Carbon dating becomes more accurate
Scientists from the Australian Nuclear Science and Technology Organisation (ANSTO) and Thailand’s Naresuan University have helped to make carbon dating a more accurate chronological tool. The work was conducted by Quan Hua, Mike Barbetti, Vlad Levchenko and Andrew Smith.
The scientists explained that the use of bomb-pulse radiocarbon has become widespread as a precise dating tool for the last 60 years. Carbon-14 (14C) was generated by nuclear explosions in the atmosphere due to weapons testing in the ‘50s and ‘60s, and the resultant 14CO2, gradually distributed throughout Earth’s atmosphere, “essentially put a mark in time”.
The atmospheric 14CO2 level is now approaching its natural pre-bomb value. In the troposphere - the region of Earth’s atmosphere below 10,000 metres - the level of bomb-derived 14CO2 was extremely variable in space and time. For this reason, in order to radiocarbon-date materials formed during the last 60 years, scientists need to know what those atmospheric levels were.
The researchers studied tree rings for this purpose, as the trees had photosynthesised the 14CO2 into cellulose in their annual rings. The scientists measured the level of radiocarbon in tree rings from Thailand, Indonesia and Australia using ANSTO’s particle accelerators.
The results, together with published radiocarbon data from tree rings and atmospheric carbon dioxide samples from around the world, revealed that the level of atmospheric 14CO2 during the early bomb period from the 1950s to the 1960s was strongly influenced by worldwide atmospheric circulation patterns.
“Using this compilation, we have been able to reconstruct regional and temporal records of atmospheric 14CO2 levels to make carbon dating a more accurate chronological tool,” the researchers said.
“In addition, five zonal 14C data sets have been reconstructed to be used as ‘radiocarbon calibration curves’ for improved bomb-pulse 14C dating.”
ANSTO last week welcomed a $654 million federal Budget allocation over four years. This includes $76.6 million for the country’s only nuclear research reactor, OPAL, and $22.6 million to develop detailed design options for a national radioactive waste management facility.
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