Nuclear bomb tests, atmospheric

A mass of evidence seems to confirm that the mixing rate of radiocarbon in the atmosphere is rapid, and that with respect to its radiocarbon content the atmosphere can be considered as a homogeneous entirety. The contamination of samples with matter from an extraneous source can nevertheless invalidate this assumption. Two types of contamination can be differentiated physicochemical contamination and mechanical intrusion. There are two forms of physicochemical contamination. One is due to the dilution of the concentration of radiocarbon in the atmosphere by very old carbon, practically depleted of radiocarbon, released by the combustion of fossil fuel, such as coal and oil. The other is by the contamination with radiocarbon produced by nuclear bomb tests during the 1950s and later in the twentieth century. The uncertainties introduced by these forms of contamination complicate the interpretation of data obtained by the radiocarbon dating method and restrict its accuracy and the effective time range of dating. 

An anthropogenic addition of 14C into the atmosphere occurred with the nuclear bomb testing from 1952 to 1963, along with the introduction of bomb tritium. As a result, the 14C concentration also increased in plants (Fig. 11.2), in the soil C02, and in recharged groundwater. Values up to 200 pmc have been measured, but they decreased to about 120 pmc by 1987, and to about 110 pmc by 1995. 

Sr90 29.1 y synovial joints By-product of nuclear bomb testing in the atmosphere in the 1940s to 1960s... 

Actinides in the environment can be classified into two groups (i) the uranium and thorium series of radionuclides in the natural environment and (ii) neptunium, plutonium, americium and curium which are formed in a nuclear reactor during the neutron bombardment of uranium through a series of neutron capture and radioactive decay reactions. Transuranics thus produced have been spread widely in the atmosphere, geosphere and aquatic environment on the earth, as a result of nuclear bomb tests in the atmosphere, and accidental release from nuclear facilities (Sakanoue, 1987). Most of these radionuclide inventories have deposited in the northern hemisphere following the tests conducted by the United States and the Soviet Union. 

The global presence of radioactive fallout from the nuclear bomb tests of the 1950s and 1960s clearly illustrated the capacity of the atmosphere to distribute chemicals around Earth. Global transport has been demonstrated for a large number of chemicals that do not rapidly degrade or settle out of the atmosphere. Examples are methane (CH4), nitrous oxide (N20), and chloro-fluorocarbons (CFCs), all of which have half-lives in the atmosphere ranging from years to decades. 

Unintentional venting of an underground nuclear bomb test results in deposition of particles into the atmosphere at a height of 1.5 km over the site. If these soil particles have a density of 2.3 g/cm3, and the wind speed is 1.5 m/ sec, what would be the size of the particles that can be expected to fall predominantly outside the border of the test site, which is 200 km downwind ... 

Figure 6. Atmospheric concentrations as functions of the radiogenic noble gases Ar, Kr, and Kr and of the man made traces gases CFC-11, CFC-12, and SFe. Concentrations are normalized to the respective atmospheric abundances in 1998. In addition a typical (input) curve of in precipitation is shown. Note, nuclear bomb tests in the atmosphere increased the global tritium inventory by up a factor of 1000. Since then concentrations steadily decreased, but still today tritium activity in young meteoric waters is commonly one order of magnitude larger than the natural background due to cosmic rays production.

During the past fifty years, cesium acquired a very bad reputation on the basis of two of its radioactive isotopes - both of which have a relatively long physical half-life - being distributed throughout the Earth s atmosphere following nuclear bomb tests and/or accidents at nuclear power plants, especially at Chernobyl (IAEA, 1986). 

Gilbert ES, Tarone R, Bouville A, et al. Thyroid cancer rates and 1-131 doses from Nevada atmospheric nuclear bomb tests. J Natl Cancer Inst 1998 90 1654-1660. 

Material Flow Tracers are also used in studies of the flow of materials. Hydro-logic engineers use tracers to study the volume and flow of large bodies of water. By following radionuclides formed during atmospheric nuclear bomb tests ( H in H2O, and Cs" ), scientists have mapped the flow of water from land to... 

National Cancer Institute. (1997). Study estimating thyroid doses of 1-131 received by Americans from Nevada atmospheric nuclear bomb test. Retrieved March 7, 2009, from WWW. cancer, go v/i 131 /fallout/exesum. html... 

It has long been debated if and what role neurogenesis may play in the human brain. Recent data on estimation of human adult neurogenesis in the hippocampus were based on a technique employing radiocarbon dating to postmortem human brains [47]. This makes use of the atmospheric nuclear bomb testings that were banned in 1963 at least for the USA, GB, and the Soviet Union. The time period from 1945 to 1963 therefore introduced a pulse of into the plants and, subsequently, animals, and this... 

Atmospheric testing of nuclear bombs resulted in contamination of the surface of the ocean with various isotopes including H, °Sr, Pu, and " °Pu. These isotopes are slowly being mixed through the ocean... 

Nuclear bomb produced " 002 and (as HTO) have been used to describe and model this rapid thermocline ventilation (Ostlund et ah, 1974 Sarmiento et ah, 1982 Fine et al., 1983). For example, changes in the distributions of tritium (Rooth and Ostlund, 1972) in the western Atlantic between 1972 (GEOSECS) and 1981 (TTO) are shown in Fig. 10-10 (Ostlund and Fine, 1979 Baes and Mulholland, 1985). In the 10 years following the atmospheric bomb tests of the early 1960s, a massive penetration of F1 (tritium) into the thermocline has occurred at all depths. Comparison of the GEOSECS and TTO data, which have a 9 year time difference, clearly shows the rapid ventilation of the North Atlantic and the value of such transient" tracers. A similar transient effect can be seen in the penetrative distribution of manmade chlorofluorocarbons, which have been released over a longer period (40 years) (Gammon et al., 1982). 

Reference materials for radioisotopes have mainly been used for purposes relating to nuclear and radiation safety. Historically, the development of such materials first arose from the need to assess the risk to human populations caused by worldwide contamination of food and the environment as a consequence of atomic bomb testing - particularly from bombs exploded in the atmosphere. Even now, although atmospheric testing ceased many years ago, the residues from these tests still remain the main source of radionuclides such as Cs and °Sr in the global environment (though locally, other sources may be more important in some countries). 

In order to make use of this transient, the contributions of the natural and bomb radiocarbon had to be separated. Three sets of observations went into this separation. First, use was made of measurements on surface waters collected very early in the nuclear testing era (Broecker etal., 1960) and also with results of measurements on prenuclear growth ring-dated corals and mollusks (Drulfel and Linick, 1978 Drulfel, 1981, 1989). Second, use was made of the tritium released to the atmosphere during nuclear tests. As this bomb-test tritium swamped the natural tritium present in the ocean, the vertical distribution of tritium in the sea could be used to establish the limit of penetration of bomb radiocarbon. Finally, based on the radiocarbon analyses made on thermocline waters free of bomb tritium, it was shown that there was a close correlation between the natural ratio and the dissolved silica... 

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