The research within Theme 1 covers four environmental problems: Acidification and its recovery, Vegetation effects of nitrogen deposition, Ozone effects to crops and forests and Characterisation of long range transported particles.

Source-effect relationships and effect indicators used within the European co-operation on transboundary air pollution are presently in a process of strong development towards dynamic concepts aimed at estimating actual effects, the so called Level II, and recovery times of ecosystems.

The research is focussed on supporting the development of integrated assessment modelling with concepts, criteria, indicators and background material for target settings. The work will to a large extent be based on the work taken place in ASTA Phase I. The results obtained in Theme 1 will be presented and evaluated in appropriate international frameworks (workshops, conferences) and communicated to the Integrated Assessment Modelling (IAM) community.

Modelling of vegetation changes caused by nitrogen deposition will be performed. The vegetation model will also be linked to an integrated modelling tool for combined ecosystem effects. The assessment of vegetation changes will be based on experimental results obtained in ASTA Phase I and II.

ASTA will continue to contribute actively to the revision of the Mapping Manual of the CLRTAP in several ways, by participating in meetings and making suggestion of revisions in the manuals. ASTA intend to continue and to broaden the contribution to discussions of what criteria to use for acidification, eutrophication, ground-level ozone and particles-related problems. The goal is to ensure that mapping and monitoring activities along the new lines are undertaken in the whole of Europe.

In Theme 1 the research on the recovery of acidified ecosystems and effects of ozone started in Phase I will continue. The main focus of Phase II is to apply models on the European scale.

The work on atmospheric particles will contribute to the development of process models and to characterisation of physical and chemical properties of particles in relation to their sources and transport distances. ASTA Theme 1 will be the main co-ordinating activity for communicating and synthesising research in other national and international projects to the CLRTAP and CAFE.