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Tritiated Water Movement in Semiconfined Growth Systems¹

ABSTRACT

Since its beta radiation will not penetrate the skin, the major hazard of tritium (³H) to man is via the food pathways. This investigation was designed to provide preliminary information on ³H behavior in the food pathways, which include soils and plants.

Each of six semi-confined growth systems contained four corn (Zea mays L.) plants grown on 0.1 m³ of a fertilized peat-sandperlite mixture. The bottom of each container and the surface of the growth medium was covered with plastic to prevent excessive loss of ³H due to evaporation or mass flow.

The growth medium in each system received a single surface application of 3 mCi of tritiated water (HTO), and was kept near field capacity by watering every 2 or 3 days. Pairs of systems were labeled at 7, 10, or 13 weeks maturation of the corn, and the rate of ³H removal at different stages of plant growth was determined.

Residence time of ³H in the growth medium was short. At maximum rates of withdrawal (transpiration), over 90% of the added ³H was removed within 1 week. The maximum amount of readily extractable ³H found in the plants was about 3% of the original application. This occurred 3 days after labeling and decreased to 0.1 to 0.3% in 2 weeks.

Key Words: Tritium • ³H • HTO • rate of dispersion

¹ Contribution from the UT-AEC Agricultural Research Laboratory, Oak Ridge, Tenn., operated by the Tennessee Agr. Exp. Sta. for the US Atomic Energy Commission under Contract no. AT-40-1-GEN-242. Published with the permission of the Dean of the University of Tennessee Agr. Exp. Sta., Knoxville.

² Assistant Professor of Soil Science, University of Tennessee, Oak Ridge 37830.

Received for publication August 4, 1971.