| Περίληψη: | The scope of this dissertation was to enhance our knowledge regarding the potential effects that emissions and climate change could have on air pollutants (e.g., particulate matter, ozone, Hg), in order to design effective strategies for improving air quality.
A 3-D chemical transport model, PMCAMx-2008, was applied over Europe to evaluate the response of PM2.5 to 50% reduction in emissions of precursor gases (SO2, NH3, NOx, VOCs) and anthropogenic primary OA (POA). A summer and a winter simulation period were used, to investigate also the seasonal dependence of the PM2.5 response to emissions changes. Reduction of NH3 emissions seems to be the most effective control strategy for reducing PM2.5, in both periods, resulting in a decrease of PM2.5 up to 5.1 μg m-3 and 1.8 μg m-3 during summer and winter respectively. The SO2 reduction is more effective during summer, especially over Balkans. The anthropogenic POA control strategy reduces total OA, in both periods, mainly in urban areas close to its emissions sources. The reduction of NOx emissions reduces PM2.5 during the summer period, causing although an increase of ozone (O3) concentration in major urban areas and over Western Europe. Additionally, the NOx control strategy actually increases PM2.5 levels during the winter period.
PMCAMx-2008 was also applied over Europe, to quantify the individual effects of the major meteorological parameters on PM2.5 levels. Our simulations cover three periods, representative of different seasons (summer, winter, and fall). PM2.5 appears to be more sensitive to temperature changes compared to the rest meteorological parameters in all seasons. PM2.5 generally decreases as temperature increases, although the predicted response is spatially variable, ranging from -8% K-1 to 7% K-1. The predicted responses of PM2.5 to absolute humidity are also quite variable, ranging from -1.6% %-1 to 1.6% %-1. A decrease of wind speed (keeping constant the emissions), increases all PM2.5 species due to changes in dry deposition (approximately 10%) and dispersion. In addition, the wind speed effects only on sea salt emissions could be significant for PM2.5 concentrations in coastal areas. Increases in precipitation have a negative effect on PM2.5 due to increases in wet deposition. Regarding the relative importance of each of the meteorological parameters in a changed future climate, the projected precipitation changes are expected to have the largest impact on PM2.5 levels, with changes up to 2 μg m-3.
PMCAMx-2008 was used as part of the GRE-CAPS modeling system, to investigate the effects of climate change on PM2.5 and O3 levels in Greece. Summertime periods are simulated both for the present (2000s) and the future (2050s). Our results suggest that climate change will generally decrease PM2.5 in Greece, by 1.1 μg m-3 (5%) on average. However the predicted changes are quite variable in space, ranging from -20% to 20%. Higher levels of O3 are predicted in the future over Greece (4.5% on average). The higher future temperatures determine to a large extent the predicted O3 response
Finally, the GRE-CAPS was applied over the eastern United States to study the impact of climate change on the concentration and deposition of mercury. Summer and winter periods (300 days for each) are simulated, and the present-day model predictions (2000s) are compared to the future ones (2050s). On average, atmospheric Hg2+ levels are predicted to increase in the future by 3% in the summer and 5% in winter respectively. However, the predicted concentration changes of Hg2+ vary significantly in space, ranging from -20% to 40%. Particulate mercury, Hg(p) has a similar spatial response to climate change as Hg2+, while Hg0 levels are not predicted to change significantly. Mercury deposition is also predicted to change in the future, with variable changes, ranging from -50% to 50%. The predicted response is mainly attributed to the spatially variable changes of rainfall in the future and the accompanying changes in mercury wet deposition.
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