Above-canopy mapping of elevated CO2 gradients from volcanic gas seeps in a Costa Rican rainforest using fixed-wing sUAS
Abstract
Persistent volcanic CO2 gas seeps are common on the broad slopes of active volcanoes and are often devoid of acid gases due to subsurface scrubbing. Small variations in excess diffuse soil CO2 flux can be diagnostic for volcano monitoring and early warning applications: Deep recharge of magmatic reservoirs, and magma ascent, are often heralded by increases in CO2 flux at these gas seeps, rather than from central vents. Variable structural conditions may express these continuous gas seeps as discrete or diffuse emissions. Anecdotal evidence of increased plant growth in the months to years before eruptions, have been speculated to be due to enhanced fertilization by elevated CO2 emissions. These emissions are not large enough to cause major adverse effects like tree kills but may enhance photosynthetic activity. At many tropical volcanoes with dense vegetation, however, these sites are difficult to find and access due to dense vegetation and the vast terrain of volcanic landscapes. Satellite remote sensing techniques lack the sensitivity and spatial resolution needed to detect these CO2 seeps and their variations through time. Airborne techniques offer solutions for routine or spot investigations of CO2 fluxes from these otherwise hidden gas seeps.
We deployed small unmanned aerial systems (sUAS) using a fixed-wing sUAS designed for autonomous operations and long endurance in extreme environments, without causing significant disturbance of the sampled air. We integrated an in-situ sensor to record the CO2 enhancement field above the forest canopy. Test flight results on the flanks of Turrialba volcano in Costa Rica above forest canopies covering known moderate gas seeps demonstrate the sUAS-borne detection and mapping capabilities of above-canopy elevated CO2 gradients. The strong detection capabilities and high detector signal stability resulted from key system design elements including RF shielding, mechanical stabilization, and calibration procedures. This highly robust system is readily applied for diffuse volcanic CO2 emission studies on active volcanoes covered by dense vegetation. This system is specifically designed to detect, map, and track diffuse volcanic CO2 gas seeps and their atmospheric gradients, on the forested flanks of tropical volcanoes. © California Institute of Technology- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.V23C..08S
- Keywords:
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- 1030 Geochemical cycles;
- GEOCHEMISTRY;
- 1031 Subduction zone processes;
- GEOCHEMISTRY;
- 8414 Eruption mechanisms and flow emplacement;
- VOLCANOLOGY;
- 8485 Remote sensing of volcanoes;
- VOLCANOLOGY