| Atmospheric Pollution |
| Nearly all Atmospheric pollutants occur naturally with the exception of chloroflourocarbons (CFCs). The major atmospheric pollutants will be mentioned here and their impact beginning with carbon dioxide. Carbon Dioxide The present contration of carbon dioxide is estimated at 302 ppm (parts per million). this level may reach as much as 600 ppm by 2065 dependent on the future rate of fossil fuel consumption and the way carbon dioxide is absorbed by the oceans. The world's oceans provides and sink for carbon dioxide. The ability of an ocean to absorb carbon dioxide depends on it's warmth. The warmer the ocean is, the it's absorptive capacity. The oceans are likely to become much warmer (if global warming is as pronounced as it is being made to seem). Warmer oceans will be able to absorb more carbon dioxode and will grow in size due to addition of water by melting ice caps. The burning of fossil fuels is an important source of atmospheric carbon dioxide. In 1981 alone an estimated 5.3 gigatons of carbon dioxide was released in to the atmosphere.An estimated 160 gigatons of carbon dioxide was emitted into the atmosphere from 1950 to 1981. Rate of carbon dioxide emission is expected to fall due to the use of alternative fuels and greater environmental awareness. Another important source of carbon dioxide is deforestation by burnining forests. There are indications that deforestation has surpassed fossil fuel burning as a source of caron dioxide emission. Deforestation is estimated to produce about 6 gigatons of carbon dioxide yearly. There is uncertainty about the rate of deforestation and the proportion that occurs by burning. It is also uncertain how much carbon is kept stored as charcoal and how much carbon dioxide vegetation regrowth consumes. Carbon dioxide levels in the atmosphere affect the global heat balance because it is virtually transparent to incoming short wave radiation but absorbs a lot of outgoing long wave radiation. This leads to rising temperatures in the lower atmosphere and the surface (the green house effect). Surface temperatures have increased by about 0.5 degrees (celcius) in this century. This very significant as the difference between now and the last ice age was only 3.5 degrees. Methane Methane has a high capacity to absorb radiation in the 7.66 micrometer band. The atmospheric concentraton of methane rose from about 600 ppb (parts per billion) to about 1300 ppb between 1700 and 1900. In 1983 atmospheric methane concentration reached 1600 ppb. The main sources of of these increases is the increased cultivation of wet (paddy) rice, the imperic fermentation in the intestines of domestic cattle and hogs and the burning of fossil fuels. CFC's CFC's are the only gaseous pollutants that don't occur naturally. They are important greenhouse gases because their effect is great in relatively small amounts. They not only contribute to the greenhouse effect but also to stratospheric ozone depletion. More on CFC's later. Nitrous Oxide Nitrous Oxide is produced primarily from the burning of carbons, the use of ammonia based fertilisers, deforestation (by burning) and the burning of biomass. It is of relatively low importance as a greenhouse gas. Krypton There are several types of krypton. The one that we are concerned about is krypton 85. It is emitted largely from nuclear reactors. It's increased prescence in the atmosphere reduces the electric resistance between the oceans and the ionosphere. This affects the electrical capacity of thunderclouds and by extension, the level of precipitation. Water Vapour Water vapour affects the natural balance between the stratosphere and the troposphere. More later |