Hydrogeology

Peat soils are known to be a significant source of atmospheric greenhouse gasses. However, the releases of methane and carbon dioxide gasses from peat soils are currently not well understood, particularly since the timing of the releases are poorly constrained. Furthermore, most research work performed on peatlands has been focused on temperate to sub-arctic peatlands, while recent works have suggested that gas production rates from low-latitude peat soils are higher than those from colder climates. The purpose of the work proposed here is to introduce an autonomous Ground Penetrating Radar (GPR) method for investigating the timing of gas releases from peat soils at the lab scale utilizing samples originating from Maine and the Florida Everglades, and at the field scale in a Maine peatland. Geophysical data are supported by direct gas flux measurements using the flux chamber method enhanced by timelapse photography, and terrestrial LiDAR (TLS) monitoring surface deformation.

This thesis presents a preliminary study on geochemical conditions within the Snapper Creek well field in Miami-Dade County, Florida. The study investigates the background groundwater chemistry within the Biscayne aquifer in order to provide information on the geochemical processes and water-rock interactions within the study site. In conjunction with hydraulic gradient information, major ion chemistry and deuterium and oxygen-18 data were used as environmental tracers to help describe the groundwater-surface water interactions between the well field and the Snapper Creek canal. Hydrologic data show there is potential for natural groundwater recharge from the canal within the shallow flow zone of the Biscayne aquifer and chemical data show evidence of canal-groundwater mixing within this zone. The limitations for the v environmental tracers employed within the study are addressed, as well as recommendations for further research involving natural geochemical tracers and groundwater-surface water interactions near municipal well fields. This study was part of a larger effort being conducted by the U.S. Geological Survey in order to assess municipal well field pumping effects on the Snapper Creek (C-2) canal.