From Atoms to Aquifers

Atom Trap Trace Analysis (ATTA) was recently used to help researchers determine, for the first time, the age and direction of water movement in the largest underground aquifer in the Middle East.

Researchers from Argonne; the University of Illinois at Chicago (UIC); the University of Bern, Switzerland; and the Egyptian Geological Survey and Mining Authority gathered samples of a rare gas, krypton-81, from the Nubian aquifer, a huge reservoir of fresh water below the Sahara Desert. Miniscule amounts of krypton-81 are produced naturally in the atmosphere by cosmic rays, and the level of the gas in aboveground water is relatively constant. As water sinks to aquifer levels, it no longer absorbs fresh air, and the krypton-81 slowly decays. Comparing the amount of krypton-81 in the ancient samples to current levels reveals the samples' ages.

The Nubian aquifer samples ranged in age from 200,000 to 1,000,000 years. This suggests a flow pattern north and east, toward the Mediterranean Sea, at about one meter (three feet) per year, “about the same rate as grass grows,” said UIC's Neil Sturchio.

Argonne's Zheng-Tian Lu sees potential applications in several other fields. Argon-39, for example, can be used to trace deep ocean currents. Another potential application is use of calcium-41 as a medical tracer to monitor bone loss from osteoporosis. With the powerful detection abilities of ATTA, a subject could ingest just a small, non-harmful amount of the isotope, which would be taken up into the bones. ATTA could be used to detect the miniscule amounts of calcium-41, and by implication regular calcium, leaving the body over a period of years. This method would give researchers a powerful new way to test treatments for preventing osteoporosis. ATTA may also find use as an extremely sensitive leak sensor and environmental monitor at U.S. Department of Energy “legacy waste” cleanup projects.

Lu is already making plans for ATTA III, which may improve efficiency 100 times over the current model.