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Issue 12, 2000
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Naturally occurring radioactive material consists of 238U, 235U and 232Th and series daughters; it is released into the environment from many anthropogenic sources. The use of quadrupole ICP-MS is well-suited to site investigations of releases of naturally occurring radioactive material through measurements of the ratios 232Th∶230Th, 230Th∶238U and 234U∶238U. Each ratio measurement may potentially indicate the contrast between the geochemical background and the affected environment. 232Th∶230Th was measured in samples prepared by fusion or selective extraction; Th was concentrated using TRU-Spec extraction resin and isotopic measurements were made with 5–10 µg Th. The precision is ≈1% (2σmean) and 10% for 232Th∶230Th of 1 000 and 100 000–200 000, respectively. Thorium isotopic measurements were applied to studies of accumulation of 230Th in phosphate-fertilized lawns. The ratio 230Th∶238U was determined via combining separate measurements of 230Th∶232Th and 232Th∶235U or 232Th∶238U; a 230Th∶238U precision of 1–2% (2σmean) is reported for a phosphate fertilizer sample. This 230Th∶238U measurement scheme requires no synthetic yield tracers, and is applied to studies of deposition of U mill tailings in an affected river basin. The ratio 234U∶238U was determined in natural waters following a two-stage extraction with Chelex 20 and UTEVA resins; a precision of ≈0.3–0.5% (2σmean) is attained for sample concentrates containing 15–25 µg U. 234U∶238U measurements are useful in distinguishing between dissolved U from natural weathering versus mining/milling sources.

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Article information

06 Mar 2000
29 Aug 2000
First published
10 Nov 2000

J. Anal. At. Spectrom., 2000,15, 1569-1573
Article type

Envirogeochemical exploration for "NORM" wastes: quadrupole inductively coupled plasma mass spectrometric measurements of thorium and uranium isotopes

M. E. Ketterer, J. A. Jordan, S. C. Szechenyi, D. D. Hudson and R. R. Layman, J. Anal. At. Spectrom., 2000, 15, 1569
DOI: 10.1039/B001787F

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