δ¹⁴CO₂ Record from Vermunt

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Investigators

I. Levin, B. Kromer, H. Schoch-Fischer, M. Bruns, M. Münnich, D. Berdau, J.C. Vogel, and K.O. Münnich
Institut für Umweltphysik,
University of Heidelberg, D-69120,
Heidelberg, Germany

Period of Record

February 1959 - June 1983

Methods

The sampling at Vermunt was discontinued in 1983. During sampling from 1959 to 1983, the sampling methods were modified twice (Levin et al. 1985). From 1959 through November 1965, three dishes with 1.5 L of 0.5 normal sodium hydroxide (NaOH) carbonate-free solution were exposed to the atmosphere for ~3 days, and the atmospheric CO₂ absorbed during that time was recovered by acid evolution. From November 1965 through May 1975, samples were collected by pumping fresh air continuously for 10 days through a box containing 1.5 L of a 0.5 normal NaOH solution. The method has been described by Münnich and Vogel (1959). From May 1975 to the time sampling stopped, a technique described by Levin et al. (1980) was used. Air was pumped through a rotating glass tube filled with a packed bed of Raschig rings (hard glass) to enlarge the surface of the absorbing NaOH solution (200 ml of 4 normal NaOH). The CO₂ absorption was quantitative and samples represent mean values of 10 days to 2 weeks. In the laboratory, the samples were extracted from the NaOH solution in a vacuum system by adding hydrochloric or sulfuric acid. The CO₂ gas samples were purified over charcoal and counted in a proportional counter (Schoch et al. 1980). Delta ¹⁴C values are given relative to the NIST oxalic acid activity corrected for decay (Stuiver and Polach 1970).

More details on the sampling methods and laboratory procedures are provided in Levin et al. (1985), Münnich (1957), Schoch et al. (1980), and Levin et al. (1980).

Vermunt, Austria
Remote electric power station situated at the upper water reservoir of the Ill-Werke
47° N, 10° E
1800 m above MSL

Trends

The long-term δ¹⁴CO₂ record from Vermunt exhibits the same δ¹⁴CO₂ decline seen at other sampling locations around the world. According to Levin et al. (1985), the Vermunt record is representative of the higher altitude ¹⁴CO₂ level over Central Europe. Levin et al. (1985) reported marked seasonal variations in the ¹⁴CO₂ levels at Vermunt in the early 1960s, up to ca δ¹⁴CO₂ = 200 per mil, resulting mainly from springtime injections of bomb ¹⁴ CO₂ from the stratosphere. Levin et al. (1985) reported that the peak-to-peak variations in δ¹⁴CO₂ since 1976 at Vermunt were ~ 20 per mil, due partly to seasonal variations of the contribution of fossil fuel CO ₂.

References

• Hut, G. 1987. Stable isotope reference samples for geochemical and hydrological investigations. In Report to the Director General, IAEA, Vienna.
• Levin, I., K.O. Münnich, and W. Weiss. 1980. The effect of anthropogenic CO₂ and ¹⁴C sources on the distribution of ¹⁴C in the atmosphere. In Proceedings of the 10th International Radiocarbon Conference (M. Stuiver and R. Kra, eds.) Radiocarbon 22(2):379-91.
• Levin, I., B. Kromer, H. Schoch-Fischer, M. Bruns, M. Münnich, D. Berdau, J.C. Vogel, and K.O. Münnich. 1985. 25 years of tropospheric ¹⁴C observations in central Europe. Radiocarbon 27(1):1-19.
• Münnich, K.O. 1957. Messung natürlichen Radiokohlenstoffs mit einem CO₂-Proportionalzühlrohr. Ph.D. thesis, Universität Heidelberg, Heidelberg, West Germany.
• Schoch, H.M., Bruns, K.O. Münnich and M. Münnich. 1980. A multicounter system for high precision C-14 measurements. In Proceedings of the 10th International Radiocarbon Conference (M. Stuiver and R. Kra, eds.) Radiocarbon 22(2):442-47.
• Stuiver, M., and H.A. Polach. 1977. Discussion: Reporting of ¹⁴C data. Radiocarbon 19(3):355-63.

12/5/97