Radiocarbon concentrations, natural

In 1946, the problem was demonstrating that the most fundamental assumptions did in fact hold. Initially, this meant obtaining measurements of the natural radiocarbon concentrations in living organics to see if it occurred in the amount expected and if the worldwide distribution of radiocarbon was essentially constant. An experiment was devised whereby biological methane gas derived from the sewage disposal plant at Baltimore, MD and petroleum methane from the Sun Oil Co. refinery were each enriched by a similar factor in a thermal diffusion column. It was assumed that the petroleum methane contained no because of its age in excess of many tens of millions of years whereas the biological methane contained about 17-18 dpm radiocarbon per g of carbon. The experiment was conducted, and the results confirmed the calculations (26). 

Measurement of Natural Radiocarbon Concentrations. By the middle of the 1950s, the original solid carbon method of assay of natural radiocarbon concentrations had been completely superseded by the development of either gas or liquid scintillation counting systems. More than 20 years of experimentation and development in the low level counting technology field has turned what was once a black art and analytical tour de... 

Methodology of Radiocarbon Dating. The natural concentration of radiocarbon in materials on earth is extremely low add to this the fact that the beta radiation emitted by radiocarbon is very weak, and the conclusion is that the measurement of natural levels of radiocarbon is a rather difficult task. Indeed, very elaborate physical and chemical procedures are required to obtain accurate radiocarbon measurements and dates. 

Because of the ease of making such measurements, many descriptions of the technique have tended to emphasize its impact as a new 14C dating method. We believe that this emphasis on radiocarbon dating has been somewhat premature, as there is an enormous practical difference between the detection of 14C atoms in samples at natural concentrations using existing equipment and the measurement of 12C/13C/14C isotopic ratios with the necessary precision for dating to better than one percent accuracy. In this... 

The chemistry of carbon, and radiocarbon, in the atmosphere represents one of the most important areas of environmental research today. The primary practical reason for this is the increasing attention which must be paid to the critical balance between energy and the environment, especially from the viewpoint of man s perturbations of natural processes and his need to maintain control. Probably more than other species, carbonaceous molecules play a central role in this balance. Some of the deleterious effects of carbonaceous gases and particles in the atmosphere are set down in Table 3. The potential effects of increased local or global concentrations of these species on health and climate have led to renewed interest in the carbon cycle and the "C02 Problem". It should be evident from the table, however, that carbon dioxide is not the only problem. In fact, the so-called "trace gases and particles" in the atmosphere present an important challenge to our interpretation of the climatic effects of carbon dioxide, itself [20]. 

The concentration of RDOM is simply equal to the measured concentration of DOM in deep waters (>1000 m), where its apparent radiocarbon age of 4000-6000 years is substantially greater than the timescale of thermohaline circulation in the earth s oceans (Druffel et al., 1992). Bioassay experiments have been used to verify the refractory nature of DOM in the deep sea (Barber, 1968). 

Figure 5 Simulated radiocarbon and carbon cycle results from a three-dimensional global ocean biogeochemical model. Depth-latitude sections are shown for (a) DIG concentration (pmoll" ) and (b) natural preindustrial) radiocarbon (A C, per mil) along the prime meridian in the Atlantic Ocean.

Kunioka, M., Ninomiya, R, Funabashi, M., Novel evaluation method of biodegradabilities for oil-based polycaprolactone by naturally occurring radiocarbon-14 concentration using accelerator mass spectrometiy based on iso 14855-2 in controlled compost Polymer Degradation and Stahilitv. 7, 1279-1288 (2007), DOl http //dx.doi. org/10.1016/j.potymdegradstab.2007.03.028. 

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