ChArMEx

Context and objective

As the historical cradle of many civilisations, the Mediterranean is a region of major geostrategic interest with considerable environmental, political and societal challenges. However, it is a very vulnerable region whose future habitability could be compromised. One of the main sources of concern is the degradation of air quality and the possible positive feedback of this pollution on the regional climate and vice versa.

It is a little-known fact that the air is often more polluted in the middle of the Mediterranean than in the suburbs of Europe’s major cities, particularly in summer, the season in which peaks in gas and particle pollution traditionally develop. And although this pollution is partly due to the activities of the 470 million or so people living along the coast, it is above all a product of imports. The reason is simple. Located at the confluence of several natural spillways that drain the air from neighbouring continents (Europe to the north and Africa to the south), the Mediterranean is the receptacle of all types of pollution. This pollution, which converges over the basin, particularly the western basin, which is surrounded on all sides by high relief, can be :

• Pollution due to man-made emissions coming from the north and flowing into the basin via the major river valleys (Rhone, Po);
• natural pollution from the Sahara in the form of gigantic plumes of desert dust
• Pollution from around the basin due to forest fires or to plant ecosystems that emit organic compounds under the effect of thermal and hydric stress.
• Furthermore, under the effect of the hot, sunny and dry Mediterranean climate, this pollution will become more harmful due to the formation of ozone and ultrafine dust (in particular organic aerosols known as AOS for secondary organic aerosols) likely to cause respiratory and cardiovascular problems but also to modify the climate by causing more drought: the beginning of a vicious circle.

The ChArMEx programme, which was part of the MISTRALS (Mediterranean integrated studies at regional and local scales) meta-programme, aimed to better characterise atmospheric pollution in the Mediterranean basin and its surroundings in order to identify its sources, aggravating factors and consequences on the environment in the near and long term. To this end, the measurement resources of the observatories already in place in the Mediterranean have been strengthened, while new observatories have been created, particularly in the western basin where there were none, in order to monitor the evolution of atmospheric composition over the long term. In parallel, intensive measurement campaigns are organised during the summer (peak pollution season). The 2013 campaign thus followed a pre-campaign that took place in 2012 and was followed in 2014 by several smaller campaigns.

This was the first time that scientists, public authorities and industry agreed on a regulatory protocol to protect the environment.