Chlorine-36

Chlorine-36

Chlorine-36 (36Cl) is an isotope of chlorine that is of interest both for its radioactive properties and its use in environmental and geological studies. Chlorine-36 is a cosmogenic nuclide, produced in the atmosphere through interactions between cosmic rays and argon atoms. It has a half-life of approximately 301,000 years, making it useful for dating ice, groundwater, and sediments in the age range of 60,000 to 1 million years.

Production

Chlorine-36 is produced in the atmosphere through spallation of argon by cosmic rays. It can also be produced in situ in the Earth's crust through the capture of thermal neutrons by 35Cl (a natural chlorine isotope), which can occur in the subsurface as a result of the natural radioactive decay of uranium and thorium.

Decay

36Cl decays by beta decay to 36Ar with a half-life of about 301,000 years. The long half-life of 36Cl makes it suitable for geochronology and hydrology studies, particularly in the dating of old groundwater and polar ice.

Applications

Hydrology

In hydrology, 36Cl is used to date the time of water recharge and to trace the source and movement of groundwater. Its long half-life allows for the dating of waters up to a million years old, which is particularly useful in arid regions where groundwater recharge rates are slow.

Geology

In geology, chlorine-36 has been used to date exposure ages of rocks and sediments. This application is valuable in the study of glacial and fluvial sediments, as well as in the assessment of erosion rates and the development of soil profiles.

Environmental Science

Chlorine-36 has also found applications in environmental science, particularly in the study of the long-term confinement of radioactive waste. Its behavior in the environment helps to understand the migration of radioactive contaminants in the geosphere.

Safety and Handling

As a radioactive isotope, proper safety protocols must be followed when handling chlorine-36. This includes the use of appropriate shielding, handling tools, and monitoring devices to protect against radiation exposure.

See Also

• Isotopes of chlorine
• Cosmogenic nuclide
• Geochronology
• Hydrology