Measurements of Radionuclides

Abstract

Cosmogenic isotopes, described in Chapter 4 are very difficult to measure in natural archives. Because of the very low concentrations of the isotopes and high requirements to the accuracy of measured quantities, sophisticated and precise methods should be used. This chapter gives an overview of the details of cosmogenic isotope measurements. Cosmogenic isotopes, described in Chapter 4, are very difficult to measure in natural archives. Because of the very low concentrations of the isotopes and high requirements for the accuracy of measured quantities, sophisticated and precise methods should be used, especially for long-living and low-concentration isotopes such as beryllium-10 and chlorine-36. The modern measurement technique is based on the state-of-the-art AMS (acceleration mass spectrometry) method, as described in Section 5.1. Section 5.2 describes details of the measurements of radiocarbon 14C in tree rings, including annually resolved data, needed for the detection of past SEP events. Even more difficult are measurements of cosmogenic isotopes in ice cores (Section 5.3), because of the signal-to-noise ratio reaching the quantification limit and the hard-to-account-for effect of snow accumulation rate. Great details related to ice-core sample preparation for isotopic measurements are provided. We discuss that drilling site characteristics such as the accumulation rate must be known to determine the sampling strategy for 10Be and 36Cl measurements. Owing to these procedures, it is possible to achieve high-resolution and -quality measurements that allow us to investigate potential peaks that could indicate the occurrence of extreme SEPs.