Determination of potassium in environmental samples using detection of ⁴⁰K

Potassium is a radioactive biogenous element. Its amount in earth crust represents approximately 2.1 weight %, which refers to the ninth highest concentration of elements in the lithosphere. The presence of the mentioned alkali metal in the environment, considering its chemical and physical properties, belongs to the basic requirements for life in Earth. In addition to 25 isotopes, another 4 nuclear isomers of potassium are known. Because of its long half-life (1.248.10⁹ years), ⁴⁰K is one of most abundant radionuclides in nature, even though its concentration in potassium is very low (0.0119 %). The presence of ⁴⁰K in potassium enables the determination of this element by measuring of its radioactivity. The work encompasses the determination of potassium in synthetic fertilizers and in the soil samples by scintillation γ-spectrometry using the detection assembly consisting of the well type detector 76BP76/3 NaI(Tl) made by Envinet (Czech Republic) operated by the data evaluation program ScintiVision-32 (product of Ortec, USA) and of the lead shielding made by Envinet (Czech Republic). The work involves information concerning the estimation of detection efficiency, estimation of ⁴⁰K γ-photons-self-absorption in the samples as well as estimation of the necessitated measurement time for required relative standard deviation. (authors)