Methodological improvements and processing software of SO2 fluxes from UV cameras

With its high temporal and spatial resolution, SO₂ UV cameras are very attractive tools for monitoring emission and estimating fluxes (volcanic or anthropogenic sources). Their measurements can also contribute to warning systems (e.g., in the mitigation of volcanic crisis and its impact on aviation).

The first part of this contribution will briefly review the methodology with the pros and cons of this technique. In the calibration process (to obtain SO₂ amounts by using a collocated spectrometer as a part of our EnviCam3 SO₂ UV camera), we show means to mitigate some of the effect on UV light propagation (i.e., dilution and saturation) by using a multi-window DOAS analysis approach. We will show some tests of the saturation effect for sets of SO₂ concentrations (from 10 to 10000 ppm.m) obtained in our laboratory (device with a vacuum pump).

 In the second part, we will present a new GUI Python software developed at BIRA, for both fast analysis during field campaigns and more detailed post-processing analysis of SO₂ fluxes. The functionalities of this software consist of: 1) automatic or manual correction of X/Y shifts between the images from the two cameras; 2) correction of the vignetting effect in each image; 3) automatic detection of spectrometer field of view by correlation with time series of QDOAS retrieved SO₂ slant columns for calculating the conversion factor to SO₂ concentrations  4) estimation of the plume speed using optical flow computing; 5) retrievals of SO₂ fluxes (box, traverse or delta-M methods).

Data measured in the harbour of Antwerp (in 2022 and 2023), at Etna (in 2022) and Nyiragongo (in 2017) volcanoes will be shown.