Estimation of the Wheat Losses Caused by the Tropospheric Ozone in Bulgaria and Denmark

Long-term exposures to high ozone concentrations have harmful effect on the crops and reduce the yield. The exposures are measured in terms of AOT40 (Accumulated exposure Over Threshold of 40 ppb). The threshold of 40 ppb has been accepted after several years of experimental research in open top chambers throughout Europe. As a result of these experiments a critical level of 3000 ppb.hours has been established for the crops. The sensitivity of the wheat to exposures above the critical level has been studied in more detail and a linear dependence between the relative yield and the AOT40 has been found. This relationship is used in the paper to estimate the wheat losses in Bulgaria and Denmark by regions in several consequtive years. The Danish Eulerian Model is used to calculate the AOT40 values on the EMEP grid (a 96×96 square grid with step 50 km., which covers Europe). The results on parts of this grid (covering Bulgaria and Denmark) are only used. In addition regional information about the actual yield and the prices is also needed for the target years. The algorithm for economical evaluation of the losses can be applied with different scenarios for partial reduction of the emissions and some other key parameters. The results can be used as a ground for a cost-benefit analysis of possible ozone reduction measures when effects on vegetation are studied.