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Air quality

What happens to air quality?

Large cities like Mexico, Beijing, Shanghai, New York, Johannesburg, etc., as well as the main industrial regions like the Ruhr Basin in Germany, the Benelux, the Po river valley in Italy stand out as severely polluted areas and are consequently clearly identifiable on air pollution maps, as seen for example in the mean global distribution of nitrogen dioxide (NO2) in the troposphere (see Figure 1).


Fig. 1: NO2 measurements in the troposphere (SCIAMACHY, 2004) (Credits: KNMI, BIRA-IASB, ESA)


However, next to emissions due to industrial activities, fossil fuel and biofuel use, it is worth noting that natural emissions also exist, for instance:

  • volcanic activity
  • sea salt
  • lightning strokes

Forest and savanna fires are also responsible for sometimes extremely large emissions of pollutants. These fires have to a large extent an anthropogenic origin : for example, deforestation and traditional agricultural practices (slash and burn) for fertilizing soils are clearly due to human activities, and it is estimated that purely natural fires (e.g. initiated by lightning) represent only a very small part of total emissions.

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