14C data

Stuiver M, Polach HA (1977) Discussion reporting of 14C data. Radiocarbon 19 355-363... 

Recently, a U.S.S.R.-Czechoslovokian research group have reported 14C data for dated wine samples from the Caucasus Mountains [27]. Their results are in fairly close agreement with our results for the time of overlapping data (figure 5). If the anomalous data for A.D. 1943 are omitted, the fifth order polynomial fit to the data yields a 5 per mil peak to trough amplitude with a phase lag of 4 years behind sunspot numbers. The amplitude... 

Appendix 1. Methods of Radiocarbon (14C) Analysis and Reporting of 14C Data 253... 

APPENDIX L METHODS OF RADIOCARBON (14C) ANALYSIS AND REPORTING OF 14C DATA... 

In this appendix, we briefly describe sample preparation and radiocarbon analysis, as well as the conventions for reporting of 14C data. We have tried to strike a balance between brevity and explanation, addressing common questions we have encountered. Additionally, we urge those interested in using 14C data to read Stuiver and Polach (1977), the paper that established most 14C reporting conventions and from which most of the equations in this appendix were acquired. 

Both AMS and conventional counting facilities report 14C data as the ratio of 14C activity in the sample to that of a known standard. By convention (Broecker and Olson, 1959 Stuiver and Polach, 1977), the standard is corrected to 0.95 times the activity of an oxalic acid standard (0X1), which is normalized to a 813C of -19%o. The sample is also normalized for 13C content as follows The activity of the sample, As, with a 813C of 8 is corrected to a constant 13C abundance (-25%o) by, using the following equation ... 

A common term used for reporting 14C data is fraction Modern (F or F14C Reimer et al., 2004) ... 

Organic/Elemental Carbon, 13C/12C and 14c Data Oak Ridge, TN July, 1983 and March, 1984... 

Mixing lines can also be of negative correlations, as, for example, for salt-poor warm water mixing with a saline cold end member (Fig. 6.19). In such a case the maximum possible temperature of the warm end member can be deduced by extrapolating the best-fit line to zero TDI. A value of 46° C is obtained in the example shown in Fig. 6.19. The temperature of the true warm end member lies between the warmest measured value and the extrapolated value. In the example given in Fig. 6.19, these two values are rather close 39 and 46° C, respectively. Negative correlations in mixed groundwater systems are often obtained with tritium and 14C data plotted versus dissolved ions (old saline water diluted by recent fresh water). The value of tritium and 14C in this respect will be demonstrated in sections 10.6 and 11.10. 

Water with little, but measurable, tritium (0.5-10 TU ) seems to be a mixture of pre-1952 and post-1952 water. The topic of water mixtures is further discussed in section 11.10, along with 14C data. 

The last two hypothetical examples are correct only if the groundwater behaves as a closed system with regard to its 14C 12C ratio. Table 11.2 presents 14C data of basalt aquifers in Hawaii of mainly pre-bomb age, as reflected in the low tritium concentrations. The waters are seen to contain up to 100 mg HC03/1 and have 14C values exceeding 91 pmc in seven out of eight reported pre-bomb cases. It seems, thus, that little or no 14C was lost due to reaction with rocks, and little or no dead carbon (i.e., devoid of 14C) was added by interactions with aquifer rocks, a fact reflected also in the low HCO3 concentration. 

Fig. 11.27 Set of 14C data (pmc) marked on well locations in the Lincolnshire limestone aquifer. The arrow depicts the orginally suggested direction of ground-water flow. Dashed line marks discontinuity between phreatic (A) and confined (B) aquifers. (Data from Dowing et al., 1977.)...

This system has been studied by Geyh and Wirth (1980). Figure 11.28 depicts the outcrop areas and the suggested groundwater flow direction. The 14C data reveal a sharp discontinuity of waters, with 32-70 pmc near the outcrops (A) and 2-7 pmc in the downflow section of the confined aquifer (B)—another example of lack of hydraulic communication between adjacent phreatic and confined systems. 

Mixing of Groundwaters Revealed by Joint Interpretation of Tritium and 14C Data... 

More specifically, we can bracket the pKa values of these sites in the approximate range 19 < pKa 22 because this coal is virtually unreactive toward 9-phenylfluorenyllithium (pKa 18.5). Of particular interest, the 14C data for fluorenyllithium and trityllithium are identical within experimental error. This finding establishes that only a low concentration of acidic C-H sites with 22 < pKa 31 are present in this coal. 

The 14C data probe the number of introduced methyl groups and monitor subtle differences in the coal response toward systematic variations in the reaction conditions however, the data do not identify all of the sites of alkylation. To obtain more definitive structural information on the sites of alkylation, the CP/MAS 13C NMR spectra of the three samples derived from repetitive methylation with fluorenyllithium and [13,14C]H3I were measured. Three difference spectra were obtained 1 minus blank, 2 minus blank, and 3 minus blank, where the numbers refer to the treatment number, and the blank is the sample obtained from reaction of the O-methyl coal with fluorenyllithium followed by a water quench. As before, the nulling of the aromatic carbon envelopes is the subtraction criterion. 

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