Nitrogen upper atmosphere

Most CO and CO2 in the atmosphere contain the mass 12 isotope of carbon. However, due to the reaction of cosmic ray neutrons with nitrogen in the upper atmosphere, C is produced. Nuclear bomb explosions also produce C. The C is oxidized, first to CO and then to C02 by OH- radicals. As a result, all CO2 in the atmosphere contains some 0, currently a fraction of ca. 10 of all CO2. Since C is radioactive (j -emitter, 0.156 MeV, half-life of 5770 years), all atmospheric CO2 is slightly radioactive. Again, since atmospheric CO2 is the carbon source for photos5mthesis, aU biomass contains C and its level of radioactivity can be used to date the age of the biological material. 

The most abundant isotope is which constitutes almost 99% of the carbon in nature. About 1% of the carbon atoms are There are, however, small but significant differences in the relative abundance of the carbon isotopes in different carbon reservoirs. The differences in isotopic composition have proven to be an important tool when estimating exchange rates between the reservoirs. Isotopic variations are caused by fractionation processes (discussed below) and, for C, radioactive decay. Formation of takes place only in the upper atmosphere where neutrons generated by cosmic radiation react with nitrogen ... 

Meanwhile, Crutzen had done experiments showing that ozone in the upper atmosphere can be destroyed easily by reactions with nitrogen oxides. This work demonstrated that the ozone layer is in a delicate balance that could be disturbed significantly by changes in atmospheric composition. In 1974, Molina and Rowland combined Crutzen s experimental work with their own theoretical analysis and published a prediction (hypothesis) that CFCs pose a serious threat to the ozone layer. 

Photo-ionization of this sort is of profound importance in the upper atmosphere, where photons of vacuum UV light are absorbed and participate in reactions, e.g. with ozone and nitrogen oxides. These reactions help explain why the Earth s surface is relatively free of such harmful UV light, because the photons are absorbed en route through the Earth s atmosphere. 

Ammonium sulfate occurs in trace concentrations in the upper atmosphere. It is widely used as a fertilizer for rice and other crops. It is a source of sulfur for the soil. It is also used as an additive to supply nutrient nitrogen in fermentation processes (e.g., yeast production from molasses). It also is used for fireproofing timber and plastics, and in treatment of hides, and leather production. 

Ionization radiations also cause such combination, a process that occurs in the upper atmosphere forming oxides of nitrogen in low yields. 

Indeed, this happens every moment in the Earth s atmosphere. The upper atmosphere is bombarded with cosmic rays fast-moving subatomic particles produced by extremely energetic astrophysical processes such as nuclear fusion in the sun. When cosmic rays hit molecules in the atmosphere, they induce nuclear reactions that spit out neutrons. Some of these neutrons react with nitrogen atoms in air, converting them into a radioactive isotope of carbon carbon-14 or radiocarbon , with eight neutrons in each nucleus. This carbon reacts with oxygen to form carbon dioxide. About one in every million million carbon atoms in atmospheric carbon dioxide is C. 

In this way an equilibrium is maintained between the three forms of oxygen, O, 02 and 03. This equilibrium can be upset by chemical species which are carried to the upper atmosphere, specifically nitrogen oxides and chloro-fluorocarbons. 

Atoms with identical atomic numbers but different mass numbers are called isotopes, and the nucleus of a specific isotope is called a nuclide. There are 13 known isotopes of carbon, two of which occur commonly (12C and 13C) and one of which (14C) is produced in small amounts in the upper atmosphere by the action of neutrons from cosmic rays on 14N. The remaining 10 carbon isotopes have been produced artificially. Only the two commonly occurring ones are indefinitely stable the other 11 undergo spontaneous nuclear reactions, which change their nuclei. Carbon-14, for example, slowly decomposes to give nitrogen-14 plus an electron, a process we can write as... 

Radiocarbon dating of archaeological artifacts depends on the slow and constant production of radioactive carbon-14 in the upper atmosphere by neutron bombardment of nitrogen atoms. (The neutrons come from the bombardment of other atoms by cosmic rays.)... 

Ozone is a form of oxygen. Ozone is present in the upper atmosphere and it prevents dangerous solar radiation from reaching the Earth s surface. Some of the chemicals that diffuse into the upper atmosphere decompose ozone. Chemicals that have this effect are methane (CH4), chloromethane (CH3C/) and an oxide of nitrogen (N02). 

Tritium is formed in the upper atmosphere by bombardment of nitrogen, oxygen and carbon by high energy protons and by capture of cosmic-ray generated neutrons by nitrogen... 

Because radioactive isotopes seem to decay at very constant rates, they can be used as clocks. One of the first radioactive dating techniques involved the use of the radioisotope carbon-14. Carbon-14 is produced in the upper atmosphere when neutrons (produced by cosmic rays from space) collide with nitrogen-14 molecules in the reaction shown below ... 

Cosmic ray neutrons interact in the upper atmosphere with nitrogen, producing 15N, which is radioactive and disintegrates into common carbon (12C) and tritium ... 

Crutzen P.J., Gas-phase nitrogen and methane chemistry in the atmosphere. In Physics and Chemistry of the Upper Atmosphere, edited by B. McCormac, D. Reidel, Dordrecht, Netherlands (1973). 

Absorption of ultraviolet radiation by O3 causes it to decompose to O2. In the upper atmosphere, therefore, a steady-state concentration of ozone is achieved, a concentration ordinarily sufficient to provide significant ultraviolet protection of the Earth s surface. However, pollutants in the upper atmosphere such as nitrogen oxides (some of which occur in trace amounts naturally) from high-flying aircraft and chlorine atoms from photolytic decomposition of chlorofluorocarbons (from aerosols, refrigerants, and other sources) catalyze the decomposition of ozone. The overall processes governing the concentration of ozone in the atmosphere are extremely complex. The following reactions can be studied in the laboratory and are examples of the processes believed to be involved in the atmosphere ... 

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