Increases in Wintertime Oxidation Capacity Counteract the Success of Emission Reduction Measures in Europe with Respect to Secondary Inorganic Aerosols

Air pollution reduction measures in Europe have led to marked decreases in the levels of primary pollutants such as SO2 and NOx since the 1980s while for secondary pollutants like ozone and secondary inorganic aerosols (SIA) the effects of these measures are much less obvious. A recent extensive comparison of the composition of particulate matter smaller than 10 μm (PM10) in Switzerland between the years 1998/1999 and 2008/2009, for example, revealed no changes in the levels of nitrates despite large NOx emission reductions over this period. Similarly, aerosol sulphates decreased much less strongly than the precursor gas SO2.