Kinetic studies on oxidation of molecular tritium by soils

Molecular tritium oxidation by soil was investigated in the laboratory. The same oxidation mechanism was found for molecular tritium and hydrogen gas as the addition of hydrogen gas suppressed the oxidation rate of molecular tritium. Analyses by Michaelis-Menten kinetics showed apparent Km values significantly lower at atmospheric hydrogen gas levels (below 2 ppm) than at elevated hydrogen gas levels. Soil temperature affected the oxidation rate as indicated by a change of Vmax values with soil temperature while apparent Km values remained constant. All soils from different locations had an oxidizing ability of molecular tritium and similar apparent Km values. This indicated that oxidation is common in soils and similar enzymes are responsible for the oxidation of molecular tritium at atmospheric hydrogen levels. (author)