Peatlands are large terrestrial storages for carbon (C) and sources of greenhouse gases such as methane (CH4) and carbon dioxide (CO2). Although many studies over the last two decades have focused on estimating carbon fluxes from peatlands (particularly in boreal systems), the temporal and spatial distribution of biogenic gases within the peat soil is still not well understood. Furthermore, most of these previous studies were conducted in high-latitude peatlands, while recent research suggests that gas production and emission rates from low-latitude peatlands in areas such as the Everglades may be larger than what was previously thought. The research presented here investigates the spatial and temporal variability of gas dynamics in low-latitude peatlands at the field scale (1-10m). This study was conducted in the landscape scale Loxahatchee Impoundment Landscape Assessment (LILA), an 80 acre, hydrologically controlled model containing the four different environments found in the 1.7 million acre Everglades. Here we used a 2-D grid of GPR transects in conjunction with gas chambers monitored with time-lapse photography and surface deformation measurements to monitor gas accumulation and release over an approximate 100 m² area. This work has implications for better estimating carbon fluxes from peat soils in the Everglades, and highlights the spatial and temporal heterogeneity of gas dynamics.

1. 00
Utilizing Ground Penetrating Radar (GPR) to Investigate the
Temporal and Spatial Distribution of Biogenic Gases from Peat Soils
at the Loxahatchee Impoundment Landscape Assessment (LILA)
Thomas A. Shahan, Nathaniel Sharp, Willliam Wright, and Xavier Comas
Department of Geosciences, Florida Atlantic University
Peatlands are large terrestrial storages for carbon (C) and sources of greenhouse gases
such as methane (CH4) and carbon dioxide (CO2). Although many studies over the last
two decades have focused on estimating carbon fluxes from peatlands (particularly in
boreal systems), the temporal and spatial distribution of biogenic gases within the peat
soil is still not well understood. Furthermore, most of these previous studies were
conducted in high-latitude peatlands, while recent research suggests that gas production
and emission rates from low-latitude peatlands in areas such as the Everglades may be
larger than what was previously thought. The research presented here investigates the
spatial and temporal variability of gas dynamics in low-latitude peatlands at the field
scale (1-10m). This study was conducted in the landscape scale Loxahatchee
Impoundment Landscape Assessment (LILA), an 80 acre, hydrologically controlled model
containing the four different environments found in the 1.7 million acre Everglades. Here
we used a 2-D grid of GPR transects in conjunction with gas chambers monitored with
time-lapse photography and surface deformation measurements to monitor gas
accumulation and release over an approximate 100 m² area. This work has implications
for better estimating carbon fluxes from peat soils in the Everglades, and highlights the
spatial and temporal heterogeneity of gas dynamics.
Intro
Field Site/Experiment Setup
Gas Traps Deformation Rod
Methods
Time lapse camera
160 MHz GPR
Raft
Results
Line1
Line10
Line9
Line8
Line7
Line6
Line5
Line4
Line3
Line2
X -axis
Y-axis
Gas Traps
N
1m
Time(ns)
Distance (Meter)
Depth(Meter)atv=0.03(m/ns)
0
20
40
60
80
100
1 2 3 4 5 6 7 8
0
0.5
1.0
1.5
antennas
Tx Rx
Ground Penetrating Radar (GPR)
References Acknowledgements
Wright, William J. "Investigating Variability of Biogenic Gas Dynamics in Peat Soils
using High Temporal Frequency Hydrogeophysical Methods." ProQuest, UMI
Dissertations Publishing, 2013.
This work was partially supported by NOAA (grant # GC11-337), and South Florida
Water Management District, We thank Arthur R. Marshall Loxahatchee National
Wildlife Refuge for allowing us access and permission for research. We also thank
Eric Cline with the South Florida Water Management District.
- Gas content distribution in the peat soils of the Everglades are highly variable spatially; i.e. range between 4-16 % gas content within a 10m x 9m
grid.
-Comparison of area details within the 2-d gas content contour plots (arrows X and Y in fig.2) highlight heterogeneity of gas dynamics at the plot
scale.
-Overall averages of gas content measured with GPR, compared with Average flux from gas traps (fig.1b) suggests that gas flux increases with gas
content.
-General trends of build up and release show an overall increase in gas content and flux release potentially related to certain environmental variables
such as temperature.
1) Temporal Variability
Summary
2) Spatial Variability
1.5 mgCH4/m2/d 2.5 mgCH4/m2/d02/13/15
Percent gas content on a field scale
EA1
EB1
EA2
EB2
EA3
EB3
WA1
WB1
WA2
WB2
WA3
WB3
2.2 mgCH4/m2/d
8
02/02/15 1.2 mgCH4/m2/d02/19/15
19.5 mgCH4/m2/d03/05/15
02/09/15
Average percent gas content zoomed in:
b)
a)
missing data
2m
3m
02/09/15
12.2% avg gas
content 2m
3m
02/13/15
12.0% avg
gas content
2m
3m
02/19/15
11.9% avg
gas content
X
2m
3m
02/09/15
Y
13.4% avg
gas content
14.0%
avg gas
content
5.7 mgCH4/m2/d
2m
3m
02/13/15
9.7%16.8 mgCH4/m2/d
2m 3m
02/19/15
9.3%
10.2% avg
gas content
3.9 mgCH4/m2/d
10m
9m
33 mgCH4/m2/d03/12/15 69.4 mgCH4/m2/d03/19/15
Y
X
GPR Gas Content
16
14
12
10
8
6
4
GPRGasContent
8.9% avg
gas content
1.57 mgCH4/m2/d 1.63 mgCH4/m2/d 2.1 mgCH4/m2/d