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Analytical Method for Measuring Cosmogenic (35)S in Natural Waters
Stephanie H Urióstegui1, Richard K Bibby2, Bradley K Esser2
1†Department of Earth Science, University of California, Santa Barbara, Santa Barbara, California 93106, United States.
Analytical Chemistry
|May 19, 2015
Summary
A new method analyzes more sulfate for cosmogenic sulfur-35 ((35)SO4), expanding its use as a hydrologic tracer. This technique works even in waters with high sulfate concentrations, overcoming previous limitations.
Area of Science:
- Environmental Science
- Hydrology
- Nuclear Chemistry
Background:
- Cosmogenic sulfur-35 ((35)SO4) is a valuable hydrologic tracer in low-sulfate environments.
- High sulfate concentrations limit the application of (35)SO4 due to analytical constraints with current liquid scintillation counting (LSC) techniques.
Purpose of the Study:
- To develop a new analytical method for quantifying (35)S in larger sulfate masses.
- To overcome the limitations of existing methods for analyzing (35)SO4 in high-sulfate waters.
Main Methods:
- Developed a method to analyze barium sulfate (BaSO4) precipitate for (35)S.
- Optimized BaSO4 suspension in Inta-Gel Plus cocktail for enhanced LSC efficiency.
- Purified BaSO4 to remove organic matter and used high-purity barium chloride to mitigate radium interference.
- Optimized LSC counting parameters for larger BaSO4 masses.
Main Results:
- Achieved comparable LSC counting efficiencies for (35)S despite a 10-fold increase in sulfate sample load.
- Successfully measured (35)SO4 in high-sulfate surface and groundwater samples.
- Demonstrated the method's effectiveness in samples with low (35)S activity to sulfate mass ratios.
Conclusions:
- The new analytical method significantly expands the usable range of (35)SO4 analysis.
- This advancement broadens the utility of (35)SO4 as an intrinsic hydrologic tracer in diverse aquatic environments, including those with high sulfate levels.
