The Effect of Anthropogenic CO2 and 14C Sources on the Distribution of 14C in the Atmosphere

Abstract

¹⁴C measurements on continuous weekly samples of atmospheric CO₂ and hydrocarbons, collected in a rather densely populated area are presented. The deviation of the measured ¹⁴C data from the clean air level is primarily due to CO₂ 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 ¹⁴C shift for weekly averages, particularly during the winter season. Natural CO₂ 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 CO₂ 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 ¹⁴CO₂. Atmospheric samples taken in the environment of the pressurized water reactors (PWR) Biblis show that the ¹⁴C release of these reactors is primarily in the form of hydrocarbon ¹⁴C. 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.