eddy covariance measurements of co and ch4 with a view to ......eddy covariance measurements of co 2...
TRANSCRIPT
Eddy Covariance Measurements of CO2 and
CH4 with a view to Optimizing Carbon Capture
in Wetland Restoration
Grant. C Edwards, N. Saintilan, K. Negandhi, K. Tewari
Macquarie University, Faculty of Science and Engineering, Department of Environmental Sciences, Sydney, NSW, Australia
Goals and Motivations
• The artificial isolation of floodplain wetlands from inundation has been one of the most
widespread causes of ecological decline across the globe.
• Wetlands are biodiversity hotspots in the landscape, and their isolation from floodwaters
and, on the coast, flood tide inundation has led to the degradation of ecological services
including reductions in fisheries production, waterbird habitat, and habitat refugia.
• Scientific and policy interest has recently turned to the value of coastal wetlands for
carbon sequestration (“Blue Carbon”).
• Coastal mangrove and saltmarsh restorations are now at the forefront of developments
for ecosystem-based climate change mitigation and adaptation.
• The 2013 (Wetlands Supplement) to the 2006 IPCC Guidelines for National Greenhouse
Gas Inventories provides a framework for the incorporation of wetland carbon
sequestration in national carbon accounts.
Goals and Motivations
• Tomago wetland located near Newcastle, NSW,
Australia is undergoing rehabilitation restoring tidal
inundation to a previously leveed floodplain
• It is hypothesised that the restoration of tidal
inundation would convert a methane source into a
sink as a consequence of soil salinization.
• A Before-After-Control-Impact experimental
design has been applied to measure the impact of
tidal reinstatement on wetland floodplain accretion
and gas flux.
Tomago
Methodology
• 4 months prior to tidal reinstatement, we have installed
an extensive set of environmental measurements at
impacted and control sites.
• Hydrodynamic modelling identified the sites within the
wetland predicted to remain disconnected from tidal flow.
• Eddy covariance tower at disturbed site, Gill Windmaster,
LICOR 7500,7700 open path (CO2, CH4, H2O).
• LICOR smart flux system, eddypro software, QA/QC
procedures, telemetry
• 4 component radiation (Kipp and Zonen cnr1), soil surface
temperature (thermocouple). 4
Methodology
5
• Electron conductivity and water temperature (HOBO® U24)
• RSET-MH: Surface elevation, surface accretion, and
continuous water level (HOBO U20L) inundation regime.
• Soil microbial community sampling and analysis (16S rRNA
gene milliseq).
• Local Air samples for carbon isotopes of CO2 and CH4
including hydrogen isotopes for methane.
• Meteorological data from nearby (10 Km) Williams Town
air base including precipitation
• Soil sampling, vegetation surveys
Methodology
6Faculty of Science and Engineering
Methodology
Methodology
Methodology
Methodology
Methodology
Results
• Eddy covariance measurements began August 4, 2015
and is ongoing.
• Tidal re-instatement was mid November 2015.
• Presented are preliminary results from August 2015
to May 2016.
12
-0.4
-0.2
0.0
0.2
0.4
0.6
Aug Sept Oct Nov Dec Jan Feb March April May
Flu
x (
g m
-2 h
-1)
CO2
Results
0
5
10
15
20
25
30
0
50
100
150
200
250
300
350
400
450
Aug Sept Oct Nov Dec Jan Feb March Apil May
Tem
p (
C)
Rai
nfa
ll (m
m)
Rainfall (mm) Temperature (C)
-2
-1
0
1
2
Aug Sept Oct Nov Dec Jan Feb March April May
Flu
x (m
g m
-2 h
-1)
CH4
0
5
10
15
20
25
30
35
0
100
200
300
400
500
Aug Sept Oct Nov Dec Jan Feb March Apil May
Co
nd
uct
ivit
y (m
scm
-1)
Rai
nfa
ll (m
m)
Rainfall (mm) Conductivity
Results
• William Town climatology:
60 yr. record of rainfall and
temperature1942 to 2002
• Study period to date anomalous
with respect to precipitation
input
Results: monthly and seasonal
-0.2
0.0
0.2
0.4
Sept, Oct, Nov Dec, Jan, Feb March, Apr,May
June, July, Aug
Flu
x (g
m-2
h-1
)
CO2
-1.0
-0.5
0.0
0.5
1.0
Sept, Oct, Nov Dec, Jan, Feb March, Apr,May
June, July, Aug
Flu
x (m
g m
-2 h
-1)
CH4
-0.4
0.0
0.4
0.8
Aug Sept Oct Nov Dec Jan Feb March April May
Flu
x (g
m-2
h-1
)
CO2
-6
-4
-2
0
2
4
6
Aug Sept Oct Nov Dec Jan Feb March April May
Flu
x (m
g m
-2 h
-1)
CH4
Results: Before and After Flooding
-0.2
0.0
0.2
0.4
Before (Aug-Oct) After (Dec-May)
Flu
x (g
m-2
h-1
)
CO2
-0.4
0.0
0.4
0.8
Aug Sept Oct Nov Dec Jan Feb March April May
Flu
x (g
m-2
h-1
)
CO2
-6
-4
-2
0
2
4
6
Aug Sept Oct Nov Dec Jan Feb March April May
Flu
x (m
g m
-2 h
-1)
CH4
-0.6
-0.3
0.0
0.3
0.6
Before (Aug-Oct) After (Dec-May)
Flu
x (m
g m
-2h
-1) CH4
Results: Comparison
CO2(g m-2 h-1)
CH4(g m-2 h-1)
Before -0.0850 0.000113
After 0.116 -0.0000734
Sum (NOT including Nov when
flooding occurred and we have no CH4 data)
0.374 -0.0000221
Wetlands GWP after flooding (after Nov)
CO2
(g m-2 h-1)CH4 expressed
as CO2
(g m-2 h-1)
SUM
100 yr GWP (CH4 x 21)
0.1163 -0.00154 0.1148
20 yr GWP(CH4 x 31)
0.1163 -0.00227 0.1140
• To date we are not seeing a clear
signal from tidal re-enstatement,
especially for methane.
• Averaging CO2 before and after
tidal re-instatement does show,
coincidently, a change from a
sink to a source.
• Over the ten months of
measurements methane is a
small source to the atmosphere.
• CO2 is the dominate source of
carbon to the atmosphere.
y = -44.121x + 485.88R² = 0.9991
-1.2E+05
-1.1E+05
-1.0E+05
-9.0E+04
-8.0E+04
-7.0E+04
-6.0E+04
1700 1900 2100 2300 2500 2700
pp
b *
δ1
3 C(p
pb
‰)
CH4 (ppb)
Dec
y = -57.585x + 23998R² = 0.7059
-8.6E+04
-8.4E+04
-8.2E+04
-8.0E+04
-7.8E+04
-7.6E+04
1750 1800 1850 1900
pp
b *
δ1
3 C (
pp
b ‰
)
CH4 (ppb)
Sept
• December– Wind direction: 68° to 85°
– Input signature: -44.1
• Thermogenic/fossil fuel
• September– Wind direction: 140° to 204°
– Input signature: -57.6
• Biogenic input signature
Results: Air sampling CH4 stable isotope signatures
• δ13C signatures of CH4 indicate carbon source (Whiticar 1999)
– Biogenic δ13C < -50
– Thermogenic/fossil fuel δ13C > -50
Results: atmospheric isotopic sampling
y = -67.09x + 41973R² = 0.85828
-8.6E+04
-8.4E+04
-8.2E+04
-8.0E+04
-7.8E+04
-7.6E+04
1750 1800 1850 1900
pp
b *
δ1
3 C (
pp
b ‰
)
CH4 (ppb)
26 Sept
y = -74.849x + 54080R² = 0.9673
-8.6E+04
-8.4E+04
-8.2E+04
-8.0E+04
-7.8E+04
1780 1800 1820 1840 1860
pp
b *
δ1
3 C (
pp
b ‰
)
CH4 (ppb)
27 Sept
y = -57.585x + 23998R² = 0.7059
-8.6E+04
-8.4E+04
-8.2E+04
-8.0E+04
-7.8E+04
-7.6E+04
1760 1780 1800 1820 1840 1860 1880 1900
pp
b *
δ1
3C
(p
pb
‰)
CH4 (ppb)
SeptWind: 140° to 170°Input signature: -67.1
Wind: 190° to 204°Input signature: -74.9
CH4 (ppm)
Results: December
CO2 ppm (x100)
CH4 (ppm)
Results: September
CO2 ppm (x100)
Conclusions
22Faculty of Science and Engineering
• Tidal re-instatement in impounded wetlands potentially represents and important
“blue carbon” opportunity in Australia
• Tidal re-instatement does not prevent periodic freshening and associated
greenhouse gas production.
• In the first 10 months carbon budget dominated by freshwater inputs as opposed to signal
from tidal re-instatement
• Site may be influenced by anthropogenic atmospheric input to background air (military base)
• As complete data set is collected/analysed and integrated to describe the carbon budget at this
site the full impact of restoration is unknown.
Acknowledgements
23Faculty of Science and Engineering
• NSW Office of Environment and Heritage
(funding, field support)
• Professor Martin Kennedy
(loan of EC tower, postdoc)
• KerryLee Rogers and Chris Owers,
University of Wollongong
• Will Glamore, Water Research Laboratory