Effect of UV scattering on SO2 emission rate measurements

We report the quantitative evaluation of the UV scattering effect on the SO 2 emission rate measurement by the compact UV spectrometer system. Plume spectra were obtained simultaneously at three measuring points with different distance to the volcanic plume. The apparent absorbance decreases with increasing distance to the plume and the attenuation becomes stronger at shorter wavelength bands. In addition, the attenuation intensity depends on the SO 2 column concentration. The underestimation of the measured absorbance caused by the UV scattering leads to the underestimation of the SO 2 emission rate. The attenuation was not significant with any wavelength band (<±10%) at 0.6 km but was 35-50% with shorter wavelength band at 2.6 km distance. The UV scattering effect on the SO 2 emission rate estimation can be evaluated by the comparison of the emission rates calculated with different wavelength bands.

[1]  Sune Svanberg,et al.  Optical monitoring of volcanic sulphur dioxide emissions - comparison between four different remote-sensing spectroscopic techniques , 2002 .

[2]  The structure, dynamics, and chemical composition of noneruptive plumes from Mount St. Helens, 1980–1988 , 1992 .

[3]  J. Hirabayashi,et al.  Discharge rate of SO2 from Unzen Volcano, Kyushu, Japan , 1995 .

[4]  C. Oppenheimer,et al.  Monitoring SO2 emission at the Soufriere Hills Volcano: Implications for changes in eruptive conditions , 1998 .

[5]  A. J. Sutton,et al.  Implications for eruptive processes as indicated by sulfur dioxide emissions from Kı̄lauea Volcano, Hawai‘i, 1979–1997 , 2001 .

[6]  Clive Oppenheimer,et al.  Plume velocity determination for volcanic SO2 flux measurements , 2005 .

[7]  A. McGonigle,et al.  A miniaturised ultraviolet spectrometer for remote sensing of SO2 fluxes: a new tool for volcano surveillance , 2003 .

[8]  M. Millán,et al.  Remote sensing of air pollutants. A study of some atmospheric scattering effects , 1980 .

[9]  M M Millan,et al.  The applications of optical correlation techniques to the remote sensing of SO 2 plumes using sky light. , 1971, Atmospheric environment.

[10]  John N. Porter,et al.  Real-time measurement of volcanic SO2 emissions: validation of a new UV correlation spectrometer (FLYSPEC) , 2006 .

[11]  Keith A. Horton,et al.  Accurately measuring volcanic plume velocity with multiple UV spectrometers , 2006 .

[12]  Clive Oppenheimer,et al.  Automated, high time-resolution measurements of SO2 flux at Soufrière Hills Volcano, Montserrat , 2003 .

[13]  Tamsin A. Mather,et al.  Walking traverse and scanning DOAS measurements of volcanic gas emission rates , 2002 .

[14]  R. Hoff,et al.  Remote sensing of air pollutants by correlation spectroscopy--instrumental response characteristics. , 1978, Atmospheric environment.

[15]  M. Burton,et al.  Sulphur dioxide fluxes from Mount Etna, Vulcano, and Stromboli measured with an automated scanning ultraviolet spectrometer , 2003 .

[16]  A. McGonigle,et al.  Comparison of COSPEC and two miniature ultraviolet spectrometer systems for SO2 measurements using scattered sunlight , 2006 .

[17]  Christina A. Neal,et al.  Emission rates of sulfur dioxide and carbon dioxide from Redoubt Volcano, Alaska during the 1989-1990 eruptions , 1994 .