Trace radiocarbon analysis of environmental-samples

Abstract

In the atmosphere, radioactive `4C is produced at a roughly constant rate and decays with a half-life of 5730 y. Human activity perturbs the natural, steady-state level of 14C. Combustion of fossil fuels and emission of pollutants derived from fossil feedstocks dilute 4C with dead 2C (the Suess effect), and nuclear weapons tests produce excess 4C (the effect). Therefore, sources are often revealed by measurement of C in species of environmental concern, such as greenhouse gases (CO2, CO, CH4), atmospheric particles, and toxic or carcinogenic organic compounds. Atmospheric weapons testing peaked in the early 1960s, and, in 1963, the atmospheric radiocarbon level was about twice the natural level [1]. Since then, the 14C concentration has been declining, largely because of equilibration of atmospheric CO2 with carbonate in the world's oceans. The changing distribution of bomb carbon in the ocean has been measured to investigate ocean circulation patterns [2,3,4]. As nuclear power plants become more widely used, they, too, may become important sources of atmospheric 14C. Radiocarbon has already been exploited as an inherent tracer to investigate the dispersion of plumes from nuclear power plants [5,6,7].