Studies of HT Deposition to Unsaturated Soil

This paper presents further results of studies of tritium oxidation in unsaturated soil by microorganisms. The objective of the study was to develop a laboratory technique to study the kinetics of HT deposition to soil due to its oxidation and the kinetics of HTO retention in local soils, which are used for agriculture and forestry. Kinetics of HT to HTO oxidation and deposition to soil has been studied in laboratory conditions. An experimental cell was developed to prepare a mixture of air, water vapor and tritium gas and to pump the mixture through the soil sample under study. The activity of HTO converted in the soil sample during a certain period of time was used to determine the oxidation rate. This rate varies, depending on the catalytic and/or biological activity of the soil material. Theoretical considerations have shown that the deposition rate can be expressed by the effective rate of oxidation, which formally corresponds to the first-order HT oxidation. The rate of HT to HTO conversion and deposition to soil is required for assessment of consequences of HT release into the atmosphere.