DEPOSITION OF HEAVY-WATER ON SOIL AND REEMISSION TO THE ATMOSPHERE

Field experiments using heavy water as a tracer instead of tritiated w ater (HTO) were carried out in November 1995 and August 1996 in Japan. The objective of these experiments was to estimate the behavior of HT O in the environment when HTO was released to the atmosphere. We measu red the evolution of depth profiles of heavy water concentrations in s oil water and compared the reemission rates with the evaporation veloc ities to study the deposition and reemission of heavy water to/from so il. The depth profiles of heavy water concentrations in soil were expr essed by exponential functions of which the gradient depended on the d eposition period. The initial reemission rates of heavy water from the soil were the highest, regardless of the meteorological conditions. T he reemission occurred not only during the day but also at night, sugg esting that the exchange of heavy water in the soil surface layer with H2O in air played a dominant role during nighttime. (C) 1998 Elsevier Science S.A. All rights reserved.