Radiocarbon isotope dilution

Fossil fuel emissions alter the isotopic composition of atmospheric carbon, since they contain no C and are depleted in C. Releasing radiocarbon-free CO2 to the atmosphere dilutes the atmospheric C content, 3delding lower C/C ratios ("the Suess effect"). From 1850 to 1954 the C/C ratio in the atmosphere decreased by 2.0 to 2.5% (Fig. 11-23) (Suess, 1965 Stuiver and Quay, 1981). Then, this downward trend in C was disrupted by a series of atmospheric nuclear tests. Many large fission explosions set off by the United States with high emission of neutrons took place in 1958 in the atmosphere and the Soviet Union held extensive tests during... 

From both types of isotope analyses, we must conclude that there is no evidence for the large regional water flow that had been assumed until these analyses were performed and discussed. We must now accept that the radiocarbon age of the water in those wells whose analyses have been discussed in this communication can only be explained by the existence of local flow. Other factors possibly affecting the radiocarbon ages are being investigated in this aquifer, such as, e.g., carbon precipitation or dilution (Oeschger, 1974) and subsurface radiocarbon production (Zito et al., 1980). 

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