Airborne detection of SO2 gas using an FTIR spectrometer
View of Pu`u `O`o is toward the
Photograph by K.A. McGee on
September 19, 1995
The volcanic gas plume from the Pu`u `O`o cinder-and-spatter cone (right) provided
the ideal testing ground for measuring SO2
with a prototype
Fourier transform infrared spectrometer (FTIR) made to USGS specifications.
The FTIR was mounted in an airplane configured for sampling outside air and
then flown through the plume about 1 km downwind from the Pu`u `O`o vent. Eight
traverses were made through the plume at different elevations. A COSPEC
was used simultaneously to check the FTIR results.
Sketch of the plume downwind from Pu`u `O`o on 19 September 1995 showing the
concentration (ppm) of sulfur dioxide gas measured by the prototype FTIR.
The view is upwind toward Pu`u `O`o into the page. Winds were from the
northeast at about 20 km/hr. An emission rate of 2,160 tonnes/day of SO2
was calculated from these measurements. This rate agrees closely with
measurements made by a COSPEC, the traditional method for measuring
McGee, K.A., and Gerlach, T.M., 1998, Airborne volcanic plume
measurements using a FTIR spectrometer, Kilauea volcano, Hawaii: Geophysical
Research Letters, vol. 25, n. 5, p. 615-618.
Methods of monitoring volcanic gases