Chlorine-36 is an isotope of chlorine. Chlorine has two stable isotopes and one radioactiveenvironmental isotope: the cosmogenic isotope <sup>36</sup>Cl. The ratio of <sup>36</sup>Cl to stable <sup>37</sup>Cl in the environment is ~700 × 10<sup>−15</sup>. Its half-life is 301,000 ± 4,000 years. The long half-life of <sup>36</sup>Cl makes it useful to date groundwater up to one million years old.Cl values of hydrologic systems are related to diffusion processes.
Chlorine-36 is produced in the upper atmosphere through spallation reactions and in solid materials on the surface of the earth in three ways: spallation reactions, muon reactions and thermal neutronabsorption. Spallation reactions also occur when gamma rays interact with minerals in the top several meters of the Earth's surface. It can also be produced through muon reactions and thermal neutron absorption. <sup>36</sup>Cl was also produced during nuclear bomb testing in the middle of the 20th century.
Trace amounts of radioactive <sup>36</sup>Cl exist in the environment, in a ratio of about 7 × 10<sup>−13</sup> to 1 with stable isotopes. <sup>36</sup>Cl is produced in the atmosphere by spallation of... Read More