Information AboutRadiocarbon |
| CATEGORIES ABOUT CARBON-14 | |
| isotopes of carbon | |
| environmental isotopes | |
Carbon-14, '''14C''', or '''radiocarbon''', is a Radioactive Isotope of Carbon discovered on February 27 , 1940 , by Martin Kamen and Sam Ruben . Its Nucleus contains 6 Protons and 8 Neutrons . Its presence in organic materials is used extensively as basis of the Radiocarbon Dating method to date archaeological, geological, and hydrogeological samples. There are three naturally occurring isotopes of carbon on Earth: 99% of the carbon is Carbon-12 , 1% is Carbon-13 , and carbon-14 occurs in trace amounts, making up as much as 1 Part Per Trillion (0.0000000001%) of the carbon on the Earth. The Half-life of carbon-14 is 5730±40 years. It decays into Nitrogen-14 through Beta-decay .2 The activity of the ''modern radiocarbon standard''3is about 14 disintegrations per minute (dpm) per gram carbon 4. The atoms) in order to trace them along chemical reactions involving the given compound. ORIGIN AND RADIOACTIVE DECAY OF C-14 Carbon-14 is produced in the upper layers of the troposphere and the stratosphere by Thermal Neutron s absorbed by Nitrogen atoms. When Cosmic Ray s enter the atmosphere, they undergo various transformations, including the production of Neutron s. The resulting neutrons (1n) participate in the following reaction: :1n + 14N → 14C + 1H The highest rate of carbon-14 production takes place at altitudes of 9 to 15 Km (30,000 to 50,000 Feet ) and at high Geomagnetic latitudes, but the carbon-14 readily mixes and becomes evenly distributed throughout the atmosphere and reacts with Oxygen to form radioactive Carbon Dioxide . Carbon dioxide also dissolves in water and thus permeates the Ocean s. Carbon-14 can also be produced in Ice by Fast Neutron s causing Spallation reactions in Oxygen . Carbon-14 then goes through radioactive Beta Decay . : By emitting an electron and an Anti-neutrino , carbon-14 decays into stable (non-radioactive) Nitrogen-14 with a Half Life of 5730 years. RADIOCARBON DATING C-14 AND FOSSIL FUELS Most man-made chemicals are made of Fossil Fuel s, such as Petroleum or Coal , in which the carbon-14 has long since decayed. However, oil deposits often contain trace amounts of carbon-14 (varying significantly, but ranging from 1% the ratio found in living organisms to undetectable amounts, comparable to an apparent age of 40,000 years for oils with the highest levels of carbon-14). This may indicate possible contamination by small amounts of bacteria or an unknown second source of carbon-14 production. Presence of carbon-14 in the Isotopic Signature of a sample of carbonaceous material therefore indicates its possible biogenic origin and relatively recent Geologic Age . C-14 AND NUCLEAR TESTS 5 and The above-ground is measured with Accelerator Mass Spectrometry and compared to records of past atmospheric 14C concentrations. Since teeth are formed at a specific age and do not exchange carbon thereafter, this method allows age to be determined to within 1.6 years. This method only works for individuals born after 1943, Radiation in Teeth Can Help Date, ID Bodies, Experts Say , ''National Geographic News'', 22 September 2005Spalding KL, Buchholz BA, Bergman LE, Druid H, Frisen J. Forensics: age written in teeth by nuclear tests. ''Nature''. 2005 Sep 15;437(7057):333-4. PMID 16163340 and it must be known whether the individual was born in the Northern or the Southern Hemisphere . C-14 IN THE HUMAN BODY Since essentially all sources of human food are derived from plants, the carbon that comprises our bodies contains carbon-14 at the same concentration as the atmosphere. The beta-decays from this internal radiocarbon contribute approx 1 mrem/year (.01 (which vary). Carbon-14 can be used as a Radioactive Tracer in medicine. In the Urea Breath Test , a diagnostic test for '' Helicobacter Pylori '', urea labeled with approx 1 μCi (37 KBq ) carbon-14 is fed to a patient. In the event of a ''H. pylori'' infection, the bacterial Urease enzyme breaks down the urea into Ammonia and radioactively-labeled Carbon Dioxide , which can be detected by low-level counting of the patient's breath. 7 SEE ALSO REFERENCES
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