USING HIGH FREQUENCY GROUND PENETRATING RADAR (GPR) AT THE LABORATORY SCALE TO INVESTIGATE THE SPATIAL VARIABILITY IN RELEASES OF BIOGENIC GASES FROM THREE SUBTROPICAL WETLAND ECOSYSTEMS IN CENTRAL FLORIDA

Spatial Distribution of biogenic gas (CH_4, CO₂) production within peat soils remains highly uncertain despite the many studies surrounding peatland greenhouse gas production within the recent past. Majority of these studies have been focused in northern boreal peatlands leaving tropical and subtropical peatlands vastly understudied. This study implements hydrogeophysical methods to investigate the spatial variability in biogenic gas accumulation and release in three 0.027 m³ peat monoliths from three different wetland ecosystems in central Florida (sawgrass peatland, a wet prairie, and a depressional wetland within a pine flatwood). Gas content variability (i.e. build-up and release) within the peat matrix was estimated over a period of five months using a series of high frequency (1.2 GHz) ground penetrating radar (GPR) transects along each sample about three times a week. An array of gas traps (eight per sample) fitted with time-lapse cameras were used in order to constrain GPR measurements as well as 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. A grid of surface deformation points was also collected concurrently to monitor changes in the peat surface associated with gas build up and release. Cores were collected under each gas trap after GPR measurements concluded in order to analyze the peat soil for porosity and bulk density. The aim of this study is to investigate the spatial variability of biogenic gas production not only at the lab scale but also regionally by comparing monoliths from three different wetland ecosystems and how these differences are potentially related to structural changes within the peat matrix. This work has implications for better understanding natural greenhouse gas production as well as carbon dynamics within subtropical peat soils.