Premium
Diurnal changes in volcanic plume chemistry observed by lunar and solar occultation spectroscopy
Author(s) -
Burton M. R.,
Oppenheimer C.,
Horrocks L. A.,
Francis P. W.
Publication year - 2001
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2000gl008499
Subject(s) - plume , volcano , occultation , water vapor , atmospheric sciences , dissolution , environmental science , geology , mineralogy , chemistry , meteorology , physics , geochemistry , astrophysics
We report the first spectroscopic measurements of volcanic gas emissions by lunar occultation. The experiment was carried out at Masaya volcano, Nicaragua in 1998 using a portable Fourier transform infrared spectrometer. Both SO 2 and HCl column concentrations were determined to yield a SO 2 /HCl molar ratio of 2.2±0.28 (±1σ). This is significantly greater than the equivalent ratio of 1.6±0.02 (±1σ) derived from solar occultation measurements of the volcanic plume. We propose that the cause of the nocturnal increase in SO 2 /HCl ratio is dissolution of HCl into volcanic water droplets within the plume. This arises because the low saturated vapour pressure of water by night results in strong condensation of plume water vapour whereas by day only negligible plume water vapour condenses.