Measurement of volcanic SO2 fluxes with differential optical absorption spectroscopy

Measurements of volcanic sulphur dioxide fluxes are important indicators of volcanic activity and are crucial to understanding the impacts of volcanic emissions upon the environment and climate. For more than thirty years correlation spectrometers (COSPECs) have provided valuable service in this respect. However, given the vintage and operational costs of these devices, research groups and volcano observatories have recently begun using state of the art, lightweight, compact and inexpensive USB2000 ultraviolet spectrometers as a replacement technology, with differential absorption spectroscopy SO2 concentration retrievals. In order to widen the dissemination of the latter approach, an overview of this methodology is given here, covering hardware protocols and the use of freely available software, written for this purpose.