借助氚/氦-3技术管理水资源预算

The tritium/helium-3 technique has become an increasingly important technique over the last decade because previous methods using just tritium are becoming less useful.

“Tritium can tell us the age of groundwater and whether it’s being recharged, which is very important information, but tritium alone cannot give us the level of detail we need. Decision makers need to know more: what does it mean that the water is young? How young is young?” Marah said.

Due to atmospheric tests of thermonuclear devices in the 1950s, levels of tritium in the atmosphere sharply increased in the 1960s and have since gradually declined.

“From the 1960s to 1990s, tritium was a good tracer, but today there is less tritium in the atmosphere because it has been decaying into helium-3, so we now focus more on the ratio of tritium to helium-3, which is much more precise,” Marah said. 

Helium is a noble gas, which means it is stable and does not have chemical reactions with other elements found in rocks or water. This makes it a consistent and reliable reference point. By knowing the concentration of helium that comes from tritium — helium-3 — compared to the total helium in the water, as well as the concentration of other noble gases, scientists can determine the exact age of young water. 

“The use of noble gases for water studies is growing because now analytical devices have improved enough to detect the very small amounts these gases come in,” said Takuya Matsumoto, an isotope analyst at the IAEA. “For many countries, though, it is not economical or feasible to set up their own labs to do these analyses. The IAEA Isotope Hydrology Laboratory makes this service available to countries so they can benefit from this sophisticated technique.” 

The IAEA Isotope Hydrology Laboratory is one of just a handful of laboratories in the world capable of performing these analyses. Beginning in 2010, a team of IAEA and external experts from ten countries spent six years setting up, calibrating and testing the IAEA’s mass spectrometer machine, as well as the mathematical model for analysing results. They also developed guidelines for using the tritium/helium-3 technique. The lab has since been working around the clock processing between 300 to 400 samples each year from countries worldwide.