VIVEIROS, F., CARDELLINI, C., CHIODINI, G., SILVA, C., MORENO, L., MATIAS, D. (2021) – After three decades of soil CO2 flux studies on volcanic areas – challenges and potentialities, 1^st CCVG Virtual Workshop, 24-26 de maio.

​Soil CO₂ degassing have been used in volcanic-hydrothermal areas since the early nineties and have showed to be important tools for seismo-volcanic monitoring, geothermal prospection, geological mapping, estimation of the global carbon budget and public health risks assessment. Two main methodological approaches have been applied, but literature highlights the wider and global use of the accumulation chamber methodology. Uncertainty related with calibration and sampling strategies (e.g., irregular vs. regular grids, number of sampled points), procedures of data acquisition and treatment (used statistical tools) reveals that differences on total estimation may be significant and difficult comparison between datasets from different areas. In addition, and considering the significant impact that short and longterm meteorological variations may have on the soil degassing, spatial surveys should be carried out with similar meteorological conditions and considering the season, at least for temperate areas. Control points should be set up to evaluate the intra and inter-surveys variability. Data obtained at the degassing area that expanded in 2010 at Caldeiras da Ribeira Grande area (Fogo volcano, São Miguel, Azores) was used to highlight differences resulting from the applied grids, sampling procedures, time of the year and interpolation methods. The current study highlights the potentialities together with the ongoing challenges associated with the application of soil diffuse degassing studies in volcanic areas. Accounting with sampling and analytical uncertainties on the resulting degassing maps are some of the challenges faced by the CCVG community. This study attempts to contribute to the definition of best practices for soil CO₂ flux measurements and highlights their relevance on the CO₂ carbon global budget estimations.