ETC HE Report 2022/23: Evaluation of European-wide map creation of flux-based ozone indicator POD for selected tree species.
O3 is considered to be the most damaging common air pollutant for vegetation. The current indicator used to protect vegetation against negative impacts of O3 is the AOT40. Nevertheless, it is widely acknowledged that the impacts of O3 are more closely related to the instantaneous O3 flux or O3 dose absorbed through the stomata than to O3 exposure in the ambient air. For this reason, maps of POD1 (i.e. Phytotoxic Ozone Dose) for tree species of beech and spruce have been prepared using the methodology described in the Manual for modelling and mapping critical loads and levels of the Air Convention (CLRTAP). Subsequently, it can be concluded that the inclusion of POD for selected trees in routine mapping along with the other maps already produced is feasible.
26 May 2023
Leona Vlasáková (CHMI), Jana Marková (CHMI), Frédéric Tognet (INERIS), Jan Horálek (CHMI), Augustin Colette (INERIS)
Ground-level ozone (O3) is a secondary photochemical pollutant formed in a complex photochemical chain reactions from its precursors. O3 is considered to be the most damaging common air pollutant for vegetation with adverse effects on crop yields and forest health. Currently, the indicator used in the European Directive 2008/50/EC to protect vegetation against negative impacts of O3 is the Accumulated Dose of O3 Over a Threshold of 40 ppb (AOT40). Nevertheless, it is widely acknowledged that the impacts of O3 are more closely related to the instantaneous O3 flux or O3 dose absorbed through the stomata than to O3 exposure in the ambient air. Therefore, an index based on stomatal O3 uptake such as Phytotoxic Ozone Dose (PODY), which considers the accumulated O3 flux entering into the leaves via stomata above a threshold Y, is more appropriate than a purely O3 concentration-based metric. The PODy metric takes into account the varying influences of climatic factors, O3 concentrations and plant phenology. The paper examines the potential inclusion of the Phytotoxic Ozone Dose (POD) for selected trees in regular mapping under the ETC/HE, following the earlier inclusion of the POD for crops. Maps of POD1 for tree species of beech (Fagus sylvatica) and spruce (Picea abies) have been prepared. POD calculation has been performed using routines earlier developed by INERIS and partly modified by CHMI. This tool follows the methodology described in the Manual for modelling and mapping critical loads and levels of the Air Convention (CLRTAP).
