Environmental tracers age dating young groundwater
As a consequence, atmospheric CFC concentrations have begun to decrease.
Atmospheric concentrations of CFCs are not expected to decrease quickly, so CFC dating will continue to work for most young groundwater for many years to come.
Hydrologists know the rate of decay of carbon-14, so by measuring differences in groundwater carbon-14 in an aquifer, they can calculate groundwater ages.
Because the half-life of carbon-14 is long (5,730 years), this method is useful for determining the age of groundwater between about 1,000 and 30,000 years old.
Hydrologists employ a variety of techniques to measure groundwater age.
For relatively young groundwater, chlorofluorocarbons (CFCs) often are used.
Given that groundwater can be quite old, it becomes apparent that activities that cause groundwater pollution today can result in long-term resource problems—problems that have the potential to last for millennia.
Description: Various environmental isotopes and tracers are used to determine the age of groundwater.
For very old groundwater, carbon-14 dating often is used.
By measuring the CFC concentration in groundwater, hydrologists know how long ago the water entered the aquifer.
In the United States and other developed countries, CFCs are being phased out of use because they contribute to atmospheric ozone depletion.
Once water enters an aquifer, it becomes isolated from the atmosphere, and it carries a CFC signature (a distinctive chemical composition) as it travels through the aquifer.
This signature reflects the atmospheric concentration when the water was at the surface.
Search for environmental tracers age dating young groundwater:
Hydrologists account for this dilution before calculating carbon-14 groundwater ages.