EVOLUTION OF HTO CONCENTRATIONS IN SOIL, VEGETATION AND AIR DURING ANEXPERIMENTAL CHRONIC HT RELEASE

A small experimental plot was continuously exposed to elevated levels of HT in air over a 12-day period to study the build up and steady-sta te concentrations of HTO in the environment. HTO concentrations in soi l, vegetation and air all showed similar dynamics, increasing graduall y over time with temporary decreases during and following rainfall. Th e relative magnitudes of the soil, vegetation and air concentrations d epended on the height at which the air and vegetation were sampled, th e depth at which the soil sample was taken and the soil depth over whi ch the plants drew their transpiration water. The system was at or nea r steady-state in the last two or three days of the release. When aver aged over an eight day interval that included periods of rain, the rat ios of HTO concentration in soil, foliage and air moisture to HT conce ntration in air (measured 20 cm above the ground) were typically 0.001 4, 0.0010 and 0.0011 (Bq/mL)/(Bq/m(3)) for a cultivated field.