Re: Naturally-occurring Tritium

["Strom, Daniel J" <daniel.j.strom@pnl.gov>]

Paul Lavely <lavelyp@uclink4.berkeley.edu> contributed this from the Miami
Tritium lab at http://www.rsmas.miami.edu/groups/tritium/ : "...'tagged' rain
water, and thereby all surface waters with HTO. This tracer perfectly follows
the water in atmospheric, oceanic and hydrological transport and mixing
processes."

I question the Miami Tritium Lab's claim that "this tracer perfectly follows the
water..." There is a well-known isotope effect when evaporating or boiling HTO
(molecular weight: 20) mixed with HHO (MW: 18). The lighter isotopes have a
higher vapor pressure at any particular temperature.  It is not hard to verify
in the lab, and is a several-percent effect when cryo-distilling a sample so
that 50% of the water remains behind and 50% is in the distillate. 

Water vapor above the open ocean, far from land, will have a lower concentration
of tritium than the seawater immediately below it. 

Tritium in exhaled breath water is also at a lower concentration than in body
water (e.g., urine or blood), partly due to the isotope effect and partly due to
the fact that some inspired water vapor is still in the expired air.

Moghissi,A.A.; Carter,M.W.  Tritium.  Phoenix, Arizona: Messenger Graphics;
1973.

Strom,D.J.; Bohner,K.R.  An Inexpensive and Practical Ambient-Temperature Vacuum
Still for Bioassays.  Health Phys.  56(3):355-359; 1989.

- Dan Strom

The opinions expressed above, if any, are mine alone and have not been reviewed
or approved by Battelle, the Pacific Northwest National Laboratory, or the U.S.
Department of Energy.

Daniel J. Strom, Ph.D., CHP
Risk Analysis & Health Protection Group, Environmental Technology Division,
Pacific Northwest National Laboratory
Mail Stop K3-56, PO BOX 999, Richland, Washington 99352-0999 USA
Telephone (509) 375-2626 FAX (509) 375-2019 mailto:daniel.j.strom@pnl.gov
Brief Resume: http://www.pnl.gov/bayesian/strom/strombio.htm
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