Kammann et al. 2001

Kammann C, Grünhage L, Jäger H-J. 2001. A new sampling technique to monitor concentrations of CH4, N2O and CO2 in air at well-defined depths in soils with varied water potential. European Journal of Soil Science 52: 297-303.

These authors invented a buried probe based on silicone tubing for long-term monitoring of soil gas concentrations. In essence, this is simply a length of silicone tubing coiled into a flat “snail” shape and secured with wire mesh, with silicone stoppers at both ends. One end is penetrated by a stainless steel tube that extends to the surface, and is topped with a stopcock that allows sampling by syringe. These authors tested their design in a few laboratory and field studies, and demonstrated the gases CH4, N2O and CO2 do indeed diffuse into the hollow interior of the probe, and reach 95% equilibration in as little as 7 hours. They state the advantages of their design over other soil gas probes, most notably the ability to use this design in very wet and saturated soils, which is where CH4 processes may be of greatest interest.

The downside of this probe design from my point of view is the need to dig a pit for these probes, and the consequent long wait before the disturbance has dissipated and accurate sampling can begin. However, for long-term monitoring of soil gas processes, particularly in wetlands and soils prone to heavy rainfall events, these probes appear to be very useful.