Natural Radiocarbon from Cosmic Radiation

Abstract

C 14 produced by the N u (n, p) reaction of cosmic-ray neutrons has been detected and identified. The C 14 concentration of biological methane was enriched by factors of up to 260-fold by thermal diffusion to raise the activity to convenient levels for counting. The pure methane was used as the filling gas in large Geiger-Mtiller counters.The activity in biological methane was found to be 10.5 disintegrations per minute per gram C, or 0.95 X10~1 2 gram C 14 per gram C. This is in reasonable agreement with the value predicted from the estimated values of the cosmic-ray neutron flux and the amount of carbon in exchange equilibrium with the atmosphere. No significant activity was detected in petroleum methane.A discussion of the thermal diffusion enrichment factor is given.

Simulating the integrated summertime Δ<sup>14</sup>CO<sub>2</sub> signature from anthropogenic emissions over Western Europe

“…This typically applies only to carbon in fossil reservoirs, as other carbon reservoirs are continuously supplied with fresh 14 C from exchange with the atmosphere where 14 CO 2 is produced in the stratosphere and upper troposphere (Libby, 1946;Anderson et al, 1947). In the natural carbon balance this 14 C would cycle through the atmospheric, biospheric, and oceanic reservoir until it decays.…”

“…For example, interpretation of 14 C in air samples from aircraft requires detailed dispersion modeling of surface emissions into a highly dynamic atmosphere, while interpretation of monthly integrated air samples from tall towers requires the inclusion of the re-emergence of old 14 C signals after longer turn-over in the oceans and biosphere. In a recent publication (Bozhinova et al, 2013), we showed that the interpretation of growing season integrated plant samples additionally requires simulation of location and weather dependent photosynthetic uptake and plant development patterns. A successful 14 C monitoring strategy will thus depend D. Bozhinova et al: Modeling 14 CO 2 for Western Europe 7275 strongly on our ability to capture these diverse processes on diverse scales.…”

In-Situ Cosmogenic 14C: Production and Examples of its Unique Applications in Studies of Terrestrial and Extraterrestrial Processes

“…Radiocarbon ( 14 C) is produced in the earth's atmosphere by the capture of slow cosmic ray neutrons by the atmospheric 14 N nuclei. This was the first cosmic-ray-produced isotope to be discovered in 1947, in an experiment using sewage methane (Anderson et al 1947). Soon thereafter, it was applied to archaeological/anthropological dating (Libby et al 1949;Libby 1952).…”

Inductively coupled plasma- and glow discharge plasma-sector field mass spectrometry : Part I. Tutorial: Fundamentals and instrumentation

“…When one or more isotopes of an element are daughter nuclides of a radioactive decay, the isotope ratio(s) of the element depend on the original concentration of the mother nuclide in the sample and the time. The natural radioactivity is, e.g., used for dating via the half-life in archaeometry (e.g., radiocarbon dating) [104][105][106] and geochronology (e.g., U-Pb dating) [107][108][109] or for using the isotopic variation as natural fingerprint (e.g., Sr, Pb). [110][111][112][113] The second effect derives from simple mass-dependent thermodynamic processes (e.g., evaporation), simply influenced by preferential diffusion of lighter isotopes.…”