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Title: Measuring temporal variability in biogenic gas content in peat soils using moisture probes.
Creator: Heij, Gerhard, Comas, Xavier
Date Issued: 2012-04-06
PURL: http://purl.flvc.org/fcla/dt/3348827
Subject Headings: Peatlands, Carbon cycle, Soil science, Environmental conditions, Geosciences, Soil moisture, Soils --analysis, Biogenic gas
Format: Document (PDF)

Title: Determining peat thickness in subtropical peatlands using ground penetrating radar.
Creator: McNabb, Tyler, Comas, Xavier, Sumner, David
Date Issued: 2012-04-06
PURL: http://purl.flvc.org/fcla/dt/3349032
Subject Headings: Environmental geology, Earth sciences, Natural resources, Peatlands, Stratigraphy
Format: Document (PDF)

Title: Using hydrologic measurements to investigate free-phase gas ebullition in a Maine peatland, USA.
Creator: Bon, C. E., Reeve, A. S., Slater, L., Comas, Xavier
Date Issued: 2014-03-10
PURL: http://purl.flvc.org/fau/fd/FAUIR000132
Format: Citation

Title: The Effect of Fractures on Weathering of Igneous and Volcaniclastic Sedimentary Rocks in the Puerto Rican Tropical Rain Forest.
Creator: Hynek, Scott, Comas, Xavier, Brantley, Susan L.
Date Issued: 2017
PURL: http://purl.flvc.org/fau/flvc_fau_islandoraimporter_10.1016_j.proeps.2017.01.001_1642176259
Format: Document (PDF)

Title: Imaging tropical peatlands in Indonesia using ground-penetrating radar (GPR) and electrical resistivity imaging (ERI): implications for carbon stock estimates and peat soil characterization.
Creator: Comas, Xavier, Terry, N., Slater, L., Warren, M., Kolka, R., Kristiyono, A., Sudiana, N., Nurjaman, D., Darusman, T.
Date Issued: 2015-05-21
PURL: http://purl.flvc.org/fau/fd/FAUIR000133
Format: Citation

Title: CHANGES IN PHYSICAL PROPERTIES OF THE PEAT SOIL MATRIX ACROSS A SALINITY GRADIENT IN THE EVERGLADES: IMPLICATIONS FOR ACCELERATING PEAT COLLAPSE DURING SEA LEVEL RISE.
Creator: Florey, Maxwell, Comas, Xavier, Florida Atlantic University, Department of Geosciences, Charles E. Schmidt College of Science
Abstract/Description: Peatlands are areas with an accumulated layer of peat soil that are considered global stores of carbon, acting as a net sink of carbon dioxide and a net source of methane. Recent studies in coastal peatlands have shown how that a rise in sea level may contribute to the degradation of peat soils due to the inland progression of the saltwater interface, which may result in physical changes within the peat matrix that may eventually result in peat collapse. For example, earlier studies in boreal...
Show morePeatlands are areas with an accumulated layer of peat soil that are considered global stores of carbon, acting as a net sink of carbon dioxide and a net source of methane. Recent studies in coastal peatlands have shown how that a rise in sea level may contribute to the degradation of peat soils due to the inland progression of the saltwater interface, which may result in physical changes within the peat matrix that may eventually result in peat collapse. For example, earlier studies in boreal peat soils described the effect of pore dilation as a result of increased salinity in peat soils, while recent studies in Everglades peat soils showed specific salinity thresholds that may represent a permanent loss of the structural integrity of the peat matrix that may represent early stages of peat collapse. While most of these previous efforts have focused on drivers, recent work has also explored conceptual models to better understand the mechanisms inducing peat collapse. However, few datasets exists that consistently compare differences in physical properties under different in‐situ salinity conditions. In this study differences in the physical properties of peat soils across a salinity gradient along the western edge of Big Cypress National Preserve are investigated to test how differences in salinity may induce physical changes in the soil matrix. The physical properties targeted for this study include porosity, hydraulic conductivity, and carbon content. Measurements are conducted at the laboratory scale using peat cores and monoliths collected at selected locations to investigate: 1) how overall soil physical properties change spatially over a salinity gradient at the km scale moving from permanently saline to freshwater conditions; and 2) how physical properties change spatially at specific sites as dependant on vegetation boundaries and proximity to collapsed soils. This study has implications for better understanding the potential relation between physical changes of the soil matrix and the phenomena of peat collapse in the Everglades as saltwater intrusion progresses inward and alters freshwater ecosystems. Furthermore, a better mechanistic understanding of the peat collapse phenomenon can potentially help mitigate its occurrence.
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Date Issued: 2021
PURL: http://purl.flvc.org/fau/fd/FA00013809
Subject Headings: Peat soils, Salinity, Sea level, Big Cypress National Preserve (Fla.), Everglades (Fla.)
Format: Document (PDF)

Title: INVESTIGATING THE EFFECTS OF SEA-LEVEL RISE AND INCREASED SALINITY ON PEAT SOILS OF THE EVERGLADES (FLORIDA): IMPLICATIONS FOR CHANGES IN BIOGENIC GAS DYNAMICS AND PEAT COLLAPSE.
Creator: Sirianni, Matthew J., Comas, Xavier, Florida Atlantic University, Department of Geosciences, Charles E. Schmidt College of Science
Abstract/Description: While repeated transgressive and regressive sea level cycles have shaped south Florida throughout geological history, modern rates of sea level rise pose a significant risk to the structure and function of the freshwater wetland ecosystems throughout the low-lying Everglades region. Current regionally corrected sea level projections for south Florida indicate a rise of 0.42m by 2050 and 1.15m by 2100, suggesting the salinization of previously freshwater areas of the Everglades is conceivable....
Show moreWhile repeated transgressive and regressive sea level cycles have shaped south Florida throughout geological history, modern rates of sea level rise pose a significant risk to the structure and function of the freshwater wetland ecosystems throughout the low-lying Everglades region. Current regionally corrected sea level projections for south Florida indicate a rise of 0.42m by 2050 and 1.15m by 2100, suggesting the salinization of previously freshwater areas of the Everglades is conceivable. As freshwater areas become increasingly exposed to saltwater they experience shifts in vegetation composition, soil microbial populations, plant productivity, and physical soil properties that ultimately result in a phenomenon called peat collapse. Recent work in the Everglades has sought to further explain the mechanisms of peat collapse, however the physical changes to the peat matrix induced by saltwater intrusion are still uncertain. Moreover, the combination of physical alterations to the peat matrix associated with peat collapse and shifts in wetland salinity regimes will also likely disrupt the current carbon gas dynamics of the Everglades.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013589
Subject Headings: Sea level rise, Peat soils, Everglades (Fla)
Format: Document (PDF)

Title: Understanding Variability of Biogenic Gas Fluxes from Peat Soils at High Temporal Resolution Using Capacitance Moisture Probes.
Creator: Munzenrieder, Cali, Comas, Xavier, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Geosciences
Abstract/Description: Peatlands act as carbon sinks while representing major sources of biogenic gases such as methane (CH4) and carbon dioxide (CO2), two potent greenhouse gases. Gas production and release in these peats soils are also influenced by overall warm temperatures and water table fluctuations due to the naturally shallow water table in the Florida Everglades. Releases of biogenic gases from Florida Everglades peat soils are not well understood and the temporal distribution and dynamics are uncertain....
Show morePeatlands act as carbon sinks while representing major sources of biogenic gases such as methane (CH4) and carbon dioxide (CO2), two potent greenhouse gases. Gas production and release in these peats soils are also influenced by overall warm temperatures and water table fluctuations due to the naturally shallow water table in the Florida Everglades. Releases of biogenic gases from Florida Everglades peat soils are not well understood and the temporal distribution and dynamics are uncertain. The general objective of this work was geared towards a methodological approach which aimed to examine the feasibility of capacitance moisture probes to investigate biogenic gas dynamics in various Florida Everglades peat soils at high temporal resolution. This work has implications for establishing capacitance moisture probes as a method to monitor gas dynamics in peat soils at high temporal resolution and better understanding patterns of gas build-up and release from peat soils in the Everglades.
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Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004700
Subject Headings: Everglades National Park (Fla.) -- Environmental conditions, Gas dynamics, Geographic information systems, Grassland ecology, Greenhouse gases, Wetland ecology
Format: Document (PDF)

Title: Investigating biogenic gas dynamics from peat soils of the Everglades using hydrogeophysical methods.
Creator: Wright, William J., Comas, Xavier, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Geosciences
Abstract/Description: Peat soils are known to be a significant emitter of atmospheric greenhouse gasses. However, the spatial and temporal variability in production and release of greenhouse gases (such as methane) in peat soils remains uncertain, particularly for low-latitude peatlands like the Florida Everglades, as the majority of studies on gas dynamics in peatlands focus on northern peatlands. The purpose of the work outlined here is focused on understanding the spatial and temporal variability in biogenic...
Show morePeat soils are known to be a significant emitter of atmospheric greenhouse gasses. However, the spatial and temporal variability in production and release of greenhouse gases (such as methane) in peat soils remains uncertain, particularly for low-latitude peatlands like the Florida Everglades, as the majority of studies on gas dynamics in peatlands focus on northern peatlands. The purpose of the work outlined here is focused on understanding the spatial and temporal variability in biogenic gas dynamics (i.e. production and release of methane and carbon dioxide) by implementing various experiments in the Florida Everglades at different scales of measurement, using noninvasive hydrogeophysical methods. Non-invasive methods include ground-penetrating radar (GPR), gas traps, time-lapse cameras, and hydrostatic pressure head measurements, that were constrained with direct measurements on soil cores like porosity, and gas composition using gas chromatography. By utilizing the measurements of in-situ gas volumes, we are able to estimate gas production using a mass balance approach, explore spatial and temporal variabilities of gas dynamics, and better constrain gas ebullition models. A better understanding of the spatial and temporal variability in gas production and release in peat soils from the Everglades has implications regarding the role of subtropical wetlands in the global carbon cycle, and can help providing better production and flux estimates to help global climate researchers improve their predictions and models for climate change.
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Date Issued: 2018
PURL: http://purl.flvc.org/fau/fd/FA00013146
Subject Headings: Peat soils, Gas dynamics, Carbon cycle (Biogeochemistry), Everglades (Fla), Biogenic gas
Format: Document (PDF)

Title: High Spatial Resolution Measurements Using Hydrogeophysical Methods Reveal the Presence of Hotspots forBbiogenic Gas Accumulation and Release in the Florida Everglades.
Creator: Bole, Troy, Comas, Xavier, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Geosciences
Abstract/Description: It is well known that biogenic gas emissions (mainly methane and carbon dioxide) vary both spatially and temporally in peatlands. While most studies have focused on northern systems, several recent studies in tropical and subtropical peatlands (like the Everglades) have revealed the presence of areas of increased gas accumulation and emissions, or hotspots, that may be related to physical and/or biogeochemical changes within the peat's matrix. However, these studies are often limited in terms...
Show moreIt is well known that biogenic gas emissions (mainly methane and carbon dioxide) vary both spatially and temporally in peatlands. While most studies have focused on northern systems, several recent studies in tropical and subtropical peatlands (like the Everglades) have revealed the presence of areas of increased gas accumulation and emissions, or hotspots, that may be related to physical and/or biogeochemical changes within the peat's matrix. However, these studies are often limited in terms of sampling volume and resolution or are based in laboratory studies that may not be totally representative of field conditions. In this study we investigate the spatial variability (both lateral and vertical) in gas accumulation and release at the field scale, over 10 m long transects at two locations in Water Conservation Area 1 of the Florida Everglades, using an array of hydrogeophysical methods. Resulting data infers the presence of hotspots with dimensions ranging from 1-2 m in width and approximately 0.5 m tall. These areas showed high variations in biogenic gas accumulation and release an order of magnitude higher than surrounding areas and occur seasonally as the highest gas releases were observed during Florida’s wet season. This study therefore has implications for better understanding the spatial and temporal variability of biogenic gas hotspots in peat soils, and how the matrix structure affects gas accumulation and release. This study shows the importance of considering the heterogenous nature of the peat's matrix when quantifying gas fluxes in the Everglades, and particularly when using methods with small sampling volumes like gas chambers.
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Date Issued: 2019
PURL: http://purl.flvc.org/fau/fd/FA00013189
Subject Headings: Everglades (Fla. ), Biogenic gas, Peatlands, Measurement
Format: Document (PDF)

Title: Multi-scale characterization of dissolution structures and porosity distribution in the upper part of the Biscayne aquifer using ground penetrating radar (GPR).
Creator: Mount, Gregory J., Comas, Xavier, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Geosciences
Abstract/Description: The karst Biscayne aquifer is characterized by a heterogeneous spatial arrangement of porosity, making hydrogeological characterization difficult. In this dissertation, I investigate the use of ground penetrating radar (GPR), for understanding the spatial distribution of porosity variability in the Miami Limestone presented as a compilation of studies where scale of measurement is progressively increased to account for varying dimensions of dissolution features. In Chapter 2, GPR in zero...
Show moreThe karst Biscayne aquifer is characterized by a heterogeneous spatial arrangement of porosity, making hydrogeological characterization difficult. In this dissertation, I investigate the use of ground penetrating radar (GPR), for understanding the spatial distribution of porosity variability in the Miami Limestone presented as a compilation of studies where scale of measurement is progressively increased to account for varying dimensions of dissolution features. In Chapter 2, GPR in zero offset acquisition mode is used to investigate the 2-D distribution of porosity and dielectric permittivity in a block of Miami Limestone at the laboratory scale (< 1.0 m). Petrophysical models based on fully saturated and unsaturated. water conditions are used to estimate porosity and solid dielectric permittivity of the limestone. Results show a good correspondence between analytical and GPR-based porosity estimates and show variability between 22.0-66.0 %. In Chapter 3, GPR in common offset and common midpoint acquisition mode are used to estimate bulk porosity of the unsaturated Miami Limestone at the field scale (10.0-100.0 m). Estimates of porosity are based on the assumption that the directly measured water table reflector is flat and that any deviation is attributed to changes in velocity due to porosity variability. Results show sharp changes in porosity ranging between 33.2-60.9 % attributed to dissolution areas. In Chapter 4, GPR in common offset mode is used to characterize porosity variability in the saturated Biscayne aquifer at 100-1000 m field scales. The presence of numerous diffraction hyperbolae are used to estimate electromagnetic wave velocity and asses both horizontal and vertical changes in porosity after application of a petrophysical model. Results show porosity variability between 23.0-41.0 % and confirm the presence of isolated areas that could serve as enhanced infiltration or recharge. This research allows for the identification and delineation areas of macroporosity areas at 0.01 m lateral resolution and shows variability of porosity at different scales, reaching 37.0 % within 1.3 m, associated with areas of enhanced dissolution. Such improved resolution of porosity estimates can benefit water management efforts and transport modelling and help to better understand small scale relationships between ground water and surface water interactions.
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Date Issued: 2014
PURL: http://purl.flvc.org/fau/fd/FA00004143
Subject Headings: Ground penetrating radar, Limestone -- Florida -- Miami Dade County -- Analysis, Physical geology, Sedimentary basins -- Florida -- Biscayne Aquifer, Sedimentation analysis
Format: Document (PDF)

Title: IDENTIFICATION OF SURFACE DEPRESSIONAL FEATURES POTENTIALLY RELATED TO SINKHOLES IN MARTIN COUNTY, FLORIDA, USING REMOTE SENSING TECHNIQUES.
Creator: Sanju, Khatri, Comas, Xavier, Florida Atlantic University, Department of Geosciences, Charles E. Schmidt College of Science
Abstract/Description: Sinkholes are common karst features in Florida, having the highest rate of sinkhole occurrence in the US, which results in hundreds of millions estimated costs in damage per year and occasional life losses. While most sinkhole incidents reported in Florida relate to surface subsidence and collapse processes, other sinkhole formation mechanisms (like sagging) have received little attention as a relevant subsidence process. This is important since extensive areas of karst bedrock are overlain...
Show moreSinkholes are common karst features in Florida, having the highest rate of sinkhole occurrence in the US, which results in hundreds of millions estimated costs in damage per year and occasional life losses. While most sinkhole incidents reported in Florida relate to surface subsidence and collapse processes, other sinkhole formation mechanisms (like sagging) have received little attention as a relevant subsidence process. This is important since extensive areas of karst bedrock are overlain by variable thicknesses of non-soluble formations that may affect both the kinematics and damaging potential of these sinkholes in Florida. This research presents an automated GIS-based method to easily delineate surface depressional features in Martin County that result in surface depressional features and are related to cover sagging sinkholes. A total of 3,091 depressional features in Martin County were mapped using GIS methods and constrained with already existing direct drill cores. Results show a consistent statistically significant negative correlation between several morphometric features (i.e., area, perimeter, or depth) from these depressional features and depth to the limestone, suggesting that depressions are linked to sinkholes developed in deep-seated karst. While further subsurface imaging is needed to confirm this correlation, previous studies confirm these results and suggest that cover sagging, or cover suffusion sinkholes may represent a very large group of sinkholes traditionally unaccounted for in current sinkhole assessment maps in Florida. The methodology presented in this study can be easily extrapolated to other areas to further expand current sinkhole hazard and distribution maps.
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Date Issued: 2021
PURL: http://purl.flvc.org/fau/fd/FA00013872
Subject Headings: Sinkholes--Florida, Martin County (Fla.), Karst, Remote sensing
Format: Document (PDF)

Title: INVESTIGATING DEPRESSIONAL FEATURES ASSOCIATED WITH SINKHOLES IN DEEP-SEATED INTERSTRATAL KARST USING NEAR-SURFACE SEISMIC REFLECTION TECHNIQUES IN CENTRAL FLORIDA.
Creator: Khan, Haibat, Comas, Xavier, Florida Atlantic University, Department of Geosciences, Charles E. Schmidt College of Science
Abstract/Description: Sinkholes are one of the major geohazards in karst areas, causing significant economic damage and even occasional loss of life. Sinkhole formation mechanisms vary depending on geological conditions but are initiated by dissolution of bedrock (generally carbonates or evaporites) below the ground resulting in ground surface deformation and eventual collapse. The process may be accelerated by natural events like storms or heavy rains and droughts, or human activities like water pumping or...
Show moreSinkholes are one of the major geohazards in karst areas, causing significant economic damage and even occasional loss of life. Sinkhole formation mechanisms vary depending on geological conditions but are initiated by dissolution of bedrock (generally carbonates or evaporites) below the ground resulting in ground surface deformation and eventual collapse. The process may be accelerated by natural events like storms or heavy rains and droughts, or human activities like water pumping or loading of the land surface. In Florida, limestone dissolution leading to sinkhole development often results in the formation of surface depressions that are often water-filled and develop into depressional wetlands. Previous studies using near-surface geophysical imaging techniques (including seismic refraction) in Central Florida have shown the correspondence between depressional wetlands and sinkholes originated in deep-seated interstratal karst with a variable overburden. However, these geophysical techniques are often unable to reach the karst interface which may typically be positioned at depths exceeding < 50-60 m. This research investigates the use of ground-based seismic reflection techniques to image deep paleokarst relief and better understand sinkhole development and extent below the overburden. This approach follows earlier studies by others using seismic reflection methods to identify sinkholes under lakes in Central Florida. While these previous studies deployed the method over water, the approach here investigates how land-based near-surface seismic reflection surveys may provide similar results below depressional wetlands. A total of three different locations with depressional wetlands under similar geological conditions (but somewhat variable depth to the karst interface) are investigated, including the Disney Wilderness Preserve near Poinciana (FL), the Allapattah Flats Wildlife Management Area near Palm City (FL); and the J.W. Corbett Wildlife Management Area in Palm Beach County (FL).
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Date Issued: 2022
PURL: http://purl.flvc.org/fau/fd/FA00013957
Subject Headings: Sinkholes--Florida, Karst, Imaging systems in geophysics, Seismic reflection method
Format: Document (PDF)

Title: Estimating Belowground Carbon Stocks in Isolated Wetlands of the Northern Everglades Watershed, Central Florida, Using Ground Penetrating Radar and Aerial Imagery.
Creator: McClellan, Matthew, Comas, Xavier, Benscoter, Brian, Hinkle, Ross, Sumner, David
Date Issued: 2017-11-06
PURL: http://purl.flvc.org/fau/flvc_fau_islandoraimporter_10.1002_2016JG003573_1632253498
Format: Citation

Title: Use of Ground Penetrating Radar (GPR) in a Study on Beach Morphodynamics at Red Reef Beach, Boca Raton, Florida.
Creator: Camara dos Santos Porto, Sabrina, Briggs, Tiffany Roberts, Comas, Xavier, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Geosciences
Abstract/Description: The internal architecture of a beach system can provide clues into the processes involved in its formation, including depositional processes, and/or driving mechanisms (Billy et al., 2014). Several unique events such as cold fronts or Hurricane Irma caused conditions that resulted in erosion and accretion changes in Red Reef Beach - Boca Raton, throughout the year of 2017. Since the lateral extent of these changes is difficult to evaluate using traditional methods such as coring, a Ground...
Show moreThe internal architecture of a beach system can provide clues into the processes involved in its formation, including depositional processes, and/or driving mechanisms (Billy et al., 2014). Several unique events such as cold fronts or Hurricane Irma caused conditions that resulted in erosion and accretion changes in Red Reef Beach - Boca Raton, throughout the year of 2017. Since the lateral extent of these changes is difficult to evaluate using traditional methods such as coring, a Ground Penetrating Radar (GPR) was tested, which allows for a good lateral resolution (cm scale), to image the distribution and evolution of these sediments. The objectives of this study were to 1) explore the lateral variability in the internal architecture of sediments in Red Reef beach in Boca Raton (FL) using an array of ground penetrating radar (GPR) measurements constrained with coring and sediment analysis; 2) explore how dynamics of erosion and accretion induced by changes in wave activity and related to tide variation and storm events, may affect surface topography and the sedimentary internal architecture of beach deposits, using RTK GPS and GPR time-lapse measurements; 3) to explore changes in the lateral extent of the freshsaltwater interface along the beach profile in relation to tide variation and storm events. Reflectors identified in the GPR images showed some evidence of erosional and accretionary surfaces preserved in Red Reef beach. These measurements were repeated over time coinciding with certain events (such as Hurricane Irma) to explore their effects in terms of sediment erosion and accretion as reflected in changes in topography (using time-lapse GPS-RTK measurements), and changes in the internal sedimentary architecture (using time-lapse GPR measurements). The datasets collected also revealed the temporal evolution of the salt-freshwater interface, showing how the lateral extent of saltwater saturated sediment (inferred from areas of GPR signal attenuation along the profiles) evolved over time. This study shows the potential of GPR to provide information about beach sediment processes and dynamics at resolutions beyond traditional measurements (such as coring). It also shows the importance of combining methods that are complementary, such as the use of RTK GPS to explore changes in topography, and GPR that provides information on subsurface sedimentary architecture and the mechanism of change such as post-storm recovery. This study has implications for better understanding changes in coastal sedimentary deposits and processes, both at the subsurface, particularly after high-energy events, such as hurricanes, that result in rapid changes in erosion and/or accretion of sediments.
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Date Issued: 2017
PURL: http://purl.flvc.org/fau/fd/FA00005947
Subject Headings: Dissertations, Academic -- Florida Atlantic University, Beaches--Florida, Ground penetrating radar., Sediments (Geology)--Analysis.
Format: Document (PDF)

Title: Using Hydrogeophysical Methods for Investigating Carbon Dynamics in the Greater Everglades Watershed: Implications for the Spatial and Temporal Variability in Carbon Stocks and Biogenic Gas Fluxes.
Creator: McClellan, Matthew D., Comas, Xavier, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Geosciences
Abstract/Description: Peat soils store a large fraction of the global soil carbon (C) pool and comprise 95% of wetland C stocks. They also have the capability to produce and release significant amounts of greenhouse gasses (CO2, CH4) into the atmosphere. Most studies of wetland soil C and gas flux dynamics have been done in expansive peatlands in northern boreal and subarctic biomes. However, wetlands in temperate and tropical climates are vastly understudied despite accounting for more than 20% of the global...
Show morePeat soils store a large fraction of the global soil carbon (C) pool and comprise 95% of wetland C stocks. They also have the capability to produce and release significant amounts of greenhouse gasses (CO2, CH4) into the atmosphere. Most studies of wetland soil C and gas flux dynamics have been done in expansive peatlands in northern boreal and subarctic biomes. However, wetlands in temperate and tropical climates are vastly understudied despite accounting for more than 20% of the global peatland C stock and storing large amounts of biogenic gasses Although studies investigating greenhouse gas dynamics from peatlands have increased during the last decade, the spatial and temporal distribution of these gases still remains highly uncertain, mainly due to the limitations in terms of spatial and temporal resolution and invasive nature of most methods traditionally used. This thesis combines a series of field and laboratory studies at several sites in the Greater Everglades as examples to show the potential of hydrogeophysical methods to better understand: 1) the belowground C distribution and overall contribution to the global C stocks of certain wetlands (Chapter 2); and 2) the spatial and temporal variability in both C accumulation and releases from peat soil monoliths from several wetland sites in the Greater Everglades (Chapter 3 and 4). To estimate belowground C in the field, I used a combination of indirect non-invasive geophysical methods (GPR), aerial imagery, and direct measurements (coring) to estimate the contribution of subtropical depressional wetlands to the total C stock of pine flatwoods landscape at the Disney Wilderness Preserve (DWP, Orlando, FL). Three-dimensional (3D) GPR surveys were used to define the thickness of stratigraphic layers from the wetland surface to the mineral soil interface within depressional wetlands. Depth-profile cores in conjunction with C core analysis were utilized to visually confirm depths of each interface and estimate changes in soil C content with depth and were ultimately used to estimate total peat volume and C stock for each depressional wetland. Aerial photographs were used to develop a relationship between surface area and total wetland C stock, that were applied to estimate total landscape C stock of all depressional wetlands throughout the entire preserve. Additionally, low-frequency GPR surveys were conducted to image the stratigraphy underneath the peat basin of depressional wetlands to depict lithological controls on the formational processes of depressional wetlands at the DWP. Spatial and temporal variability in biogenic greenhouse gas (i.e. methane and carbon dioxide) production and release were investigated at the laboratory scale. Two 38 liter (0.5 m x 0.23 m x 0.3 m) peat monoliths from two different wetland ecosystems in central Florida (sawgrass peatland and a wet prairie) were compared in order to understand whether changes in matrix properties influence gas dynamics in a controlled environment (i.e. constant temperature). Gas content variability (i.e. build-up and release) within the peat matrix was estimated using a series of high frequency (1.2 GHz) GPR transects along each sample about three times a week. An array of gas traps (eight per sample) fitted with time-lapse cameras were also used in order to constrain GPR measurements and capture gas releases at 15-minute intervals. Gas chromatography was performed on gas samples extracted from the traps to determine CH4 and CO2 content. Also, at the lab scale, temporal variability in biogenic gas accumulation and release was investigated in 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 GPR transects along the sample. This system ran virtually nonstop using high frequency (1.2 GHz) antennas. GPR measurements were again constrained with an array of gas traps (6) fitted with time-lapse cameras and gas chromatography. The aim of this study is to better constrain temporal scale, and better understand the heterogeneous nature (both in time and space) of gas releases from peat soils.
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Date Issued: 2019
PURL: http://purl.flvc.org/fau/fd/FA00013238
Subject Headings: Greenhouse gases, Everglades (Fla.), Peatlands, Carbon, Bogenic gas
Format: Document (PDF)

Title: Mapping the Fresh-Saltwater Transition Zone Across the Beach Environment Using Ground-Penetrating Radar (GPR).
Creator: Becker, Joseph Michael, Roberts Briggs, Tiffany, Comas, Xavier, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Geosciences
Abstract/Description: As sea level rises, saltwater migration can threaten coastal ecosystems and beach-dune environments, which negatively impacts coastal flora. This study uses ground penetrating radar (GPR) to evaluate the spatiotemporal variability of saltwater migration in the near shore at high lateral resolution (i.e. cm) by using daily micro tidal cycles as analogs to infer saltwater migration. Time-lapse GPR profiles were collected at low and high tide capturing phase lags of the tidal flux through...
Show moreAs sea level rises, saltwater migration can threaten coastal ecosystems and beach-dune environments, which negatively impacts coastal flora. This study uses ground penetrating radar (GPR) to evaluate the spatiotemporal variability of saltwater migration in the near shore at high lateral resolution (i.e. cm) by using daily micro tidal cycles as analogs to infer saltwater migration. Time-lapse GPR profiles were collected at low and high tide capturing phase lags of the tidal flux through different substrates. GPR measurements were collected at two sites in Miami with contrasting lithologies: a) Crandon Park, composed of unconsolidated sand; and b) the Barnacle Historic State Park, composed of the Miami Limestone Formation. Laboratory-scale GPR measurements were collected over samples mimicking field conditions. The results may be helpful to identify regions vulnerable to saltwater migration in the near shore based on lithological variability, and to mitigate negative impacts for flora in beach-dune habitats during sea level rise.
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Date Issued: 2019
PURL: http://purl.flvc.org/fau/fd/FA00013183
Subject Headings: Ground penetrating radar, Saltwaters, Seashore ecology, Coastal ecology
Format: Document (PDF)

Title: FAU Climate Change Initiative Priority Theme: Research, Engineering, and Adaption to a Change Climate.
Creator: Berry, Leonard, Koch, Marguerite, Center for Environmental Studies, Benscoter, Brian, Comas, Xavier, Devlin, Donna, Fadiman, Maria, Gerstein, E., Herzing, Denise L., Hindle, Tobin, Milton, Sarah L., Oleinik, Anton E., Proffitt, C. Edward, Restrepo, Jorge I., Root, Tara L., Wyneken, Jeanette, Xie, Zhixiao, Zhang, Xing-Hai, Esnard, Ann-Margaret, Mitsova, Diana, Murley, J., Vos, J., Escaleras, Monica, Mehallis, M., Shaw, Eric H., Hardman, Guillermo [John], Lambert, Julie, Thomas, G., Arockiasamy, Madasamy, Bloetscher, Frederick, Carvalho, G., Dhanak, Manhar R., Frisk, George V., Kaisar, Evangelos I., Kalva, Hari, Meeroff, Daniel E., Rodriguez, Jarice, Scarlatos, Panagiotis (Pete) D., Shankar, Ravi, Teegavarapu, Ramesh, Brown, Clifford T., McAfee, Francis, Widener, Patricia, Dalgleish, Fraser R., Hanisak, M. Dennis, McMulloch, S., O'Corry-Crowe, Gregory, Pomponi, Shirley A., Reed, John K., Scarpa, John, Voss, Joshua, Heimlich, Barry N., Alvarez, R., Jolley, J., Edwards, A., Charles E. Schmidt College of Science, Harbor Branch Oceanographic Institute, College of Business, Dorothy F. Schmidt College of Arts and Letters, College of Education, College of Engineering and Computer Science
Date Issued: 2010
PURL: http://purl.flvc.org/fau/fd/FA00003457
Format: Citation

FAU Theses and Dissertations (11)	+ -
FAU College Collections (5)	+ -
FAU Undergraduate Student Research (2)	+ -

Peatlands (4)	+ -
Biogenic gas (3)	+ -
Peat soils (3)	+ -
Everglades (Fla) (2)	+ -
Everglades (Fla.) (2)	+ -

Gas dynamics (2)	+ -
Greenhouse gases (2)	+ -
Ground penetrating radar (2)	+ -
Karst (2)	+ -
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Big Cypress National Preserve (Fla.) (1)	+ -
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Everglades National Park (Fla.) -- Environmental conditions (1)	+ -
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Ground penetrating radar. (1)	+ -
Imaging systems in geophysics (1)	+ -
Limestone -- Florida -- Miami Dade County -- Analysis (1)	+ -
Martin County (Fla.) (1)	+ -

Electronic Thesis or Dissertation (11)	+ -
article (4)	+ -
poster (2)	+ -
report (1)	+ -

Comas, Xavier (18)	+ -
Charles E. Schmidt College of Science (12)	+ -
Department of Geosciences (11)	+ -
Florida Atlantic University (11)	+ -
Benscoter, Brian (2)	+ -

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