Thermal Ionization Mass Spectrometer (TIMS):
$250-$375 per sample. For information and detailed
prices, see, for example:
Geochemistry Lab at the University of Maryland
The alkali earth metal strontium (Sr) has four
naturally occurring stable isotopes: 84Sr,
Of these, 87Sr
is the only radiogenic isotope, produced through
the beta decay of 87Rb.
Consequently, the strontium present in nature
is the sum of that present when the earth was
created plus the daughter product from the decay
Variation in the relative abundance of 87Sr
is usually expressed using 87Sr/86Sr
ratios, since 86Sr
is an isotope with a constant abundance.
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The Sr ratios of natural waters are controlled
in large part by rock-water interactions. Chemical
reactions such as ion exchange and mineral dissolution
determine the Sr isotopic value of the fluid,
and mineral precipitation affects the Sr concentration.
Sr is normally reported as the absolute 87Sr/86Sr
ratio. However, like many other isotopes, variation
in the Sr isotope system can be expressed using
where the 87Sr/86Sr
ratio of seawater is the typical standard used.
Analysis of 87Sr/86Sr
ratios is done by thermal ionization mass spectrometry,
an important method for analysis of elements that
are not easily converted to a gas.
page for more information)
ratio is a useful indicator in groundwater studies
of source water/rock interactions. However, the
kinetics of chemical reactions and mineral precipitation
must be taken into account. A large number of
mineral phases can affect the 87Sr/86Sr
values in the water phase. Different minerals
release Sr at different rates and may have different
ratios. Flow rate and flow path are other important
factors to consider when attempting to interpret
value of any groundwater sample (McNutt 2000).
Sr closely mimics the behavior of Ca2+,
for example substituting for Ca2+
in the lattices of minerals and replacing Ca in
the cell walls of plants and animals. Because
of this, Sr isotope ratios are useful to trace
Ca sources and cycling in oceans, watersheds,
Sr isotopic analysis has some appreciable advantages:
- Sr does not fractionate appreciably during
chemical reactions (including phase changes,
chemical and biological processes, etc.); hence,
measured Sr ratios are good indicators of the
original source of Sr. Furthermore, Sr isotope
analysis uses the 88Sr/86Sr
ratio, which is constant, as an internal standard
to correct for fractionation during measurement.
Thus, even if fractionation naturally did occur
it would be corrected during measurement.
- The atmospheric concentration of Sr is very
low, so there is little risk of any atmospheric
contamination to a given Sr ratio and, therefore,
no atmospheric correction is required.
ratio analysis can be used:
- to obtain information on the provenance of
- to determine mixing relationships within bodies
- by measuring the 87Sr/86Sr
ratio of lake sediments, to determine the changes
in the source history of a drainage or watershed
- to determine controls on source contributions
to water bodies
- to trace nutrient pathways and availability
of nutrient pools in ecosystems
- to fingerprint and quantify the sources of
salinity in river systems (See SAHRA's project
on the Solute
Balance of the Rio Grande).
- to indicate preferential flowpaths within
groundwater systems (See Johnson
et al. abstract)
- Benson, L., and Z. Peterman, Carbonate deposition,
Pyramid Lake subbasin, Nevada: 3. The use of
values in carbonate deposits (tufas) to determine
the hydrologic state of paleolake systems, Palaeogeography,
Palaeoclimatology, Palaeoecology, 119, 201-213,
- Bouchard, D.P., D.S. Kaufman, A. Hochberg,
and J. Quade, Quaternary history of the Thatcher
Basin, Idaho, reconstructed from the 87Sr/86Sr
and amino acid composition of lacustrine fossils:
implications for the diversion of the Bear River
into the Bonneville Basin, Palaeogeography,
Palaeoclimatology, Palaeoecology, 141, 95-114,
- Clark, I., and P. Fritz, Environmental
Isotopes in Hydrogeology, Lewis Publishers,
Boca Raton, 1997.
- English, N.B., J. Quade, P.G. DeCelles and
C.N. Garzione, Geologic control of Sr and major
element chemistry in Himalayan Rivers, Nepal,
Geochimica et. Cosm. Acta, 64, 2549-2566,
- Faure, G., Principles of Isotope Geology,
2nd ed., John Wiley & Sons, New York, 1986.
- Gosz, J.R., and D.I. Moore, Strontium isotope
studies of atmospheric inputs to forested watersheds
in New Mexico, Biogeochemistry, 8, 115-134,
- Graustein, W.C., and R.L. Armstrong, The use
of strontium-87/strontium-86 ratios to measure
atmospheric transport into forested watersheds,
Science, 219, 289-293, 1983.
- Jones, L.M. and G. Faure, Strontium isotope
geochemistry of Great Salt Lake, Utah, Geo.
Society of Amer.Bulletin, 83, 1875-1880,
- Kendall, C., and J.J. McDonnell, editors,
Isotope Tracers in Catchment Hydrology,
Elsevier, NY, 1998.
- Mazor, E., Applied Chemical and Isotopic
Groundwater Hydrology, Halsted Press, 1991.
- McNutt, R.H., Strontium isotopes, in Envirionmental
Tracers in Subsurface Geology, ed. by P.G.
Cook and A.L. Herczeg, pp. 234-260. Kluwer,
- Miller, E.K., J.D. Blum, and A.J. Friedland,
Determination of soil exchangeable-cation loss
and weathering rates using Sr isotopes, (Letters
) Nature, 362, 438-441, 1993.
- Pedone, V.A., Negative covariance between
lake volume and strontium isotope ratio in the
Great Salt Lake, Utah, GSA Annual Meeting
Abstracts, Session 174, p. A-389, 2000.
- Quade, J., Strontium ratios and Lake Bonneville
chronostratigraphy, Late Quaternary Paleoecology
in the Bonneville Basin (Bulletin 130, Utah
Geological Survey), pp. 21-23, 2000.
- Quade, J., Strontium ratios and the origin
of early Homestead Cave biota, Late Quaternary
Paleoecology in the Bonneville Basin (Bulletin
130, Utah Geological Survey), pp. 44-46, 2000.
- Walker, F.W., J.P. Parrington, and F. Feiner,
Nuclides and Isotopes, 14th edition,
General Electric Company, San Jose, CA, 1989.
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T.M., et al, abstract of: Groundwater
"fast paths" in the Snake River Plain
aquifer: radiogenic isotope ratios as natural
groundwater tracers, Geology, 28(10):
Livermore National Laboratory, Isotope Sciences
of Kansas, Isotope Geochemistry Laboratory
Pitlab (Petrogenesis, Isotope Geology and Tectonics
Laboratory), Virginia Tech
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