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Assessment of a sequential phase extraction procedure for uranium-series isotope analysis of soils and sediments

Journal Article


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Abstract


  • The study of uranium-series (U-series) isotopes in soil and sediment materials has been proposed to quantify rates and timescales of soil production and sediment transport. Previous works have studied bulk soil or sediment material, which is a complex assemblage of primary and secondary minerals and organic compounds. However, the approach relies on the fractionation between U-series isotopes in primary minerals since they were liberated from the parent rock via weathering. In addition, secondary minerals and organic compounds have their own isotopic compositions such that the composition of the bulk material may not reflect that of primary minerals. Hence, there is a need for a sample preparation procedure that allows the isolation of primary minerals in soil or fluvial sediment samples. In this study, a sequential extraction procedure to separate primary minerals from soils and sediments was assessed. The procedure was applied to standard rock sample powders (TML-3 and BCR-2) to test whether it introduced any artefactual radioactive disequilibrium. A new step was introduced to remove the clay-sized fraction (<2 µm). Significant amounts (5–14%) of U and Th were removed from the rock standards during the procedure. No significant alteration in (234U/238U) and (230Th/238U) activity ratios of the rock standards occurred during the procedure. Aliquots of soil sample were subjected to the sequential extraction process to test how each step modifies the uranium-series activity ratios and mineralogy. Although no secondary minerals were detected in the unleached soil aliquots, the sequential leaching process removed up to 17% of U and Th and modified their activity ratios by up to 3%. The modification of the activity ratios poses a demand for careful means to avoid redistribution of isotopes back to the residual phase during phase extraction.

UOW Authors


  •   Suresh, P O. (external author)
  •   Dosseto, Anthony
  •   Handley, Heather K. (external author)
  •   Hesse, Paul P. (external author)

Publication Date


  • 2014

Citation


  • Suresh, P. O., Dosseto, A., Handley, H. K. & Hesse, P. P. (2014). Assessment of a sequential phase extraction procedure for uranium-series isotope analysis of soils and sediments. Applied Radiation and Isotopes, 83 47-55.

Scopus Eid


  • 2-s2.0-84887911973

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=2311&context=smhpapers

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers/1293

Number Of Pages


  • 8

Start Page


  • 47

End Page


  • 55

Volume


  • 83

Abstract


  • The study of uranium-series (U-series) isotopes in soil and sediment materials has been proposed to quantify rates and timescales of soil production and sediment transport. Previous works have studied bulk soil or sediment material, which is a complex assemblage of primary and secondary minerals and organic compounds. However, the approach relies on the fractionation between U-series isotopes in primary minerals since they were liberated from the parent rock via weathering. In addition, secondary minerals and organic compounds have their own isotopic compositions such that the composition of the bulk material may not reflect that of primary minerals. Hence, there is a need for a sample preparation procedure that allows the isolation of primary minerals in soil or fluvial sediment samples. In this study, a sequential extraction procedure to separate primary minerals from soils and sediments was assessed. The procedure was applied to standard rock sample powders (TML-3 and BCR-2) to test whether it introduced any artefactual radioactive disequilibrium. A new step was introduced to remove the clay-sized fraction (<2 µm). Significant amounts (5–14%) of U and Th were removed from the rock standards during the procedure. No significant alteration in (234U/238U) and (230Th/238U) activity ratios of the rock standards occurred during the procedure. Aliquots of soil sample were subjected to the sequential extraction process to test how each step modifies the uranium-series activity ratios and mineralogy. Although no secondary minerals were detected in the unleached soil aliquots, the sequential leaching process removed up to 17% of U and Th and modified their activity ratios by up to 3%. The modification of the activity ratios poses a demand for careful means to avoid redistribution of isotopes back to the residual phase during phase extraction.

UOW Authors


  •   Suresh, P O. (external author)
  •   Dosseto, Anthony
  •   Handley, Heather K. (external author)
  •   Hesse, Paul P. (external author)

Publication Date


  • 2014

Citation


  • Suresh, P. O., Dosseto, A., Handley, H. K. & Hesse, P. P. (2014). Assessment of a sequential phase extraction procedure for uranium-series isotope analysis of soils and sediments. Applied Radiation and Isotopes, 83 47-55.

Scopus Eid


  • 2-s2.0-84887911973

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=2311&context=smhpapers

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers/1293

Number Of Pages


  • 8

Start Page


  • 47

End Page


  • 55

Volume


  • 83