Assessing the efficiency of different mitigation strategies to reduce shipping related airpollution levels and exposure in the Mediterranean coastal region – An ensemble modelling approach

The air quality in the Mediterranean coastal region is adversely affected by rising shipping emissions in the area. The present study demonstrates the results of an ensemble modelling approach for assessing the impact of shipping emissions on current and future air quality concentrations and exposure in the coastal Mediterranean region. Ensemble model means were calculated based on the results of three regional or global dispersion models (EMEP, SILAM and CMAQ) to simulate annual and seasonal atmospheric pollutant dispersion patterns in the Mediterranean region, under the baseline scenario and two selected 2050 future scenarios developed within the EMERGE (Evaluation, control and Mitigation of the EnviRonmental impacts of shipping Emissions) project. The selected scenarios examine the impact of a) the designation of a Mediterranean Sulphur/Nitrogen Emission Control Area (SECA/NECA) and the extensive use of open-loop scrubbers, exhaust gas cleaning systems and Selective Catalytic Reduction systems on future shipping emissions (Scenario 3- S3) and b) the increased use of methane and methanol as alternative fuels in 2050 (Scenario 8 - S8). Ensemble model results were combined with population data for calculating population weighted concentrations of legislated atmospheric pollutants for 30 Mediterranean coastal cities, representing exposure of city inhabitants to current and predicted future air pollution levels. The findings of the present study reveal significant annual city average reductions of SO2 and PM2.5 shipping related exposure for both S3 (89.78% reduction) and S8 (96.22% reduction), while shipping induced NO2 city-average exposure levels were efficiently controlled in S3 (42.74%) but not in S8 (4.39%). The reported results need to be specifically considered in the development of policy recommendations on shipping emission control for the Mediterranean region.