Effect of UV scattering on SO₂ emission rate measurements

Abstract

[1] 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. Citation: Mori, T

Sulfur dioxide emissions during the 2011 eruption of Shinmoedake volcano, Japan

“…On February 13, SO 2 measurements aimed at the summit area of Shinmoedake volcano were conducted from 7 km distance using COMPUSS. Sulfur dioxide was not detected in the measurements, which supports that the SO 2 flux had decreased considerably by this day, even considering the underestimation of SO 2 attributable to dilution effects (Mori et al, 2006b;. Based on the observed data (Table 1), we inferred that flux decreased gradually from 700 ton/day to 200 ton/day during March 1-20, 2011.…”

Novel SO&lt;sub&gt;2&lt;/sub&gt; spectral evaluation scheme using the 360–390 nm wavelength range

“…Thus, radiation of shorter wavelengths is more likely to be scattered between instrument and plume than radiation of longer wavelengths. This socalled "radiation dilution" effect was already discussed in Moffat and Millan (1971) and modelled by Millan (1980), but in ground based DOAS measurements first observed by Mori et al (2006), who realized that the SO 2 column density (CD) retrieved from measured spectra depended on the wavelength range in which the evaluation took place. Especially for long distances between instrument and plume (i.e.…”

Tula industrial complex (Mexico) emissions of SO&lt;sub&gt;2&lt;/sub&gt; and NO&lt;sub&gt;2&lt;/sub&gt; during the MCMA 2006 field campaign using a mobile mini-DOAS system

“…The spectrometers used in this study have a spectral resolution of about 0.6 nanometers (nm) and spectral range of 280-420 nm for SO 2 and 336-480 nm for NO 2 . Similar equipments have been successfully used to quantify SO 2 emissions from volcanoes (Bobrowski et al, 2003;Edmonds et al, 2003;Galle et al, 2002;McGonigle et al, 2002;Mori et al, 2006;O'Dwyer et al, 2003), industries (McGonigle et al, 2004;Rivera et al, 2009) and urban areas .…”