Dr. Vitchko Tsanev and Mr. Brian Jones from Cambridge University are visiting MVO this week to test, calibrate, and continue installation of the new Differential Optical Absorption Spectroscopy (DOAS) network. DOAS is used to measure the amount of sulphur dioxide (SO₂) coming out of the volcano.

DOAS is used for determining the amount of sulphur dioxide (SO₂) in a volcanic gas plume by measuring the intensity of ultraviolet light which has travelled through it. SO₂ absorbs light between 300 and 318 nanometres. The light that travels through SO₂ will be less in those wavelengths due to the absorption. The greater the absorption, the more SO₂ is present in the plume.

DOAS is the primary technique used by MVO to measure daily SO₂ flux rates, which are reported regularly in the Weekly Activity Reports. There are currently two active DOAS stations located at Broderick’s and Lover’s Lane, as indicated on the map. They are both located to the west of the volcano due to the prevailing east to west wind direction. Measurements are best taken when the sky is sunny and cloud-free, so that direct, rather than scattered, light is used. Additional spectrometers can be used as mobile units, able to be deployed to any accessible location suitable for taking measurements. This can be particularly useful if the permanent stations are covered in ash or if the plume is going in an unusual direction.

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