Pollution chlorofluorocarbons

It is the use of LIDAR devices as tools for spectroscopic measurements on the various gases present in the atmosphere which concerns us here. These include ozone, carbon dioxide, the CFCs (chlorofluorocarbons, such as CFC-11, trichlorofluoromethane, and CFC-12, dichlorodifluoromethane, used as refrigerants) and all those molecules regarded as atmospheric pollutants. 

Air pollution (qv) problems are characteri2ed by their scale and the types of pollutants involved. Pollutants are classified as being either primary, that is emitted direcdy, or secondary, ie, formed in the atmosphere through chemical or physical processes. Examples of primary pollutants are carbon monoxide [630-08-0] (qv), CO, lead [7439-92-1] (qv), Pb, chlorofluorocarbons, and many toxic compounds. Notable secondary pollutants include o2one [10028-15-6] (qv), O, which is formed in the troposphere by reactions of nitrogen oxides (NO ) and reactive organic gases (ROG), and sulfuric and nitric acids. 

An important effect of air pollution on the atmosphere is change in spectral transmission. The spectral regions of greatest concern are the ultraviolet and the visible. Changes in ultraviolet radiation have demonstrable adverse effects e.g., a decrease in the stratospheric ozone layer permits harmful UV radiation to penetrate to the surface of the earth. Excessive exposure to UV radiation results in increases in skin cancer and cataracts. The worldwide effort to reduce the release of stratospheric ozone-depleting chemicals such as chlorofluorocarbons is directed toward reducing this increased risk of skin cancer and cataracts for future generations. 

The temperature inversion at the tropopause prevents mixing between the stratosphere and troposphere, with hotter air (less dense) sitting on top of cooler air (more dense). Pollutants (such as chlorofluorocarbons) present in the stratosphere have very long lifetimes (of order 30 years) and become persistent problems, especially... 

Terrence Collins is the Thomas Lord Professor of Chemistry at Carnegie Mellon University who contends that the dangers of chlorine chemistry are not adequately addressed by either academe or industry, and alternatives to chlorine and chlorine processors must be pursued. He notes, Many serious pollution episodes are attributable to chlorine products and processes. This information also belongs in chemistry courses to help avoid related mistakes. Examples include dioxin-contaminated 2,4,5-T, extensively used as a peacetime herbicide and as a component of the Vietnam War s agent orange chlorofluorocarbons (CFCs) polychlorinated biphenyls (PCBs the pesticides aldrin, chlordane, dieldrin, DDT, endrin, heptachlor, hexachlorobenzene, lindane, mirex, and toxaphene pentachlorophe-... 

The different greenhouse gases can have complicated interactions. Carbon dioxide may cool the stratosphere which slows the process that destroys ozone. Stratospheric cooling can also create high altitude clouds which interact with chlorofluorocarbons to destroy ozone. Methane may be produced or destroyed in the lower atmosphere at various rates, which depend on the pollutants that are present. Methane can also affect chemicals that control ozone formation. 

For example, Brennan (1993) argues that the answer to chlorofluorocarbon (CFC) pollution is not a suit against all the users of spray cans and refrigerators. 

The half-life, tm, of a substance is the time needed for its concentration to fall to one-half its initial value. The half-lives of pollutants such as chlorofluorocarbons are important for assessing their environmental impact. If their half-lives are short, they may not survive long enough to reach the stratosphere, where they can destroy ozone. 

Some halogen compounds have been too reactive for the health of people and the planet. They can destroy healthy cells and attack the Earths atmosphere in the same active way that they kill germs or break down wood into paper. For instance, chlorofluorocarbon (or CFC) compounds used to be popular cooling chemicals in refrigerators and air conditioners and in the gas that pushed hairspray and deodorant out of aerosol cans. CFCs are now widely banned because they destroy Earths atmosphere. Chlorine is also part of the insect killer DDT, a dry cleaning fluid, and the compounds called PCBs. All of these products are now banned or used rarely because they have been linked to pollution and health problems like cancer and liver disease. 

A number of compressed and liquified gases are used as refrigerants and aerosol propellants. These include nitrous oxide, nitrogen, carbon dioxide, propane, and butane. The use of chlorofluorocarbons (CFCs) is restricted because of environmental pollution leading to health hazards. These have been replaced by hydrogenated fluorocarbons (HFCs), which are less likely to cause environmental pollution. 

This section is devoted to the application of cathodic reduction for treating aliphatic and aromatic pollutants at low concentrations, and also to the dechlorination of chlorofluorocarbons (CFCs) in aqueous media. The... 

Chlorofluorocarbons (CFCs) are an important class of polluting gases that are not usually caused by burning fossil fuels. CFCs are stable and harmless near the ground. When they make their way up into the atmosphere, however, they interact and interfere with atmospheric processes. In particular, these gases interfere with the production and reactions of ozone, 03. You will learn more about CFCs later in this section. 

States would spend 160 billion per year on pollution control. In 1996 Ben Lieberman, an environmental research associate with the Competitive Enterprise Institute, estimated that in the United States the cost of the phaseout of chlorofluorocarbons (CFCs) in accordance with the 1987 Montreal Protocol on Substances That Deplete the Ozone Layer could reach 100 billion over the next ten years. Indeed chemical manufacturers had to develop eco-friendly substitutes such as hydrochlorofluorocarbon (HCFC) and hydro-fluorocarbon (HFC), which are more costly to make, and hundreds of millions of pieces of air-conditioning and refrigeration equipment using CFCs had to be discarded. 

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