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.