The radiocarbon sample archive of trondheim

Atmospheric CO2 samples have been collected by the Trondheim Radiocarbon Laboratory since the 1960s. The remaining material from the measurements has been precipitated as CaCO3 and stored in glass containers. We investigated some of the stored samples to assess whether the material could still be used for remeasurements of atmospheric radiocarbon (C-14) content, or if it has been contaminated during the years of storage. We attempted different methods to clean the carbonate and release the CO2 for new measurements. The results indicate that the older samples before 1970 show a significant change in C-14 content compared to the original measurements, and that our cleaning methods have only little effect. Later samples from the 1970s, which were archived in glass containers with a different lid, show a lower contamination that, however, still leads to an added uncertainty of several pMC and makes these samples unreliable.