Ozone Risk Assessment - O3FLUX

The DO3SE ozone flux model (Emberson et al. 2005)

Rationale

Within the frame work of the UNECE Convention on Long-Range Transboundary Air Pollution, the WSL investigates the assessment of ozone risk for forest ecoystems on the basis of ozone fluxes on a European-wide level.

The scientific community agrees that from a plant physiological point of view a flux-based approach is superior over the currently applied concentration based (AOT) approach. However, for forest trees, the current state of knowledge allows a simplified and so far not-validated flux approach only. In order to improve the accuracy of the flux approach, it was suggested

- to establish a European-wide network of sites where dose-response relationships can be studied to validate the suggested EMEP-photooxidant flux model,

- to establish experimental free air fumigation systems to allow mechanistic studies excluding influencing factors as they may occur in chamber studies,

- to consider further plant physiological plant response parameters - in addition to the so far applied growth parameter – for the investigation of dose-response relationships.

Objectives

Based on the current discussions, resulting conclusions and the identified gaps of knowledge on the development and application of a flux-based concept to protect European forest ecosystems from tropospheric ozone, we aim to contribute towards the development of a scientifically robust flux-based model parameterization to quantify the flux-response relationships under real field conditions across Switzerland. In particular, we aim

1. To parameterize the DO3SE model for selected Swiss Level II plots.
2. To apply the DO3SE model and quantify a potential critical flux on the basis of flux-response relationships for parameters such as visible ozone injury on bio-indicators (PO3PLAR) on selected Level II plots.
3. To validate the DO3SE model based on sap-flow and gas-exchange data on selected Level II plots.
4. To produce a species specific ozone risk (relative) map for Switzerland, based on Beech and Norway Spruce.
5. To compare our results with the EMEP stomatal uptake model and AOT40 approach.  
6. To further develop the UNECE/ICP Forests monitoring program in combination with the PO3PLAR bio-indicator approach to assess AOT40.
7. To further strengthen the collaboration and foster the exchange of knowledge with the international ozone flux community.

Expected results

Our findings and results are expected to be used for the parameterization and validation of the EMEP-photooxidant flux model which is currently being refined within the framework of the UNECE Convention on Long-Range Transboundary Air Pollution, leading to a revised version of the Gothenborg Protocol to abate acidification, eutrophication and ground-level ozone.

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External collaborators

- Prof. R. Matyssek, TU Munich, Germany

- Dr. G. Wieser, Research and Training Centre for Forests, Austria

- Dr. S. Braun, IAP, Basel, Switzerland

- Dr. R. Häsler, Emeritus, WSL Birmensdorf, Switzerland

- Dr. L. Emberson, University of York, UK

- Dr. P. Büker, University of York, UK

- Dr. Davis Simpson, EMEP and The Norwegian Institue for Air Research, Kjeller, Norway

The funding has been provided by the Federal Office for the Environment FOEN, Switzerland.