Environmental radioactivity is produced by radioactive materials in the human environment. g. Tritium, result from natural processes and human activities. The concentration and location of natural isotopes, particularly uranium-238. Radioactivity is present everywhere, and has been since the formation of the earth, according to the IAEA, soil typically contains the following four natural radioisotopes, 40K, 226Ra, 238U, and 232Th. In one kilogram of soil, the amounts to an average 370 Bq of radiation, with a typical range of 100–700 Bq. Some soils may vary greatly from these norms, a recent report on the Sava river in Serbia suggests that many of the river silts contain about 100 Bq kg−1 of natural radioisotopes. According to the United Nations the normal concentration of uranium in soil ranges between 300 μg kg−1 and 11.7 mg kg−1, synthetic radioisotopes also can be detected in silt. Some relationship between distance and activity can be seen in their data, when fitted to an exponential curve, normal licensed releases which occur during the regular operation of a plant or process handling man-made radioactive materials. For instance the release of 99Tc from a nuclear medicine department of a hospital which occurs when a given a Tc imaging agent expels the agent. Releases of man-made radioactive materials which occur during an industrial or research accident, releases which occur as a result of military activity. For example, a weapons test. Releases which occur as a result of a crime, for example, the Goiânia accident where thieves, unaware of its radioactive content, stole some medical equipment and as a result a number of people were exposed to radiation. Releases of naturally occurring radioactive materials as a result of mining etc, for example, the release of the trace quantities of uranium and thorium in coal, when it is burned in power stations. Just because a radioisotope lands on the surface of the soil, after release into the environment, radioactive materials can reach humans in a range of different routes, and the chemistry of the element usually dictates the most likely route. Using milk as an example, if the cow has an intake of 1000 Bq of the preceding isotopes then the milk will have the following activities. 90Sr,2 Bq dm−3 137Cs,5 Bq dm−3 239Pu,0.001 Bq dm−3 241Am,0, the distribution coefficient Kd is the ratio of the soils radioactivity to that of the soil water. If the radioactivity is tightly bonded to by the minerals in the then less radioactivity can be absorbed by crops. Cs-137 Kd =1000 Pu-239 Kd =10000 to 100000 Sr-90 Kd =80 to 150 I-131 Kd =0.007 to 50 One dramatic source of radioactivity is a nuclear weapons test
The contributions made by the different isotopes to the dose (in air) caused in the contaminated area in the time shortly after the accident. This image was drawn using data from the OECD report, the Korean table of the isotopes and the second edition of 'The radiochemical manual'.
Levels of radioactivity in the Trinity glass from two different samples as measured by gamma spectroscopy on lumps of the glass
Fallout around the Trinity site. The radioactive cloud moved towards northeast with high röntgen levels within about 100 miles (160 km).