Remote Sensing and CO2 Assesment

The principal objective of this study was to evaluate airborne remote sensing techniques in a natural analogue site to see if the natural gas vents could be indirectly detected through vegetation responses. For this, a series of airborne remote sensing flights acquired orthophotos, detailed topographic information and hyperspectral, thermal, and multispectral data over part of the collapsed volcanic caldera near Latera in central Italy. This is an area of pasture and cereal farming and woodland, where a number of well-characterised CO2 (and occasionally H2S) gas vents occur.

Hyperspectral techniques could detect plant stress and in some cases, this was subsequently verified as being attributable to gas vents.

Ground truthing for potential gas vents identified by remote sensing techniques.

Following detailed interpretation of all the datasets, 80 ‘anomalous’ areas were identified and approximately half of these were subsequently verified by detailed in situ and laboratory-based soil gas geochemical analyses. Anomalies in an area of sloping terrain could not be attributed to gas vents. However, the techniques also identified anomalies that could not be attributed to gas vents and future work should focus on reducing the number of false positive results.

Thermal data were able to detect some anomalies in areas of no vegetation (ploughed fields). However, the presence of H2S in some gas vents remains a complicating factor which must be addressed in future research, as H2S may cause significant stress on plants as well.

High quality orthophotos proved invaluable in aiding interpretation of other datasets.