Ozone pollution

In our atmosphere ozone is a positive or negative layer depending on where it is found. Depending upon the distance above the planet's surface the atmosphere of the earth is divided into four layers, with ozone important in the two levels - the stratosphere and the troposphere. The level that contain the air we breath, ozone is a damaging pollutant in the troposphere. The stratosphere which lies 15-50 km above the ground contains a protective layer of ozone which filters out the harmful rays of the sun.

Ozone(o3) occurs naturally in the lowest layer of our atmosphere i.e troposphere and the second layer of the atmosphere i.e. stratosphere. Tropospheric ozone is also considered as a greenhouse gas contributing to global warming.

When volatile organic pollutants such as hydrocarbons react in the atmosphere to form oxygenated products such as aldhydes, the problem occurs.Oxygen in these molecules allows NO to form NO2, without breaking down ozone, thus ozone accumulates. The ozone build-up therefore depends upon the realtive concentrations of nitrogen oxides, hydrocarbons and other pollutants, and sunlight. It takes time for the ozone to accumulate as the chemical reactions involved are little slow ozone builds up in polluted air masses. This takes several days and is favoured by low windspeeds and prolonged sunnny weather. Polluted air masses often come from continental Europe, therefore ozone episodes are more frequent in southern England.