Krypton atmospheric abundance

Krypton is produced in nuclear fi ssion, and its atmospheric abundance is a measure of worldwide nuclear activity. Krypton is found in the atmosphere with a concentration of about 1 ppm. 

Bogard D. D. and Garrison D. H. (1998). Relative abundances of argon, krypton, and xenon in the Martian atmosphere as measured in Martian meteorites. Geochimica et Cosmochimica Acta, 62(10) 1829-1835. 

Krypton is the 81st most abundant element on Earth and ranks seventh in abundance of the gases that make up Earths atmosphere. It ranks just above methane (CH ) in abundance in the atmosphere. Krypton is expensive to produce and thus has hmited use. The gas is captured commercially by fractional distillation of liquid air. Krypton shows up as an impurity in the residue. Along with some other gases, it is removed by filtering through activated charcoal and titanium. 

Noble gases may provide a constraint on the source of water and other volatiles. The abundance pattern of noble gases in planetary atmospheres resembles that of chondrites, perhaps arguing against comets. However, there are some differences, especially in the abundance of xenon. Relative to solar system abundances, krypton is more depleted than xenon in chondrites, but in the planets, krypton and xenon are present in essentially solar relative abundances (Fig. 10.11). This observation has been used to support comets as the preferred source of volatiles (even though measurements of xenon and krypton in comets are lacking). A counter-argument is that the Ar/H20 ratio in comets (if the few available measurements are accurate and representative) limits the cometary addition of volatiles to the Earth to only about 1%. 

Helium is the second most abundant element in the universe. In the Earth, it is continuously formed by radioactive decay, mostly of uranium and thorium. Its present concentration in the atmosphere is probably the equilibrium concentration between the amount being released from the Earth s crust and the amount of hehum escaping from the atmosphere into space. The atmosphere represents the major source for neon, argon, krypton, and xenon. They are produced as by-products during flactional distillation of liquid air. Radon is obtained from the radioactive decay of radium. 

For most of the chemical elements, the relative abundances of their stable isotopes in the Sun and solar nebula are well known, so that any departures from those values that may be found in meteorites and planetary materials can then be interpreted in terms of planet-forming processes. This is best illustrated for the noble gases neon, argon, krypton, and xenon. The solar isotopic abundances are known through laboratory mass-spectrometric analysis of solar wind extracted from lunar soils (Eberhardt et al., 1970) and gas-rich meteorites. Noble gases in other meteorites and in the atmospheres of Earth and Mars show many substantial differences from the solar composition, due to a variety of nonsolar processes, e.g., excesses of " Ar and... 

Besides their presence due to in situ radioactive decay within a given solid sample, radiogenic " He, " Ar, Xe, Pu-fission xenon (and krypton), and likely also U-fission xenon, are also prominent or observable constituents of planetary atmospheres, and their abundance is important in constraining models for planetary atmosphere evolution (see Chapter 4.12). 

Noble gases and nitrogen in martian meteorites reveal several interior components having isotopic compositions different from those of the atmosphere. Xenon, krypton, and probably argon in the mantle components have solar isotopic compositions, rather than those measured in chondrites. However, ratios of these noble gas abundances are strongly fractionated relative to solar abundances. This decoupling of elemental and isotopic fractionation is not understood. The interior ratio in martian meteorites is similar to chondrites. 

The abundance of krypton in the atmosphere is thought to be about 0.000108 to 0.000114 percent. The element is also formed in Earth s crust when uranium and other radioactive elements break down. The amount in Earth s cmst is too small to estimate, however. 

Oxygen is the most abundant substance in the universe. Krypton and xenon are so rare as almost to leave doubts as to their existence. Methane is practically insoluble in water. Ammonia is absorbed to the extent of 1,000 times the volume of water. Chlorine may be liquefied and solidified with very meager pressures, and at atmospheric temperature. It is doubtful if hydrogen or methane have ever been even liquified, certainly not without the most extreme conditions of pressure and refrigeration. 

The Group 8A(18) elements are helium (He, the second most abundant element in the universe), neon (Ne), argon (Ar, which makes up about 0.93% of Earth s atmosphere), krypton (Kr), xenon (Xe), and radioactive radon (Rn). Only the last three form compounds [Group 8A(18) Family Portrait]. 

Argon is the most abundant noble gas it comprises about 0.93 percent of the atmosphere. Helium, neon, and krypton (Kr) can all be found in air as well, and they can be isolated using fractional distillation of liquid air, except for helium. 

The principal source of the noble gases is the atmosphere. Table 7.1 shows the nine most plentiful components of the atmosphere by mass. Over 98% is nitrogen and oxygen, but the noble gas argon comes third, making up over half the residue. It is therefore more abundant than water vapour, and much more abundant than CO2. Trailing far behind carbon dioxide, come neon, krypton, helium and xenon in that order. 

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