Deposition of tritiated water vapour to water surface in an outdoor field

Deposition of tritiated water vapour in the atmosphere to a water surface was studied in an outdoor field, where elevated concentrations of tritiated water vapour existed in the atmosphere over twelve days. Exchange velocities of tritiated water vapour between air and water were evaluated from tritium concentrations in air and water obtained in the field experiment. It was found that the average of outdoor exchange velocities was about three times greater than that observed in a nuclear reactor room previously. Relationships between the outdoor exchange velocities and meteorological conditions were analysed to derive a multiple correlation equation. The wind speed was strongly correlated with the exchange velocity and the air temperature appeared to have an enhancing effect on the velocity. These observations were supported by a follow-up experiment conducted on a laboratory scale.