HEIDELBERG RADIOCARBON LAB – ESTABLISHING A NEW CARBON DIOXIDE EXTRACTION LINE FOR CARBONATE SAMPLES

• Published in: Radiocarbon 2021-06, Vol.63 (3), p.915-924
• Main Authors: Therre, S, Proß, L, Friedrich, R, Trüssel, M, Frank, N
• Format: Article
• Language: English
• Subjects: Archives & records; Calibration; Carbon dioxide; Efficiency; Hydrochloric acid; Nitrogen; Paleoclimatology; Radiometric dating; Reproducibility; Sensors
• ISSN: 0033-8222; 1945-5755
• DOI: 10.1017/RDC.2021.28

To achieve high-precision and reproducible results from radiocarbon (14C) dating of carbonate samples in paleoclimate research, a new CO2 extraction line was designed, constructed, and characterized at the Heidelberg Radiocarbon Lab of the Institute of Environmental Physics, Heidelberg. The setup includes a circular glass-tube design, which is operated at vacuum pressure levels of the order of 10–5 mbar. The efficiency of the extraction process was assessed, showing significantly favorable conditions for solid piece samples (99.58 ± 4.69)% over powdered samples (88.28 ± 10.03)%. Process blank values are below 0.2 pMC apparent 14C activity. Repeated measurements of IAEA C2 standards with an average value of (41.09 ± 0.23) pMC attest high accuracy and reproducibility of the instrument. Six consecutive samples of 6 to 12 mg carbonate mass can be processed in one run of roughly 2.5 hours. Thus, the new setup contributes to time-efficient and reproducible radiocarbon dating results for paleoclimate research at the Institute of Environmental Physics. In a first application, Dead Carbon Fraction (DCF) values of a Holocene alpine stalagmite from Schratten Cave are presented, revealing extraordinarily high offsets between atmospheric and stalagmite 14C with DCF values between (49.4 ± 0.4)% and (61.6 ± 0.4)%.