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
Induced radioactivity of the nucleus, which releases a neutron. This reaction has a minimum cutoff of 2 MeV (for deuterium) and around 10 MeV for most heavy nuclei. Many radionuclides do not produce gamma rays with energy high enough to induce this reaction. The isotopes used in food irradiation (cobalt-60, caesium-137) both have energy peaks below this cutoff and thus cannot induce radioactivity in the food. Some induced radioactivity is produced by background radiation, which is mostly natural. However, since natural radiation is not very intense in most places on Earth, the amount of induced radioactivity in a single location is usually