High Temporal Resolution Measurements to Investigate Carbon Dynamics in Subtropical Peat Soils Using Automated Ground Penetrating Radar (GPR) Measurements at the Laboratory Scale

Abstract:

Peatlands have the capability to produce and release significant amounts of free phase biogenic gasses (CO₂, CH₄) into the atmosphere and are thus regarded as key contributors of greenhouse gases into the atmosphere. Many studies throughout the past two decades have investigated gas flux dynamics in peat soils; however a high resolution temporal understanding in the variability of these fluxes (particularly at the matrix scale) is still lacking. This study implements an array of hydrogeophysical methods to investigate the temporal variability in biogenic gas accumulation and release in high resolution for a large 0.073 m³ peat monolith from the Blue Cypress Preserve in central Florida. An autonomous rail system was constructed in order to estimate gas content variability (i.e. build-up and release) within the peat matrix using a series of continuous, uninterrupted ground penetrating radar (GPR) transects along the sample. This system ran non-stop implementing a 0.01 m shot interval using high frequency (1.2 GHz) antennas. GPR measurements were constrained with an array of 6 gas traps fitted with time-lapse cameras in order to capture gas releases at 15 minute intervals. A gas chromatograph was used to determine CH₄ and CO₂ content of the gas collected in the gas traps. The aim of this study is to investigate the temporal variability in the accumulation and release of biogenic gases in subtropical peat soils at the lab scale at a high resolution. This work has implications for better understanding carbon dynamics in subtropical freshwater peatlands and how climate change may alter such dynamics.