Explain briefly why the troposphere and the stratosphere are impacted by air pollution
Answers
Ozone (O3) is a reactive gas that exists in two layers of the atmosphere: the stratosphere (upper layer) and the troposphere (at ground level and up to 15km).
In the stratosphere, ozone protects life on Earth from the sun’s ultraviolet radiation. In contrast, at lower levels, it is an important greenhouse gas and air pollutant, which is harmful to human and ecosystem health. It is also a major component of urban smog.
Tropospheric ozone is a short-lived climate pollutant with an atmospheric lifetime of hours to weeks. It does not have any direct emissions sources, rather it is a secondary gas formed by the interaction of sunlight with hydrocarbons – including methane – and nitrogen oxides, which are emitted by vehicles, fossil fuel power plants, and other man-made sources.
Strategies to prevent the formation of tropospheric ozone are primarily based on methane reductions and cutting the levels of atmospheric pollution arising from man-made sources, such as agriculture and fossil fuel production and distribution.
In the troposphere, ozone is the product of the atmospheric reaction of a number of precursor pollutants, which have both natural and man-made sources. Precursor pollutants created by human activities include hydrocarbons and nitrogen oxides, which are largely emitted by cars and other vehicles, fossil fuel power plants, oil refineries, the agriculture sector and a number of other industries.
Ozone absorbs radiation and consequently acts as a strong greenhouse gas. Tropospheric ozone affects the climate beyond increased warming, having impacts on evaporation rates, cloud formation, precipitation levels, and atmospheric circulation. These impacts mainly occur within the regions where tropospheric ozone precursors are emitted, and so disproportionally affect the Northern Hemisphere.