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A Compilation of Sulfur Dioxide and Carbon Dioxide Emission-Rate Data from Mount St. Helens During 1980-88

U.S. Geological Survey Open-File Report 94-212
Version 1.0

By Kenneth A. McGee and Thomas J. Casadevall

1994

Airborne monitoring of Mount St. Helens by the USGS began in May 1980 for sulfur dioxide emissions and in July 1980 for carbon dioxide emissions. A correlation spectrometer, or COSPEC, was used to measure sulfur dioxide in Mount St. Helens' plume. The upward-looking COSPEC was mounted in a fixed- wing aircraft and flown below and at right angles to the plume. Typically, three to six traverses were made underneath the plume to determine the SO2 burden (concentration x pathlength) within a cross- section of the plume. Knowing the burden along with the plume width and plume velocity (assumed to be the same as ambient wind speed), we could then calculate the emission rate of SO2. The use of correlation spectroscopy for determining the sulfur dioxide output of volcanoes is well established and the technique has been discussed in detail by a number of investigators.

Carbon dioxide in the Mount St. Helens plume was measured by an infrared spectrometer tuned to the 4.26 μm CO2 absorption band. An external sample tube was attached to the fuselage of a twin-engine aircraft to deliver outside air to the gas cell of the spectrometer. The aircraft was then flown at several different elevations through the plume at right angles to plume trajectory to define plume area and carbon dioxide concentration in a vertical cross-section of the plume. These two parameters along with the density of CO2 for the altitude of the plume and the plume velocity (assumed as above to be equal to ambient wind speed) were then used to calculate the CO2 emission rate.

CONTENTS

1. README - Text file
2. Contents - Text file
3. Metadata
4. Open-File Report 94-212 - HTML file
5. Open-File Report 94-212 - Text file

This open-file report is available for purchase from:

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Federal Center, Denver, CO 80225
telephone: 303-202-4210; e-mail: infoservices@usgs.gov

DISCLAIMERS

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although all data and software released with this open file have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and (or) the functioning of the software.

U.S. Department of Interior, U.S. Geological Survey
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Last modified: 03.01.01 (krw)