Environmental radioactivity g) to that of the soil water (Bq ml). If the radioactivity is tightly bonded to by the minerals in the soil then less radioactivity can be absorbed by crops and grass growing in the soil. One dramatic source of man-made radioactivity is a nuclear weapons test. The glassy trinitite formed by the first atom bomb contains radioisotopes formed by neutron activation and nuclear fission. In addition some natural radioisotopes are present. A recent paper reports the levels of long-lived radioisotopes in the trinitite. The trinitite was formed from feldspar and quartz which were melted by the heat. Two samples
Environmental radioactivity of the event. These can be dated by a SHRIMP ion microprobe. One of the advantages of this method is that any sample provides two clocks, one based on uranium-235's decay to lead-207 with a half-life of about 703 million years, and one based on uranium-238's decay to lead-206 with a half-life of about 4.5 billion years, providing a built-in crosscheck that allows accurate determination of the age of the sample even if some of the lead has been lost. Environmental radioactivity Environmental radioactivity is produced by radioactive materials in the human environment. While some radioisotopes, such as strontium-90 (Sr)