Developement of Tandem, Double-focusing, Electron Impact, Gas Source Mass Spectrometer for Measurement of Isotopologues in Geochemistry

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

This instrument development project will design and build a tandem, double-focusing, high-resolution, high-sensitivity, electron impact, gas source, mass spectrometer. The purpose of the instrument is to analyze rare, doubly-substituted isotopologues of gases occurring in volcanic plumes, geothermal hot springs, hydrocarbon reservoirs, deep crustal microbial communities, gas hydrates, soils, and Earth's atmosphere. The list of gases to be investigated with the proposed instrument includes N2 (15N15N), O2 (17O18O, 18O18O), CH4, N2O, SO2, and OCS but is not limited to them exclusively. The investigation of clumped isotope isotopologue distributions in naturally occurring samples confers the advantage of deriving information on temperature of synthesis of gas species from the measurement of a single phase. It is possible that kinetic isotope fractionation effects accompanying synthesis reactions may provide data on the prevalence of specific reaction mechanisms. An extensive program of experimental calibration will be required to assess both the geothermometric potential and kinetic isotope effects of clumped isotopologues with the new instrument. The expected outcome of use of the proposed instrument is to acquire a deeper understanding of present-day atmosphere-hydrosphere-lithosphere interactions. The improved knowledge of the modern world will then be used to develop calibrated interpretations of ancient atmospheric proxies in the geologic record. The ultimate goal is to understand the chemical evolution of Earth's atmosphere with as great a time resolution as permitted by available samples such as polar ice cores or rock strata. The use of a new mass spectrometer of unprecedented capability is likely to give rise to applications that cannot be predicted. In the context of broader impact on human society, the study of trace greenhouse gases such as CH4 and N2O will contribute to evaluating global warming and climate change.