Air Pollution
What is Air Pollution?
Air pollution is the build up of gases or aerosol particles emitted by human activities to levels that cause damage to plants, animals or ecosystems. The state of air pollution is often expressed as Air Quality, which is a measure of the concentrations of gaseous pollutants and size or number of particulate matter.
Some of the major trace gases that man-made activities have perturbed from their natural state are carbon monoxide (CO), Volatile Organic Compounds (VOCs), SO2 and nitrogen oxides (NOx); NO and NO2. Nitrogen oxides and VOCs react together to form ozone (O3), a major constituent of smog. In GEOMON we are monitoring changes in NO2, CO and O3 in order to study how they have changed across Europe, geographically and with time, over the last 3 decades.
Trends in Pollutants
Direct emissions of CO and NO2 across Europe have dropped markedly over the last 20 years due to the introduction of catalytic convertors in cars and cleaner industrial practices and this can be seen from the emission inventories as shown in Figure 1. However, the story of emissions from outside of Europe is another matter and rising emissions in South East Asia for example has lead to a global increase in emissions. These species are also known as trans-boundary pollutants and are not just present close to their source, so lowering local emissions does help to a certain extent but rising global levels lead to an increasing “background” of these trace gases.
GEOmon research on Air Pollution
Research on the GEOMON project has shown that the baseline trace gases at many European sites is actually increasing but the incidences of pollution peaks (caused by local events) is on the decrease. The major emission reductions occurred in Europe over 10 years ago, and thus the reductions in NO2 and O3 are levelling off in many areas but not everywhere. Representativeness studies in GEOMON for each of over 30 European monitoring stations reveals that some sites are more affected by local sources than background levels and Figure 2 shows how from 1996-2005 ozone has decreased to varying degrees at these stations.
Links with other atmospheric issues: Greenhouse gases and the stratosphere
Air pollution contributes towards global warming, particularly ozone (a significant greenhouse gas and also an indirect controller of greenhouse gas lifetimes) so keeping ozone levels as low as possible implicates in both air quality and climate change policies.. Most people will be more familiar with ozone as constituting the ozone layer (see stratospheric science section here) but actually even though the ozone molecule is the same, where it is formed is important and ground level ozone cannot be transported up to fill the ozone layer hole. There is some exchange between the two layers but the science questions remain separate.
GEOMON and trace gas monitoring
GEOMON scientists from Switzerland, the UK, Germany, Norway, The Netherlands, Belgium and France have been working on measuring and analysing trace gas levels around Europe, from ground level monitoring stations (e.g. The Jungfraujoch high Alpine station in Figure 3), from instrumentation that measure their levels in a profile through the lower atmosphere (Figure 4), from aircraft measurements (Figure 5) and from satellite measurements and the use of the profile measurements to validate satellite data.
GEOmon Achievements in Scientific Understanding of Air Pollution
GEOMON has brought together measurement techniques from a variety of sources and has inter-compared these in order to create a more comprehensive picture of long term changes and geographical distribution of trace gases. The long term aim is to integrate these many databases and timeseries and develop tools for statistical analysis of the data. A harmonised dataset of over 100 sites will be available to the public and policy makers to show the evolution of trace gas levels across Europe.
