Simplified Method for the In Situ Collection and Laboratory Analysis of Cosmogenic Tracers (Sulfur-35 and Sodium-22) to Determine Residence Time Distributions and Water Ages

Amanda L Deinhart; Richard K Bibby; Ate Visser; Melissa Thaw; Keenan Thomas

doi:10.1021/acs.analchem.0c04490

Simplified Method for the In Situ Collection and Laboratory Analysis of Cosmogenic Tracers (Sulfur-35 and Sodium-22) to Determine Residence Time Distributions and Water Ages

Anal Chem. 2021 Mar 16;93(10):4472-4478. doi: 10.1021/acs.analchem.0c04490. Epub 2021 Mar 5.

Authors

Amanda L Deinhart¹, Richard K Bibby¹, Ate Visser¹, Melissa Thaw^{2

3}, Keenan Thomas¹

Affiliations

¹ Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, California 94550, United States.
² School of Engineering, University of California, Merced, Merced, California 95343, United States.
³ Bren School of Environmental Science & Management, University of California, Santa Barbara, Santa Barbara, California 93106, United States.

PMID: 33667067
DOI: 10.1021/acs.analchem.0c04490

Abstract

The use of cosmogenically produced sulfur-35 (T_1/2 = 87 days) and sodium-22 (T_1/2 = 2.6 years) as intrinsic tracers can provide valuable information on catchment hydrology, flow paths, and subsurface storage. A new and straightforward method was created to determine the activities of both ³⁵S and ²²Na in various water sources by pumping large volumes (up to 1000 L) of water through cation- and anion-exchange resin columns in the field to collect sodium and sulfate ions and simple chemistry in the lab. Samples are counted for ³⁵S using liquid scintillation counting (LSC) and for ²²Na via γ spectroscopy. Our novel in situ method provides faster sample throughput as well as better counting statistics and lower detection limits. Both methods were successfully applied at the Southern Sierra Critical Zone Observatory.