Grant: $231,812 - National Science Foundation - Jun. 4, 2009
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Award Description: Noble gas radionuclides provide a new and previously unexplored tool that can help distinguish the origin of the atmospheric components associated with volcanic gases. In this project led by a beginning female investigator, we aim to measure these radionuclides in the depleted mantle volatile component (at the Rio Grande Rift) and in subduction zone volcanism (at Poas Volcano, Costa Rica) in order to constrain the possible fraction of subduction-derived noble gases (i) in the depleted mantle and (ii) in the volatile emissions of a subduction-zone volcano. This study is expected to bring new insights to the origin of terrestrial volatiles, evolution of the atmosphere and ocean, mantle heterogeneity, and surface-mantle volatile exchange. The sampling and analysis of noble gas radionuclides are challenging, and involve significant technical development. While the sampling method for these radionuclides in normal groundwater has already been established, geothermal gases often contain >99% of CO2 which dilutes the radionuclides, requiring us to sample 100-200 times more total gas. To assure that the required quantities of Kr (~50 µlSTP) and Ar (~500 ccSTP) are obtained, 10,000-20,000 liter STP of geothermal gas needs to be sampled. Based on the lessons learned from our first attempts at Yellowstone National Park and Valles Caldera, significant technical improvement is still required for efficient sampling. Several undergraduate students from the host and collaborating institutions, University of Illinois at Chicago and University of New Mexico (schools having some of the most diverse student populations in the nation), will participate in development and testing of the sampling apparatus as well as in field sampling. This project will also enhance international collaboration with geoscientists at the University of Costa Rica and the University of Bern.
Project Description: In this project, we aim to measure noble gas radionuclides in the depleted mantle volatile component (at the Rio Grande Rift) and in subduction zone volcanism (at Poas Volcano, Costa Rica) in order to constrain the possible fraction of subduction-derived noble gases (i) in the depleted mantle and (ii) in the volatile emissions of a subduction-zone volcano. In order to obtain sufficient quantities of noble gas radionudlides from the gas emanations of interest, a field sampling system has been developed and tested in the field. The main task was to efficiently remove CO2 that constitutes more than 99% of the gas emanation, and to minimize the mechanical failures caused by the chemically corrosive gas. For these purposes, sampling system was newly designed and built (i) using materials and parts specified as corrosion resistant, (ii) attempting to remove the corrosive gas component (H2S) close to the entrance of the vacuum line to minimize contact of corrosive gas with vacuum line parts, and (iii) enabling rapid re-generation of purification components (chemical traps and condensers). A field testing of the sampling system took place at Sulphur Springs, in Valles Caldera, New Mexico (within the Rio Grande Rift) between September 1 and 6, 2009. A female undergraduate student and a female technical staff member from UIC participated in this field study along with the PI and co-PI. While we experienced several mechanical failures for various causes (e.g. materials not meeting specification), triplicate samples of gas emanating from a single spring were successfully obtained. The analysis of the gas composition is underway at UNM (major components) and at Lawrence Berkeley National Laboratory (noble gases). Improved design of this sampling system is underway, involving another undergraduate student from UIC.
Jobs Summary: PI job retained as a Research Assistant Professor. Dr. Yokochi's salary support is entirely funded from this grant, for 6months each year, to be primarily responsible for designing and testing apparatus for field sampling, separations of Kr for atom-trap analysis, and data analysis and interpretation. (Total jobs reported: 1)
Project Status: Less Than 50% Completed
This award's data was last updated on Jun. 4, 2009. Help expand these official descriptions using the wiki below.