Final Activity Report Summary - VOLCANGAS (Volcanic gas and aerosol emissions: ground based remote sensing, atmospheric impact and modelling of magma degassing processes) The measurement of SO2 flux from volcanoes is of major importance for monitoring and hazard assessment purposes, and for evaluation of the environmental impact of volcanic emissions. We propose here a novel technique for accurate and high time resolution estimations of the gas flux. This method combines two wide field of view UV spectrometers which are capable of collecting, instantaneously, light from thin parallel cross sections of the whole gas plume, obviating the need for either traversing, scanning or imaging. It enables tracking of inhomogeneities in the gas cloud from which accurate evaluation of the plume velocity can be made by correlation analysis. The method has been successfully applied on Mt. Erebus (Antarctica), Kilauea (Hawaii) and Tungurahua (Ecuador) volcanoes. It yields estimations of the plume velocity and gas flux at unprecedented time resolution (1 Hz) and high accuracy.These measurements provide insight into the short-term variations of the degassing of these volcanoes with contrasting eruptive behaviours involving either passive or explosive degassing. Physical mechanisms are proposed to explain the observed degassing patterns. The dual-wide field of view DOAS technique promises better integration of geochemical and geophysical observations. It allows new insights into gas and magma dynamics, as well as processes of magma storage and gas segregation at active volcanoes.
