A method has been developed to determine the deposition velocity of elementary tritium (in the form of a hydrogen-tritium molecule, HT) into soil. Soil samples were collected and refrigerated. The decrease of the HT is the head space above the soil core is continuously recorded by an ionization chamber. The triticated water, HTO, which has been formed and released into the gas space is removed by cooling traps. It has not been conclusively proved that organisms are responsible for the oxidation of HT, but sterilized soil and soil heated to 50 C do not convert HT to HTO.
The deposition velocity depended on soil type and particle size. Artificial compression did not significantly alter the deposition velocity. Soil water content was, however, closely correlated with deposition velocity. For arable and pasture soil, deposition velocity showed an annual cycle. Forest soil had the highest deposition velocity.
The method was confirmed by 2 field release experiments. The oxidation product HTO was diluted in the local water cycle. The most serious impact resulted from the reemission of HTO from the soil, which depended on wind velocity. HTO was taken up inter plant leaves from the soil by the transpiration stream and from air water vapour by an isotopic exchange.
CONVERSION OF ELEMENTARY TRITIUM (HT) IN AGRICULTURALLY USED SOILS, OXIDATION OF HT TO HTO AND SYNTHESIS TO ORGANICALLY BOUND TRITIUM.