Experimental design for measuring CO2 emissions from soils in the lower atmosphere using unmanned aerial vehicles

Carbon dioxide is considered to be an important greenhouse gas. The balance of sources and sinks governing the CO2 concentration in the atmosphere are of continuous scientific debate. One of the sources for atmospheric carbon dioxide are emissions from the soil, which can exist in several forms. Local variations can show anomalies with a significantly increased outflow of gas.

One such location lies in the valley of the Neckar river in Southwest Germany. In various areas carbon dioxide is leaking out of the ground in pure gaseous form, with concentrations of up to 95%, and as acidulous water. The source of the carbon dioxide may be of geological nature, but their exact origin is still unknown. The annual amounts of outflow and their significance on the atmosphere are so far unknown. However, the amounts have been considered significant enough to be exploited by the local mineral water industries until the late 1980s.

Research in this subject has subsided, following the decline of the industrial exploitation. Local reports since this time indicate a steady increase in outflow, with new outbursts observed, for example on a nearby golf course. Old installations of the industrial exploitation, like wells and pipes, still exist underground and their extent and influence on emissions seems to be also unknown.

Besides as a research subject for the geological origin of this phenomenon, the site also raises questions about the health and safety of the local human and animal population. So far there has been no significant research conducted on the subject of the transport and distribution of the emitted gases in the lower atmosphere.

Because of the distributed nature of this phenomenon, this study suggests the design of an unmanned airborne sensor system to investigate the distribution of carbon dioxide in the lower atmosphere. Using a low-cost sensor, a small unmanned aerial vehicle can quickly survey the local area. Challenges remaining are the sensitivity and temporal resolution of low-cost CO2 sensors, as well as the disturbance of the airflow by the aircraft itself.

In this presentation the results of a pre-study are shown, leading to the selection of a suitable sensor system and airframe as well as a possible measurement strategy.