A. G. Megaritis

Impact of climate change on mercury concentrations and deposition in the eastern United States.

The global-regional climate-air pollution modeling system (GRE-CAPS) was applied over the eastern United States to study the impact of climate change on the concentration and deposition of atmospheric mercury. Summer and winter periods (300 days for each) were simulated, and the present-day model predictions (2000s) were compared to the future ones (2050s) assuming constant emissions. Climate change affects Hg(2+) concentrations in both periods. On average, atmospheric Hg(2+) levels are predicted to increase in the future by 3% in summer and 5% in winter respectively due to enhanced oxidation of Hg(0) under higher temperatures. The predicted concentration change of Hg(2+) was found to vary significantly in space due to regional-scale changes in precipitation, ranging from -30% to 30% during summer and -20% to 40% during winter. Particulate mercury, Hg(p) has a similar spatial response to climate change as Hg(2+), while Hg(0) levels are not predicted to change significantly. In both periods, the response of mercury deposition to climate change varies spatially with an average predicted increase of 6% during summer and 4% during winter. During summer, deposition increases are predicted mostly in the western parts of the domain while mercury deposition is predicted to decrease in the Northeast and also in many areas in the Midwest and Southeast. During winter mercury deposition is predicted to change from -30% to 50% mainly due to the changes in rainfall and the corresponding changes in wet deposition.

Sensitivity of Fine PM Levels in Europe to Emissions Changes

A three-dimensional chemical transport model (CTM), PMCAMx-2008, was applied to Europe to study the influence of emissions changes on fine PM levels. Various emissions scenarios were studied, covering summer and winter periods to quantify also the seasonal variation. Reduction of NH3 emissions seems to be the most effective control strategy for reducing PM2.5 over Europe, in both seasons, mainly due to reduction of NH4NO3. A reduction of SO2 emissions has a significant effect on PM2.5 levels over the Balkans during summer, due to decrease of sulfate, while the reduction of anthropogenic OA emissions has a strong effect on total OA mainly in areas close to emissions sources. The NOx emissions control strategy seems to be problematic in both seasons. Our analysis in European Megacities, based on a scenario zeroing all anthropogenic emissions, showed that the contribution of local emissions on total PM2.5, depends on the chemical component, with local sources being especially important mainly for black carbon (BC).

Emissions of Megacities and Their Impact on Air Quality Over Europe

PMCAMx-2008, a three dimensional chemical transport model (CTM) was applied in Europe, to quantify the influence of emissions in European Megacities (Paris, London, Rhine-Ruhr, Po Valley) on the concentration of the major PM2.5 components. Different emissions scenarios were applied (e.g. an “annihilation” scenario zeroing all anthropogenic emissions in Megacities), and the impact of Megacities emissions on air quality within Megacities and also in the surrounding regions was investigated. Two simulation periods were used, summer 2009 and winter 2010, to study the seasonal effect of Megacities emissions. The results show that the impact of the local emissions on the concentration of total PM2.5 within Megacities is in the 10–60% range during wintertime depending on the chemical component and in the 5–40% range during summer. Local sources are especially important for black carbon (BC) contributing more than 40% of its concentration within Megacities, during both periods (up to 90% in Po Valley). Megacities emissions also influence the air quality of the surrounding regions within an average radius of 250 km from the Megacity.

A study concerning splitting and jointly continuous topologies on C(Y,Z)

Abstract Let Y and Z be two fixed topological spaces and C(Y, Z) the set of all continuous maps from Y into Z. We construct and study topologies on C(Y, Z) that we call Fn(τn)-family-open topologies. Furthermore, we find necessary and sufficient conditions such that these topologies to be splitting and jointly continuous. Finally, we present questions concerning a further study on this area.

Simulating Organic Aerosol Over Europe: Concentration, Chemical Composition and Sources

PMCAMx-2008, a detailed three-dimensional chemical transport model, was applied for the first time in Europe to simulate fine organic aerosol concen-trations during the months of May 2008, February 2009, July 2009 and January 2010. The model includes a state-of-the-art organic aerosol module which is based on the volatility basis set framework treating both primary and secondary organic components as semivolatile and photochemically reactive. The model predicts that fresh primary OA (POA) is a small contributor to organic PM concentrations in Europe during the summer and spring, and that oxygenated species (oxidized primary and biogenic secondary) dominate the ambient OA. During the winter model results suggest a significant underestimation of OA emissions from wood burning. Use of very high resolution emissions inventory does not result in a significant improvement of the predictions of the model over the Megacity of Paris.