Abstract |
The noble gas radio isotopes 81-Kr (t 1/2 = 229 ka), 85-Kr (t 1/2 = 12 a) and 39-Ar
(t 1/2 = 268 a) are valuable dating tools for groundwater, ocean water and glacier
ice , serving applications such as drinking water management ocean current tracing
and climate reconstruction. Together with 14-C, these radioisotopes cover an age
range from present back to 1.3 million years. Due to their extremely low
environmental abundances (10-17 ... 10-11) corresponding to only a few thousand
atoms per kilogram of water or ice , their detection is very challenging and in the
case of 81-Kr, has practically not been possible in the past. In the recent two
decades, the laser based method Atom Trap Trace Analysis (ATTA), which detects
single atoms via their fluorescence in a magneto optical trap, has succeeded in
measuring these radio isotopes on natural levels. Initially, tons of water or ice
were necessary for ATTA , which severely hampered its use for dating of
environmental samples. Due to progress in the ATTA instruments, the sample size
could be lowered to 10 kg of water or ice, allowing for applications such as dating
of deep water from the Pacific Ocean and ice cores from Antarctica and Tibet. Here,
we will present an overview of the ATTA method, recent dating results on
groundwater, ocean water and glacier ice as well as our latest advances towards
81-Kr and 39-Ar dating with 1 kg of water or ice.
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