8/4/2010
The Dissolved Organic Carbon
content of headhead-water streams in
forested catchments.
Why Carbon in Water?
Intensive research on the importance of carbon in:
•Atmospheric Emissions;
•Forest and ocean stores; and
•The Atmospheric flux
There has been limited research on carbon and
terrestrial hydrology
Honours Project - Ian Riley
Supervisors
- Dr John Gibson (TAFI)
- Dr Sandra Roberts (FT)
- Dr Mark Hovenden (UTas)
Dissolved Organic Carbon (DOC) has the potential
to be an important link between terrestrial, aquatic
2
and atmospheric stores
Study Objectives
What is DOC
• Organic carbon that will pass through a
0.45 micron filter.
• Measure temporal and spatial variation of
DOC in head – water streams of forested
catchments.
• A reliable quantitative measure of the
many simple and complex organic
molecules that exist.
• Investigate correlations between DOC,
Flow, Temperature, Turbidity and Electrical
Conductivity (EC)
• Derived from aquatic or terrestrial sources.
3
• Assess DOC composition to understand
the source.
4
Sample Collection Process
• Simultaneous periodic grab samples
– Fortnightly diurnal sampling of each creek
(1.5hr Warra- 3 hr Swanson & King)
• 48 hr sampling event (Diurnal/Nocturnal)
– Regular 2hr samples over a 48hr period (Warra)
• In-situ analysis - water quality parameters
– Flow, Temperature, Electrical Conductivity (EC) and
Turbidity.
5
6
1
8/4/2010
Results
DOC Analysis
Is expensive and time consuming!
Concentration of DOC (mgL-1)
Employed 3 techniques
Warra
– Direct combustion method (ALS)
8.7
8.8
8.2
(Aug-Feb)
(5.7-13.3)
(5.5-13.4)
(6.2-10.7)
• UV- Visible spectrum (200-700nm) at 2.5nm
intervals
– Fluorescence
Cooler Months
8.8
9.1
8.3
(Aug-Oct)
(7.2-10.4)
(7.2-10.5)
(6.7-9.9)
Warmer Months
8.6
8.6
8.1
(Nov-Feb)
(5.7-13.3)
(5.5-13.4)
(6.2-10.7)
7
8
Temporal & Spatial Variation between
and within creeks
Proxy Measure for DOC
AAB
14
BAC
12
AAA
CAB
BAB
10
DOC (mgL-1)
King
Total Sample Period
– Spectrographic analysis
• Excitation/Emission Matrices
Swanson
ABC
BBA
8
ACB
ACB
6.01.10
20.1.10
6
4
2
0
23.09.10
Warra
7.10.09
28.10.09
Swanson
King
11.11.09
26.11.09
9.12.09
23.12.09
Sample Events
• Frequent DOC analysis is expensive in
both time and money.
• Frequent sampling is required to get an
accurate measure.
• Investigated potential correlations with
common water quality parameters to find
predictors of DOC.
• Flow, Temperature, Turbidity and EC
9
10
Warra Creek - Temperature vs DOC
Warra Creek - Flow vs DOC
14
16
R² = 0.89
14
12
R² = 0.92
10
DOC (mgL-1)
DOC (mgL-1)
12
10
8
R² = 0.68
6
8
R² = 0.43
6
4
4
2
2
0
0
0
100
200
300
400
500
600
700
Flow Rate (ms-1)
Cooler Months
Warmer Months
0
2
4
6
8
10
12
14
Temperature (0C)
11
Cooler Months
Warmer Months
12
2
8/4/2010
Warra Creek - EC vs DOC
Warra Creek - Turbidity
14
16
14
12
R² = 0.00
R² = 0.01
R² = 0.51
10
DOC (mgL-1)
DOC (mgL-1)
12
10
8
6
8
R² = 0.40
6
4
4
2
2
0
0
0
20
40
60
80
100
120
140
0
10
20
Turbidity (NTU)
Cooler Months
Warmer Months
30
40
EC (uScm-1)
Cooler Months
13
50
60
Warmer Months
14
Predicting DOC using Model
Further Analysis
R2
1
0.05 - 0.19
2
0.11 - 0.28
3
0.21 - 0.31
4
0.32
4 (Season)
0.58 - 0.72
4 (Site)
0.60-0.79
4 (Season & Site)
0.92 – 0.99
Flow Rate (L s-1)
# Factor
1400
40
1200
35
30
1000
25
800
20
600
15
400
10
200
0
20/08/2009
5
30/08/2009
9/09/2009
Average Daily Flow
15
How does this compare ?
DOC (mg L-1)
Warra Creek Aug 20th-Sept 30th
Multiple Linear Regression
19/09/2009
0
29/09/2009
Average Daily DOC
Warra - Sept 2009 = 5650 kg C Warra - 20th Aug- 31st Aug =8280 kg C
16
How does this compare ?
• If September is a representative month of the year
67.8 tCyr-1
• Allowing for 4 high flow events similar to the one
seen in August this will increase to 93.4 tCyr-1
• Warra Creek Catchment is 462ha, therefore
• 200 kgCha-1yr-1 exported from Warra Creek
Catchment
• Land afforested with Norway spruce in Sweden
250-310 kgCha-1yr-1
• British Rivers surrounds by Peatlands
7.7-103.5 kgCha-1yr-1
• One example in boreal forests up to
433 kgCha-1yr-1
On average 200 kgCha-1yr-1 is exported from the
Warra Creek Catchment
17
18
3
8/4/2010
DOC Composition
What does this mean?
• Derived from aquatic or terrestrial Sources.
• In terms of Australian forests
– Above ground carbon estimates are between
260-2500 tCha-1
– On average an established an Australian forest
sequesters 2.4 t C ha-1yr-1 (depending on age
and forest type)
– Carbon lost through DOC Export 0.2 t C ha-1yr-1
– Established forests may be losing up to 8% of
the annual carbon sequestered through DOC
runoff.
• Fluorescence Excitation Emission Matrix
and UV –Vis spectral slope to determine
dominant source.
• The carbon of all three Creeks was
predominantly terrestrial with minimal
aquatic contribution.
19
20
Implications
Summary
• DOC concentration
– Varies through time and space
– It is a function of flow and supply
• DOC can be predicted
– From easily measured parameters
– Most powerful when spatial and seasonal
variation is taken into account.
• Composition
– The DOC in Warra, Swanson and King creek is
predominantly terrestrially derived.
If our method of analysis and assessment is
implemented:
− DOC can be predicted using easily measured
parameters. This knowledge can be used in
long term forest carbon assessment.
− Riverine carbon export can be a consideration in
Water quality and forest management.
− Can provide a base line for climate change
research, enabling impact assessments,
modeling and mitigation.
21
Further Study
22
Acknowledgements
• Expand over the entire year and across
varied sites.
• The influence of soil water resident time
and time since last flood event.
• Detailed assessment of the chemical
composition of DOC, and determining
various sources.
• Assessment of the effects of land
management on DOC.
John Gibson - IMAS/TAFI
Sandra Roberts - FT
Mark Hovendon - UTAS
Neil Davidson, Brad Potts (Utas), Tim Wardlaw (FT) and
the CRC for Forestry and Forestry Tasmania - Project
Inception and Funding.
Philip Smethurst (CSIRO), Kevin Petrone (CSIRO) & Jason Fellman
(UWA) - Fluorescence Analysis
Greg Jorden – Environmental Design
Jaz Janes, Erin Trainer, Jodi Noble – General Project Support
23
Meg Riley, Imojen Riley, Pete Walsh, Kate Evans, Sam Woods –
Mental and Emotional Support
24
4
8/4/2010
Additional Information
Questions?
25
26
Fluorescence Excitation
Emission Matrix – Warra Creek
DOC Composition
• DOC is comprised of a mix of simple
and complex organic molecules:
• Aquatic Humic Substances
(Humic and Fulvic Acids 50-80%)
• Carboxylic Acids, Phenols & Tannins 5-8%
• Amino Acids 1-3%
• Carbohydrates 5-10%
• Hydrocarbons 1%
• Trace Compounds
27
Warra Creek
King Creek
A - Humic-like (Excitation 370-390nm/Emission 460-480nm)
B - Fulvic-like (Excitation 320nm-340nm/Emission 410-430nm)
C – Aquatic Protein-like (Excitation 275nm – Emission 350nm)
28
Swanson Creek
29
5