Tracer Applications of Noble Gas Radionuclides in the Geosciences

TL;DR

This paper reviews the use of noble gas radionuclides and the Atom Trap Trace Analysis technique in geosciences, highlighting recent advances, applications in dating and circulation studies, and advocating for dedicated ATTA facilities.

Contribution

It provides a comprehensive overview of ATTA technology and its applications in geosciences, emphasizing recent progress and future potential for routine measurements.

Findings

ATTA enables routine measurement of radiokrypton isotopes.

Noble gas radionuclides are valuable for dating and circulation studies.

Future development of dedicated ATTA facilities is recommended.

Abstract

The noble gas radionuclides, including 81Kr (half-life = 229,000 yr), 85Kr (11 yr), and 39Ar (269 yr), possess nearly ideal chemical and physical properties for studies of earth and environmental processes. Recent advances in Atom Trap Trace Analysis (ATTA), a laser-based atom counting method, have enabled routine measurements of the radiokrypton isotopes, as well as the demonstration of the ability to measure 39Ar in environmental samples. Here we provide an overview of the ATTA technique, and a survey of recent progress made in several laboratories worldwide. We review the application of noble gas radionuclides in the geosciences and discuss how ATTA can help advance these fields, specifically determination of groundwater residence times using 81Kr, 85Kr, and 39Ar; dating old glacial ice using 81Kr; and an 39Ar survey of the main water masses of the oceans, to study circulation pathways and estimate mean residence times. Other scientific questions involving deeper circulation of fluids in the Earth's crust and mantle also are within the scope of future applications. We conclude that the geoscience community would greatly benefit from an ATTA facility dedicated to this field, with instrumentation for routine measurements, as well as for research on further development of ATTA methods.