- 1International Atomic Energy Agency, Department of Nuclear Sciences and Applications, Division of Physical and Chemical Sciences, Isotope Hydrology Section, Vienna International Centre, PO Box 100, 1400, Vienna, Austria
- 2Helmholtz Centre for Environmental Research UFZ, Permoserstrasse 15, 04318 LEIPZIG, GERMANY
- 3Universitaetsklinikum Heidelberg, Im Neuenheimer Feld 672, HEIDELBERG 69120, GERMANY
- 4State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, CHINA
- 5Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550-9234, UNITED STATES OF AMERICA
Research on groundwater residence times is crucial for assessing groundwater infiltration rates and aquifer vulnerabilities, both playing a vital role in sustainable water resource management. This study aimed at advancing the use of the short-lived cosmogenic radionuclide 35S (“radio-sulfur”, t1/2 = 87.4 d) for determining groundwater residence times of less than one year. The results show that 35S provides a valuable tool for evaluating groundwater residence times, infiltration rates, and aquifer vulnerabilities. The preconcentration of 35SO42- using an anion exchange resin prior to Liquid Scintillation Counting (LSC) is a technique designed to improve the detection of 35S in groundwater and precipitation samples. Our optimized method involves a custom setup where up to 500 mg of SO42- can be extracted from a large-volume water sample in less than an hour by passing the sample through a column pre-packed with an ion exchange resin. The retained sulfate ions are then eluted and the eluate is subsequently concentrated by evaporating excess water, while ensuring the elimination of organic compounds resulting in the formation of a clear, colorless sample. Once all colored compounds are removed, the sample is mixed with a scintillation cocktail and analyzed using LSC. The SO42 preconcentration procedure has been adapted for application directly in the field and eliminates therefore the need to transport large volumes of water sample to the laboratory and addresses logistical challenges associated with shipping and storage. Furthermore, we explored various LSC optimization methods for the detection and quantification of 35S in natural water samples resulting in improvements of both background and efficiency during LSC measurement. This work represents advancements in the utilization of radio-sulfur analysis, thereby expanding the suite of natural radionuclides to constrain water residence time distributions in terrestrial waters.
How to cite: Wangari, S., Harjung, A., Machado, D., McGuire, B., Schubert, M., Kopitz, J., Lin, M., Copia, L., and Bibby, R.: Field sampling, sample preparation and measurement of radio-sulfur in natural water samples, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17720, https://doi.org/10.5194/egusphere-egu25-17720, 2025.
