During two experimental field releases of tritiated hydrogen, performed in France and Canada, a series of measurements was carried out to trace the pathways of tritium in the environment. Information on plume dispersion, HT deposition and conversion into HTO in contact with soil was obtained from analyses of air and soil samples at different positions within the dispersion sector. It was found that HT dispersion can be properly described by the Gaussian plume model, when in the case of the extremely short release the small dispersion parameters of stable weather conditions are used, although the situation was unstable according to Pasquill's classification. HT deposition velocities evaluated from undisturbed and preconditioned field soils confirmed the laboratory findings that the combined process of deposition and biochemical conversion is correlated to the superposition of two countercurrent functions of the free pore volume: HT diffusion in soil on one hand and microbial action on the other hand.