The ozone layer
Ozone is present in the atmosphere from the ground up to 50 km altitude and higher. However, most of the ozone is in a region of the atmosphere called the stratosphere, which extends roughly from 10 to 50 km above the surface of the Earth. In the stratosphere, the maximum ozone amount can be found between 20 and 25 km above the surface of the Earth. This ozone rich region is commonly called the "ozone layer". Ozone in the stratosphere has a beneficial role as it blocks UV radiation from the sun. The troposphere contains only about 10 % of the total ozone amount and can be divided into two layers. The lowermost part is called the Planetary Boundary Layer (PBL), extending upward from the surface to a height that ranges between 100 and 3000 m. Above this layer we have the free troposphere. High ozone levels in the boundary layer can have adverse impacts on human health and on the health of animals and vegetation. Ozone is photochemically formed by the interaction between NOx- (Nitrogen oxides) and VOC's (Volatile Organic Compounds) components. In situ photochemistry and transport from other regions can lead to very high ozone concentrations, referred as SMOG ozone. More information on the formation of SMOG ozone can be found on the website of the European environment Agency . The ozone concentrations for Belgium are continuously measured and are hourly updated by the interregional cell for the environment Ircel-Celine . Also other pollutants can be consulted.
Ozone distribution as a function of altitude.