title: On the conversion of tritium units to mass fractions for hydrologic applications.
abstract: 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 × 10(12) tritium units (TU) - i.e. specific tritium activities<5.3 × 10(11) 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].
authors: US Geological Survey, Menlo Park, CA, USA. dastones@usgs.gov
authors: David A
authors: DA
authors: Stonestrom
authors: Brian J
authors: BJ
authors: Andraski
authors: Clay A
authors: CA
authors: Cooper
authors: C Justin
authors: CJ
authors: Mayers
authors: Robert L
authors: RL
authors: Michel
mesh_terms: D003903:Deuterium / Q000032:analysis* / Q000737:chemistry; D060587:Groundwater / Q000737:chemistry*; D062070:Hydrology / Q000295:instrumentation / Q000379:methods*; D008956:Models, Chemical; D008970:Molecular Weight; D014316:Tritium / Q000032:analysis* / Q000737:chemistry; D014875:Water Pollutants, Radioactive / Q000032:analysis* / Q000737:chemistry
chemical_list: D014875:Water Pollutants, Radioactive; D014316:Tritium; D003903:Deuterium