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