Scientific Concept

The critical loads and levels concept is an effects-based approach, in accordance in particular with article 7(d) of the Convention, assisting to develop emission control strategies in the UNECE region.  It is based upon the definitions of critical loads and levels, currently for acidification, eutrophication and heavy metals as well as for other gases besides ozone. Critical load and level values depend on the target receptor, such as forest ecosystems, surface waters and others.

Measured and modelled pollutant concentrations and deposition rates, as well as pollutant scenarios are compared to critical loads and levels. The ICP Modelling & Mapping develops maps of critical loads and levels for various ecosystems and sensitive receptors for comparison with pollutant concentration and deposition data.

This results in maps showing where and how much critical loads and levels are exceeded, and therefore indicating the need of further emission abatement. Critical loads and levels and their exceedances are one main input for integrated assessment models, which are used to identify and evaluate European abatement strategies, taking technical and economic feasibility of proposed measures into account. Thus, the critical loads and levels concept is an important tool for policy planning, assisting the Convention's goal to improve the quality of life for the European people.

Figure: The comparison of critical loads and levels with European concentration and deposition data result in exceedance maps that show the magnitude and spatial distribution of risk. Integrated assessment models are used to develop and evaluate pollutant abatement strategies

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