtenstein are so low that their depositions are below the
precision limits of the model calculation of transboundary fluxes. Finally, Iceland and Turkey
are not included either because there is no critical load data available for these countries.
The transboundary deposition in these figures is the sum of total deposition in the individual
countries that originates outside of their boundaries. For all these EMEP countries,
transboundary depositions represent between 55-60% of the total deposition for sulphur, and
between 40-50% of the total deposition for nitrogen. Although emissions have decreased, the
distribution of sources in the different countries has not given the same type of reduction of in
the depositions.
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