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 (¹⁴C) 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 ¹⁴C 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. [ABSTRACT FROM AUTHOR]