Country-dependent characterisation factors for acidification in Europe.

Goal, Scope and Background. Country-dependent characterisation factors for acidification have been derived for use in life cycle assessments to describe the effect on ecosystem protection of a change in national emissions. They have recently also been used in support of European air pollution abatement policies and related cost benefit analyses. We demonstrate that the characterisation factors as calculated to date are unstable due to being derived from the non-smooth and highly varying part of the underlying emission-impact functions. The purpose of this paper is to discuss the currently available characterisation factors and to propose a modification that makes use of the full range of the underlying functions. Method. The characterisation factors derived in this paper are based on updates of data used to support European air pollution agreements under the UNECE Convention on Long-range Transboundary Air Pollution (LRTAP) and the European Commission. The focus in this paper is on the analysis of characterisation factors for acidification. The analysis of characterisation factors for terrestrial eutrophication from nitrogen compounds is a simple extension of the methods described here. The analysis is conducted for 25 European nations, i.e. for 23 EU countries plus Norway and Switzerland; Cyprus and Malta are excluded due to lack of data on critical loads. Results and Conclusions. We show that a linear model which is calibrated to emission changes of -50% is generally more reliable than characterisation factors which are based on emission changes of plus or minus 10%. Application of these characterisation factors are justified for emission reductions up to 30% in total European emissions, compared to 2000. This is within the range of currently agreed upon emission reductions in 2010 relative to 2000. Therefore, characterisation factors can be used in LCA as well as for the support of the revision of existing European air pollution agreements

The history and current state of critical loads and dynamic modelling assessments

This book focuses on knowledge and methods for the assessment of indirect, soil mediated effects of the deposition of sulphur dioxide, oxidized nitrogen and reduced nitrogen on terrestrial and aquatic ecosystems. The emphasis is on the science behind no-effect deposition thresholds (critical loads) and methods to understand future consequences of atmospheric depositions that exceed these thresholds. First, background information is given on drivers and impacts of air pollution and the philosophy behind the critical load approach is pointed out. Then, the history and current state of critical load assessments for sulphur (S), nitrogen (N) and metals is presented. This is followed by recent developments and use of dynamic models, for the assessment of future impacts of excessive deposition and the chapter finalizes with a reading guideline to this book and the logic of its organization

Critical loads of sulfur and nitrogen

This paper describes the simple mass balance model (SMB) for calculating critical loads of sulphur and nitrogen on forest soils. It includes a complete overview of the mathematical descriptions for all the relevant input terms in the SMB model such asuptake, nitrogen transformation processes and alkalinity leaching. A distinction is made between methods using a constant and a deposition-dependent description of nitrogen sinks, such as denitrification. The simultaneous treatment of sulphur and nitrogen does not allow the calculation of a unique critical load. In this context, the concept of a protection isoline is introduced and mathematically described

Synthesis

This chapter first presents an overview of findings described in this book. This includes a summary of the combined use of empirical and model-based approaches, main results of these analyses, and their relevance in view of impacts on ecosystem health, human health and effects on ecosystem services. This is followed by a discussion of the uncertainties involved in critical load assessments and applications. Finally, it presents an outlook on the future of critical loads and dynamic model applications to support assessments of trade-offs between policies in the field of air pollution, biodiversity and climate change. The importance of analysing multiple rather than single effects in these fields, including their interactions, is emphasized as the way forward for the further development and application of critical thresholds