Technique, radiocarbon

Radiocarbon technique. Campbell and Sheppard (Campbell et al., 1979) developed a method for OH based on its oxidation of isotopically labeled l4CO that is added to the air sample. Assuming that CO is oxidized to C02 by the reaction with OH, the rate of formation of C02 is given by... 

Extensive intercomparisons using the radiocarbon technique have not been carried out. Campbell et al. (1995) compared measurements using the radiocarbon technique to those from an LIF instrument (Chan et al., 1990). The values obtained were frequently near the detection limits of the instruments, but despite that, were reasonably well correlated (r2 = 0.74). However, the slope of a plot of the radiocarbon versus LIF absolute concentrations was 2.9, i.e., there was a difference of about a factor of three. 

Radiocarbon dating originated with W. F. Libby (1955,1965) and is routinely applied in specialized laboratories of archaeology and in the environmental sciences held. Radiocarbon technique is based on the constant rate at which carbon-14 spontaneously decays. A or ratio can be determined by measuring the... 

In spite of prior difficulties, problems associated with 14C impurities have been overcome, and recently reported ambient HO measurements (84) have given HO concentrations with impressively short collection times of 100 s per HO datum. Current implementation of the radiocarbon technique has been described in detail (85), and repetitive measurements at a clean-air site in eastern Washington state have yielded midday HO concentrations of (5.6 0.1) x 106 molecules per cubic centimeter with impressively high precision (86). Instrumental sensitivity fluctuations were estimated to have an upper bound of 16%, and the detection limit was 105 cm"3 (86). 

In contrast to the primary production, which is estimated by a wide use of radiocarbon techniques, the methods for calculation of the secondary production are based either on the data for the rate of weight growth at different stages of their lifecycle and their abundance, or on the use of physiological characteristics of the organism such as the daily ration, the proportion of the assimilated food in the ration, and the respiration. The data obtained with these methods allow estimation of the values of production of the main species of copepods and other animals [69]. The mean annual values of the... 

Detailed expositions of radiocarbon techniques and applications are found elsewhere (1-8), but for completeness, a brief introduction is given in this chapter. The purpose of this introduction is to summarize the current status of the analytical methods and to show how advances in radiocarbon dating have made it possible to carry out a program for measuring the age of the Shroud of Turin. 

Method C Liquid scintillation counting (LSC) radiocarbon techniques to quantify the biobased content of a product. Method C uses LSC analysis of sample carbon that has been converted to benzene rather than CO2 solutions of Method A. The maximum error is 3%. 

Furthermore, if we assume that the time of calcium carbonate precipitation is the same as that of the buildings constmction, where the lime has been used, it follows that the radiocarbon technique can be used to date old structures such as buildings, bridges and... 

Dating of textiles is possible by means of radiocarbon dating. Developments in this technique have greatly improved its utihty for that purpose, as exemplified by its appHcation in the dating of the Turin Shroud (121). 

Nuclear testing has increased the amount of carbon-14 in the air, and sensitive radiocarbon dating techniques take this increase into account. 

Bischoff JL, Fitzpatrick JA (1991) U-series dating of impure carbonates An isochron technique using total-sample dissolution. Geochim Cosmochim Acta 55 543-554 Broecker WS, Olson EA, Orr PC (1960) Radiocarbon measurements and annual rings in cave formations. Nature 185 93-94... 

Soon after this discovery the harnessing of the technique to the measurement of all the U isotopes and all the Th isotopes with great precision immediately opened up the entire field of uranium and thorium decay chain studies. This area of study was formerly the poaching ground for radioactive measurements alone but now became part of the wonderful world of mass spectrometric measurements. (The same transformation took place for radiocarbon from the various radioactive counting schemes to accelerator mass spectrometry.)... 

An older and long-established technique, radiocarbon decay counting, also known as the "conventional" method of radiocarbon dating, is based on detecting and counting the amount of beta radiation emitted in unit time by radiocarbon atoms in a sample of known weight. 

A more recently developed technique, known as the accelerator mass spectrometry (AMS) radiocarbon dating technique, based on counting, in a mass spectrometer, the relative amount of radiocarbon to stable carbon isotopes in a sample (see Textbox 10). 

The conventional radiocarbon decay counting technique generally provides reliable results, but it has some limitations the following are worth mentioning ... 

Practical considerations limit the use of the radiocarbon dating technique to a range of 200-50,000 years samples less than 200 years old cannot be called... 

Uranium Series Dating. Reliable dating of bone is possible when using the technique known as uranium series dating (see Textbox 16). The technique, which is also based on measuring relative amounts of uranium, makes possible dating very old bones, beyond the range that can be dated with radiocarbon, that is, over 40,000 years and up to 500,000 years old (Schwarcz 1997 Ivanovich and Harmon 1992). 

Many more studies have been initiated in attempts to explain the discrepancy between the belief of millions of people and the evidence provided by the radiocarbon dating technique on the age of the shrouds s cloth. Such studies, however, have resulted only in still further studies and a persistent controversy on the real nature of the relic. 

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