The Measurement of Mass Independent Isotopic Compositions in Atmospheric Species as a New Indice of Global Processes

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This research project is focused on the measurement of stable isotope ratios in several important atmospheric gases, that is, ozone (O3), carbon dioxide (CO2), carbon monoxide (CO), and water (H2O) vapor. The previous NSF-supported project demonstrated from precise isotopic measurements of oxygen-17 and oxygen-18 in stratospheric ozone samples that a chemical link exists between stratospheric ozone and carbon dioxide. In addition, the results from this prior research revealed that stratospheric ozone is enriched in the two oxygen isotopes of O- 17 and O-18, and that this isotopic enrichment is transferred to CO2 by its reaction with excited oxygen atoms O(1D) derived from the photolysis of this isotopically enriched ozone. During the next three years this same research team will continue to expand their isotopic measurement program so as to isotopically analyze air samples collected from ground level to 30 km and from 68oN to the south pole. These measurements will address the questions of the global and altitudinal variations of the CO2-O3 interactions; the chemical and dynamical processes responsible for the observed isotopic fractionations of molecular oxygen (O2), O3, CO2, CO, nitrous oxide (N2O), and water vapor; the possibility of an unknown stratospheric source of N2O; and the potential utility of CO2 with its unique stratospheric isotopic signature for quantification of mesosphere-stratosphere- troposphere mixing. The gas samples will be collected in collaboration with a number of national and international scientists who are performing vertical atmospheric measurements with aircraft and balloon platforms, The samples will be analyzed with the isotope ratio mass spectrometers that are available in the Department of Chemistry at the University of California--San Diego. Two graduate students will participate in this research under the direct supervision of the senior scientist.