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On the conversion of tritium units to mass fractions for hydrologic applications

July 30, 2013

We develop a general equation for converting laboratory-reported tritium levels, expressed either as concentrations (tritium isotope number fractions) or mass-based specific activities, to mass fractions in aqueous systems. Assuming that all tritium is in the form of monotritiated water simplifies the derivation and is shown to be reasonable for most environmental settings encountered in practice. The general equation is nonlinear. For tritium concentrations c less than 4.5×1012 tritium units (TU) - i.e. specific tritium activities<5.3×1011 Bq kg-1 - the mass fraction w of tritiated water is approximated to within 1 part per million by w ≈ c×2.22293×10-18, i.e. the conversion is linear for all practical purposes. Terrestrial abundances serve as a proxy for non-tritium isotopes in the absence of sample-specific data. Variation in the relative abundances of non-tritium isotopes in the terrestrial hydrosphere produces a minimum range for the mantissa of the conversion factor of [2.22287; 2.22300].

Citation Information

Publication Year 2013
Title On the conversion of tritium units to mass fractions for hydrologic applications
DOI 10.1080/10256016.2013.766610
Authors David A. Stonestrom, Brian J. Andraski, Clay A. Cooper, Charles J. Mayers, Robert L. Michel
Publication Type Article
Publication Subtype Journal Article
Series Title Isotopes in Environmental and Health Studies
Series Number
Index ID 70040793
Record Source USGS Publications Warehouse
USGS Organization Branch of Regional Research-Western Region