Response of fine particulate matter concentrations to changes of emissions and temperature in Europe

Abstract. PMCAMx-2008, a three dimensional chemical transport model (CTM), was applied in Europe to quantify the changes in fine particle (PM_2.5) concentration in response to different emission reductions as well as to temperature increase. A summer and a winter simulation period were used, to investigate the seasonal dependence of the PM_2.5 response to 50% reductions of sulfur dioxide (SO₂), ammonia (NH₃), nitrogen oxides (NO_x), anthropogenic volatile organic compounds (VOCs) and anthropogenic primary organic aerosol (POA) emissions and also to temperature increases of 2.5 and 5 K. Reduction of NH₃ emissions seems to be the most effective control strategy for reducing PM_2.5, in both periods, resulting in a decrease of PM_2.5 up to 5.1 μg m⁻³ and 1.8 μg m⁻³ (5.5% and 4% on average) during summer and winter respectively, mainly due to reduction of ammonium nitrate (NH₄NO₃) (20% on average in both periods). The reduction of SO₂ emissions decreases PM_2.5 in both periods having a significant effect over the Balkans (up to 1.6 μg m⁻³) during the modeled summer period, mainly due to decrease of sulfate (34% on average over the Balkans). The anthropogenic POA control strategy reduces total OA by 15% during the modeled winter period and 8% in the summer period. The reduction of total OA is higher in urban areas close to its emissions sources. A slight decrease of OA (8% in the modeled summer period and 4% in the modeled winter period) is also predicted after a 50% reduction of VOCs emissions due to the decrease of anthropogenic SOA. The reduction of NO_x emissions reduces PM_2.5 (up to 3.4 μg m⁻³) during the summer period, due to a decrease of NH₄NO₃, causing although an increase of ozone concentration in major urban areas and over Western Europe. Additionally, the NO_x control strategy actually increases PM_2.5 levels during the winter period, due to more oxidants becoming available to react with SO₂ and VOCs. The increase of temperature results in a decrease of PM_2.5 in both periods over Central Europe, mainly due to a decrease of NH₄NO₃ during summer (18%) and fresh POA during wintertime (35%). Significant increases of OA are predicted during the summer due mainly to the increase of biogenic VOC emissions. On the contrary, OA is predicted to decrease in the modeled winter period due to the dominance of fresh POA reduction and the small biogenic SOA contribution to OA. The resulting increase of oxidant levels from the temperature rise lead to an increase of sulfate levels in both periods, mainly over North Europe and the Atlantic Ocean. The substantial reduction of PM_2.5 components due to emissions reductions of their precursors outlines the importance of emissions for improving air quality, while the sensitivity of PM_2.5 concentrations to temperature changes indicate that climate interactions need to be considered when predicting future levels of PM, with different net effects in different parts of Europe.