Spatial variability in biogenic gas accumulations in peat soils is revealed by ground penetrating radar (GPR)

Abstract

We performed surface and borehole ground penetrating radar (GPR) tests, together with moisture probe measurements and direct gas sampling to detect areas of biogenic gas accumulation in a northern peatland. The main findings are: (1) shadow zones (signal scattering) observed in surface GPR correlate with areas of elevated CH4 and CO2 concentration; (2) high velocities in zero offset profiles and lower water content inferred from moisture probes correlate with surface GPR shadow zones; (3) zero offset profiles depict depth variable gas accumulation from 0–10% by volume; (4) strong reflectors may represent confining layers restricting upward gas migration. Our results have implications for defining the spatial distribution, volume and movement of biogenic gas in peatlands at multiple scales.