USING GROUND PENETRATING RADAR TO INVESTIGATE VARIABILITY IN THE VERTICAL DISTRIBUTION OF BIOGENIC FREE-PHASE GAS IN A NORTHERN PEATLAND DUE TO CHANGES IN ATMOSPHERIC PRESSURE

Atmospheric pressure regulates biogenic gas emissions (mostly methane and carbon dioxide) from northern peatlands. However, recent conceptual models differ in how gas production and release occur in shallow (defined here as less than 1 m depth) versus intermediate to deep peat soils (i.e. more than 1 m depth). We used ground penetrating radar (GPR) measurements in conjunction with deformation rod data to non-invasively estimate the vertical distribution of free-phase gas and the dependence of this distribution on atmospheric pressure in a northern peatland. We found a negative linear relation between changes in free-phase gas content and changes in atmospheric pressure for shallow peat soils and a positive linear relation for deeper soils. Our results suggest that higher concentrations of free phase gas occur in the deeper peat than in the shallow and intermediate peat soils. While changes in atmospheric pressure result in changes in free phase gas concentration in the shallow and intermediate peat layers, little variation was measured in the deep peat layer. Our results suggest a relationship between free phase gas and depth that may be due to changes in peat properties or increasing water pressure with depth.