Predicting hot spots and hot moments of biogenic gas accumulation and release in a subtropical ecosystem using airborne ground-penetrating radar (GPR)
| Active Dates | 9/1/2021-8/14/2024 |
|---|---|
| Program Area | Environmental Systems Science |
Project Description
Predicting hot spots and hot moments of biogenic gas accumulation and release in a subtropical
ecosystem
using airborne ground-penetrating radar (GPR)
Dr. Xavier Comas, Florida Atlantic University (Principal Investigator)
Dr. Caiyun Zhang, Florida Atlantic University (Co-Investigator)
Dr. Neil Terry, USGS (Co-Investigator)
Dr. Angela Gallego-Sala, Exeter University (Collaborator)
Peat soils are large natural producers of biogenic greenhouse gases (like methane and carbon dioxide) that accumulate in the soil matrix to subsequently be released to the atmosphere. Remarkable advances have been made in the last few decades in predicting these carbon fluxes at a variety of spatial and temporal scales in peat soils; however, many uncertainties exist in regard to the spatial distribution of hot spots for biogenic gas accumulation and hot moments for the rapid release of biogenic gases. Imaging and identifying these areas is difficult since most methods either: (1) require disturbance to the soil and typically can only characterize isolated local conditions that may not be representative of the heterogeneous conditions in peat soils, or (2) have sampling volumes that are too large to properly capture hot spots of increased geochemical activity. In this two-year exploratory proposal we intend to use a prototype GPR unit mounted on a small unoccupied aircraft system (sUAS) to efficiently identify the presence of hot spots and hot moments for biogenic gas accumulation and release in subtropical peat soils of the Everglades and explore how certain physical (i.e. soil structure) and biochemical properties (i.e. metabolic pathway) may influence its dynamics.
We hypothesize that an airborne GPR system can be used to identify contrasts in relative dielectric permittivity associated with variable biogenic gas content within the soil, therefore allowing non-invasive upscaling of traditional ground-based measurements over larger areas and without being constrained by terrain roughness. We also hypothesize that the physical structure of the organic soil primarily dictates the distribution of hot spots and enables prediction of hot moments for gas release triggered by changes in certain environmental factors such as atmospheric pressure or water table elevation. Airborne datasets will be constrained with ground-based GPR, moisture probes, gas traps fitted with time-lapse cameras, and soil measurements along cores (i.e. porosity, hydraulic conductivity). Additionally, and to serve as a testing ground under this exploratory proposal, the study will include: 1) stable C isotope measurements of gas samples to further constrain rates of production and release inferred from the GPR and to test the presence of spatially variable dominant methanogenic pathways; 2) X-ray computed tomography measurements (via an Environmental Molecular Sciences Laboratory User proposal at the Pacific Northwest National Laboratory, PNNL) to further test the role of physical structure in the accumulation and release of biogenic gases; and 3) development of preliminary remote sensing models (using the inferred gas dynamics from the GPR datasets) that account for the presence of hot spots and hot moments and further upscale predictions to ultimately generate large scale (km) carbon flux maps that could be incorporated into regional models.
The proposed project will also train one graduate and one undergraduate student. Results and products will be made openly available through DOE’s ESS-DIVE data repository. This proposal will also build a unique multidisciplinary team with researchers from FAU and the USGS and initiate a collaboration with the Environmental Molecular Sciences Laboratory (EMSL) at PNNL while strengthening ongoing collaborations with investigators at University of Exeter (UK).
Dr. Xavier Comas, Florida Atlantic University (Principal Investigator)
Dr. Caiyun Zhang, Florida Atlantic University (Co-Investigator)
Dr. Neil Terry, USGS (Co-Investigator)
Dr. Angela Gallego-Sala, Exeter University (Collaborator)
Peat soils are large natural producers of biogenic greenhouse gases (like methane and carbon dioxide) that accumulate in the soil matrix to subsequently be released to the atmosphere. Remarkable advances have been made in the last few decades in predicting these carbon fluxes at a variety of spatial and temporal scales in peat soils; however, many uncertainties exist in regard to the spatial distribution of hot spots for biogenic gas accumulation and hot moments for the rapid release of biogenic gases. Imaging and identifying these areas is difficult since most methods either: (1) require disturbance to the soil and typically can only characterize isolated local conditions that may not be representative of the heterogeneous conditions in peat soils, or (2) have sampling volumes that are too large to properly capture hot spots of increased geochemical activity. In this two-year exploratory proposal we intend to use a prototype GPR unit mounted on a small unoccupied aircraft system (sUAS) to efficiently identify the presence of hot spots and hot moments for biogenic gas accumulation and release in subtropical peat soils of the Everglades and explore how certain physical (i.e. soil structure) and biochemical properties (i.e. metabolic pathway) may influence its dynamics.
We hypothesize that an airborne GPR system can be used to identify contrasts in relative dielectric permittivity associated with variable biogenic gas content within the soil, therefore allowing non-invasive upscaling of traditional ground-based measurements over larger areas and without being constrained by terrain roughness. We also hypothesize that the physical structure of the organic soil primarily dictates the distribution of hot spots and enables prediction of hot moments for gas release triggered by changes in certain environmental factors such as atmospheric pressure or water table elevation. Airborne datasets will be constrained with ground-based GPR, moisture probes, gas traps fitted with time-lapse cameras, and soil measurements along cores (i.e. porosity, hydraulic conductivity). Additionally, and to serve as a testing ground under this exploratory proposal, the study will include: 1) stable C isotope measurements of gas samples to further constrain rates of production and release inferred from the GPR and to test the presence of spatially variable dominant methanogenic pathways; 2) X-ray computed tomography measurements (via an Environmental Molecular Sciences Laboratory User proposal at the Pacific Northwest National Laboratory, PNNL) to further test the role of physical structure in the accumulation and release of biogenic gases; and 3) development of preliminary remote sensing models (using the inferred gas dynamics from the GPR datasets) that account for the presence of hot spots and hot moments and further upscale predictions to ultimately generate large scale (km) carbon flux maps that could be incorporated into regional models.
The proposed project will also train one graduate and one undergraduate student. Results and products will be made openly available through DOE’s ESS-DIVE data repository. This proposal will also build a unique multidisciplinary team with researchers from FAU and the USGS and initiate a collaboration with the Environmental Molecular Sciences Laboratory (EMSL) at PNNL while strengthening ongoing collaborations with investigators at University of Exeter (UK).
Award Recipient(s)
- Florida Atlantic University Boca Raton (PI: Comas, Xavier)
- USGS, United States Department of Interior (PI: Terry, Neil)