The Effect of Anthropogenic CO 2 and 14 C Sources on the Distribution of 14 C in the Atmosphere

Abstract

14 C measurements on continuous weekly samples of atmospheric CO 2 and hydrocarbons, collected in a rather densely populated area are presented. The deviation of the measured 14 C data from the clean air level is primarily due to CO 2 from the combustion of fossil fuels. This is confirmed by fossil fuel admixture estimates individually calculated with an atmospheric dispersion model. Up to 10 percent admixture is predicted by this model and observed from the 14 C shift for weekly averages, particularly during the winter season. Natural CO 2 admixture due to soil respiration, however, even in winter, is of the same order of magnitude, but much larger in the warm season: the considerable variations in CO 2 concentration in summer are almost exclusively controlled by natural sources. Using tree leaf samples, we have been able to identify boiling water reactors (BWR) as weak sources of 14 CO 2 . Atmospheric samples taken in the environment of the pressurized water reactors (PWR) Biblis show that the 14 C release of these reactors is primarily in the form of hydrocarbon 14 C. The source strength of the various power plants, calculated on the basis of our observations in their environment, ranges from 0.5 to 7Ci per year.