The soil radioactivity

The soil radioactivity is due to the occurrence of a high number of radioactive isotopes in the natural environment, which come from different natural as well as artificial sources. They may be categorized into four groups as follows  

The origin of radiation sources leads to either natural or artificial radioactivity. 

The natural radioactivity of soils depends particularly on the origin and composition of the parent rock, on the degree of weathering, and on the prevalent types of the soil formation process (particularly leaching). For example, the soils obtained by weathering of acid rocks contain higher amounts of radioactive elements as compared to those produced from basic rocks. Heavy soils contain higher amounts of radioactive elements than sandy soils. The distribution of radioactive isotopes in the soil profile is usually fairly uniform, and only in certain soils is it possible to observe an increased accumulation in illuvial horizons. 

Natural radioactivity is formed particularly by long-lived isotopes, i.e. by those with half-lives of 10 to 10 years. These isotopes are usually widely scattered in the soil. The activity level depends particularly on contents of uranium, thorium, radium and potassium the radiation energy of these elements represents as much as 98% of the total energy of radiation of all the natural radioactive elements in the soil. 

By the action of the cosmic radiation, nitrogen in the atmosphere is converted to radioactive carbon and tritium H. The radioactive carbon with a half-life of 5770 years and tritium with a half-life of 12.26 years enter the soil with precipitation, and together with radioactive potassium they are included into the biological circulation of elements. The principles of the formation and decay of radioactive carbon are used when determining the age of organic compounds in the organic debris and soils. 

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BIOLOGICAL PROPERTIES dissipation of C14 from soil 571 pg NDPA/M2 was applied to soil, after 2 hrs, only 52.6% was still present approximately 92% of the radioactivity was extractable with methanol, after 8 and 49 days, the soil radioactivity declined to 16.9% and 11% respectively at 8 days, only 16% of the soil radioactivity was extractable with methanol may leach into ground water soil, and aerobic half-lives 21 days-6 months surface water half-life 0.17-1 hr ground water half-life 42 days-12 months anaerobic half-life 84 days-24 months... 

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