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Controls on organic matter degradability in suspended matter and sediments of the Elbe river (EGU2020-9015) F. Zander1, R.N.J. Comans2, A. Groengroeft3, A. Eschenbach3, T.J. Heimovaara1, J. Gebert1
1Delft University of Technology, Dept. Geoscience and Engineering, Stevinweg 1, 2628 CN Delft, The Netherlands 2Wageningen University and Research, Dept. Environmental Sciences, Droevendaalsesteeg 3, 6708 PB Wageningen, The Netherlands 3University of Hamburg, Dept. Department of Earth Sciences, Allende-Platz 2, 20146 Hamburg, Germany
Prediction of organic matter degradability in river sediments (EGU2020-22064) J. Gebert1, F. Zander1
1Delft University of Technology, Dept. Geoscience and Engineering, Stevinweg 1, 2628 CN Delft, The Netherlands
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Research questions
The described gradient of the organic matter degradability from upstream to downstream of the Elbe river (Zander et al. 2020) leads to the following questions:
• How does the organic matter quality vary along the upstream-downstream transect?
• How do the organic matter quality (origin and physicochemical properties) and sediment
properties influence the organic matter degradability?
• Can long-term degradation of sediment organic matter be inferred from short-term measurements?
Zander, F., Heimovaara, T., Gebert, J. (2020): Spatial variability of organic matter degradability in tidal Elbe sediments. Journal of Soils and Sediments. DOI https://doi.org/10.1007/s11368-020-02569-4.
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Investigation area: Port of Hamburg, Germany
HAMBURG
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Sampling locations, P1 to P9
Grey dots: focussed locations where DOC fractionation analyses were performed
Downstream, km 643
Upstream, km 616
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Sampling procedures
• 1 m core of the first sediment layers (7 to 17 m depth below water level)
• Stratified sampling of individual layers (see next slide)
• Sampling from March to November 1 x per month in 2018 and 2019
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A detailed look reveals...
• A multi-layered system, layers differ in – Flow behaviour (rheology) – Color (redox potential) – Density (in-situ) – Water content – C content and C
mineralisation – ... And many more
properties
• Consolidation chrono-sequence
• > 80% fines (< 63 μm) • FM = lutocline / “river
bottom”
Pre-consolidated sediment PS
Fluid mud FM
Oxidized or reduced
Reduced
Reduced
Consolidated sediment CS
Suspended particulate matter SPM, oxidized
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Methods
• Quantification of organic matter degradation and degradability – Long-term anaerobic incubations to quantify C mineralisation (> 250 d) – Organic matter pools (inferred from degradation rates)
• Selected properties of Elbe river water – Chlorophyll content
• Selected sediment properties – Biological parameters
• Extrapolymeric substances (EPS) • Microbial biomass
– Chemical parameters • DOC fractions (water and acid/base extractable) • Total DOC • Share of HoN, HA, Hi, and FA
– Physical parameters: • Density fractionation
• Correlation analyses – Influence of abiotic and biotic sediment properties on organic matter degradability
Time
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Controls on organic matter degradability in suspended matter and sediments of the Elbe river F. Zander1, R.N.J. Comans2, A. Groengroeft3, A. Eschenbach3, T.J. Heimovaara1, J. Gebert1
1Delft University of Technology, Dept. Geoscience and Engineering, Stevinweg 1, 2628 CN Delft, The Netherlands 2Wageningen University and Research, Dept. Environmental Sciences, Droevendaalsesteeg 3, 6708 PB Wageningen, The Netherlands 3University of Hamburg, Dept. Department of Earth Sciences, Allende-Platz 2, 20146 Hamburg, Germany
Ebullition of gas from anaerobic degradation of sediment organic matter in Port of Hamburg
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Water properties: chlorophyll concentration
• Chlorophyll gradient from upstream to downstream (measured in situ) – Small figure: multi-peak algae plume near location P8 (Hamburg Service portal, 2017-2020) – P0 (river-km 599) and P10 (river-km 646) are showing data from FGG server (Elbe data portal, 2020)
Hypothesis: Greater input of easily degradable organic matter (algae) at upstream locations (from P0)
P0 P1 P2 P8 P9 P100
20
40
60
80
100
120
140
160
Location
Chlo
roph
yll (
µg/l)
25%~75% Range within 1.5IQR Median Line Mean Outliers
210 µg/l
1-1-2017 1-1-2018 1-1-2019 1-1-2020
0
10
20
30
40
50
60
Chlo
roph
yll (
µg/l)
Time (Date)
2018 chlorophyll data
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Determination of organic matter pools • Organic matter pools are defined by OM degradation rate (k) / half life
• Prediction of gas generation with e.g. three phase function (y = A1*exp(-x/t1) + A2*exp(-x/t2) + A3*exp(-x/t3) + y0)
• Example for a three phase function – Total (assumed) gas generation: 14% TOC Exemplary cumulative C-degradation curve
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Determination of organic matter pools The borders between organic matter pools were chosen with respect to the overall range of organic matter decay rates (0.5 to 500 days): • Borders between pool one and pool two: half life of 5 days, corresponding degradation rate k: 0.06 • Between pool two and pool three: 50 days, corresponding degradation rate k: 0.006
k1 k2 k31E-4
0.001
0.01
0.1
1
Dec
ay ra
te
25%~75% Range within 1.5IQR Median Line Mean Outliers
• Half live of the anaerobic samples varied between 0.5 days and 500 days, corresponding decay rates varied between 0.6 and 0.0006
• Samples with greater decay rate than 0.06 belonged to pool 1 (k1)
• Samples with decay rate smaller than 0.006 days belonged to pool 3 (k3)
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Organic matter pools upstream vs. downstream • Anaerobic organic matter pools from June campaign 2018 • Upstream: more degradable OM and bigger pool 1 (fast degradable OM) • Downstream: mostly pool 3 (slow degradable OM) • N > 20
Downstream, km 643 Upstream, km 616
P1 P90
20
40
60
80
100
120
140
160
180
200
Ana
erob
ic p
ool s
izes
(mg
C/g
TO
C)
Pool 3 Pool 2 Pool 1
Hypothesis: easily degradable OM at upstream is degraded on its way downstream, this can show an age gradient and/or a source gradient. FM and PS only show pool 3 material – easily degradable material has been degraded.
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Anaerobic pool sizes with depth
16% 23%11% 8%
35%30%
33% 33%
49% 47%56% 59%
SPM FM PS CS0
20
40
60
80
100
Ana
erob
ic p
ool s
izes
(100
%)
Layer
P3 P2 P1
• Pool 1 is dominant at FM layers, pool 3 at CS layers. • Pool 2 is about one third of the total pool size • For each layer, around one half of have of the pool
size is made out of pool 3 • n > 50
Increasing depth
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Chemical organic matter fractionation
Methods
• Acid/base extraction • Water/CaCl2 extraction • Total DOC is separated into several fractions (e.g. humic acids, fulvic
acids, hydrophilic fraction, etc.)
• Here: focus on the hydrophilic DOC fraction (Hi)
For methods also see: Van Zomeren and Comans (2007), DOI https://doi.org/10.1021/es0709223
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Hydrophilic (Hi) DOC fraction (per DW / per TOC)
River-km 616
River-km 643
River-km 619 River-km 624
• Decreasing gradient from upstream to downstream • High Hi concentrations at areas with high OM degradation (high input of fresh OM) • High ratio between acid-base(AB)- and water-extraction at downstream due to low water
extractable Hi • Acid/base extraction is not/barely available for microbial organic matter degradation
Hypothesis: Hi is mostly responsible for the fast OM degradation and therefore an indicator for high OM quality at upstream locations
water extract per DW
PS CS FM PS CS PS CS PS CS0
1
2
Hy-
W (g
/kg
TOC
)
Layer (-)
Hy-W (g/kg TOC)
water extract per TOC
PS CS FM PS CS PS CS PS CS0.00
0.05
0.10
Hy-
W (g
/kg
DW
)
Layer (-)
Hy-W (g/kg DW)
Ratio AB-water
PS CS FM PS CS PS CS PS CS0
50
100
150
200
Hy
ratio
aci
d-ba
se to
wat
er (-
)
Layer (-)
Hy ratio acid-base to water (-)
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Hi fraction vs. anaerobic OM-pools, PS layers, 2018
• Fast and moderate degradable organic matter pools (pool 1 and pool 2) are correlating well with hydrophilic DOC fraction
• Slow degradable pool 3 is not correlating with Hi fraction
Hypothesis: pool 3 is not influenced by the Hi fraction. Pool 1 and pool 2 are driven by easily degradable OM, e.g. Hi fraction
0.00 0.02 0.04 0.06 0.08 0.100
20
40
60
80
100
120
140
160
180
G-pool 1 G-pool 2 G-pool 3 Linear fit pool1, Pearson: 0.76 Linear fit pool2, Pearson: 0.89 Linear fit pool3, Pearson: -0.18
Ana
erob
ic-T
OC
(mg
C/g
TO
C)
Hi (g/kg DW)
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Silicic acid, biomass, respiration activity (AT3h), EPS, PS layers, 2018+2019
• Downstream: lowest total amount of
biomass, anaerobic OM degradation after 100 days (G100) silicic acid and oxygen consumption after three hours (AT3h, lab value)
• Sample n between six and 18 Hypothesis: upstream is found more silicic acid, produced by algae, and more EPS, due to microbial activity, both resulting in a higher oxygen consumption, higher organic matter degradation and bigger pool 1 (not shown)
P0 P1 P2 P8 P9 P10
0
10
20
30
40
50
P1 P2 P80
2000
4000
6000
8000
10000
P0 P1 P2 P8 P9 P10-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
P0 P1 P2 P8 P9 P100
20
40
60
80
100
Silic
ic a
cid
(mg/
l)
Location
25%~75% 5%~95% Median Line Mean M
icro
bial
bio
mas
s (m
g/kg
DW
)
Location
AT 3
h g
O2/
g DW
)
Location
EPS
(mg/
g DW
)
Location
225 mg/g DW)
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Density fractionation: light organic matter fraction, 2019
• Upstream sediments contain higher concentrations of easily degradable organic matter per dry weight (left graph)
– Association of OM with mineral phase at downstream locations • Correlation hydrophilic DOC fraction with light density fraction (right graph)
PSCSPSCSPSCSPSCSPSCSPSCSPSPSPSPSPSPSPSCS0
10
20
30
40
50
60
Frac
tiona
tion-
light
(% o
f DM
to b
ulk)
Layer (-)
Upstream Downstream
0 10 20 30 40 50 60
0
5
10
15
Hy-
W (m
g/l)
Fractionation-light (% of DM to bulk)
Hyd
roph
ilic
frac
tion
(mg/
l)
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Prediction of organic matter degradability in river sediments (EGU2020-22064) J. Gebert1, F. Zander1
1Delft University of Technology, Dept. Geoscience and Engineering, Stevinweg 1, 2628 CN Delft, The Netherlands
Research questions:
• Can long-term degradation of sediment organic matter (SOM) be predicted from short-term degradation experiments?
• Is the relationship between short-term and long-term carbon mineralisation similar for different sites in Port of Hamburg and at any one site, for different layers?
Δ ?
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Relationship between short-term and long-term anaerobic C release by site, all layers included (SPM, FM, PS, CS)
• Upstream locations show higher anaerobic C mineralisation than downstream sites (compare Zander et al., 2020)
• Upstream locations show much higher correlation coefficients between short-term and long-term cumulative C-mineralisation
• At the most downstream point P9, which is also hydrodynamically most dynamic, inferring C mineralisation beyond 21 days from short-term measurements bears large uncertainty
• Slopes differ per site, higher slopes upstream, lower slopes downstream
x-axis: cumulative anaerobic C release after 10 days of incubation (G10), y-axis: cumulative C release after 21, 50, 100, 150 and 250 days
Zander, F., Heimovaara, T., Gebert, J. (2020): Spatial variability of organic matter degradability in tidal Elbe sediments. Journal of Soils and Sediments. DOI https://doi.org/10.1007/s11368-020-02569-4.
P1 RV
P2 RT
P8 KH
P9 SW
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00
2
4
6
8
10
12
14 G21 G50 G100 G150 G250
G21
, 50,
100
, 150
, 250
(mg
C/g
DW
)
G10 (mg C/g DW)
slope = 1.62, r = 0.99
slope = 2.43, r = 0.98
slope = 2.86, r = 0.97
slope = 3.13, r = 0.96
slope = 3.48, r = 0.93
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.60.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0 G21 G50 G100 G150 G250
G21
, 50,
100
, 150
, 250
(mg
C/g
DW
)
G10 (mg C/g DW)
slope = 1.44, r = 0.97
slope = 1.97, r = 0.92
slope = 2.32, r = 0.88
slope = 2.49, r = 0.80
slope = 2.78, r = 0.75
Up-stream
Down-stream
0.0 0.1 0.2 0.3 0.4 0.5 0.60.0
0.5
1.0
1.5
2.0
2.5
3.0 G21 G50 G100 G150 G250
G21
, 50,
100
, 150
, 250
(mg
C/g
DW
)
G10 (mg C/g DW)
slope = 1.42, r = 0.95
slope = 1.91, r = 0.85
slope = 2.08, r = 0.75
slope = 2.44, r = 0.76
slope = 2.99, r = 0.68
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.140.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0 G21 G50 G100 G150 G250
G21
, 50,
100
, 150
, 250
(mg
C/g
DW
)
G10 (mg C/g DW)
slope = 1.39, r = 0.96
slope = 1.90, r = 0.79
slope = 2.16, r = 0.61
slope = 2.27, r = 0.50
slope = 1.03, r = 0.09
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Relationship between short-term and long-term anaerobic C release by layer, all four sites included (P1, P2, P8, P9)
SPM FM
PS CS
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00
2
4
6
8
10
12
14 G21 G50 G100 G150 G250
G21
, 50,
100
, 150
, 250
(mg
C/g
DW
)
G10 (mg C/g DW)
slope = 1.62, r = 0.99
slope = 2.47, r = 0.98
slope = 2.94, r = 0.97
slope = 3.21, r = 0.96
slope = 3.51, r = 0.96
0.0 0.5 1.0 1.5 2.0 2.5 3.00
2
4
6
8
10
12 G21 G50 G100 G150 G250
G21
, 50,
100
, 150
, 250
(mg
C/g
DW
)
G10 (mg C/g DW)
slope = 1.56, r = 1.00
slope = 2.38, r = 0.99
slope = 3.08, r = 0.99
slope = 3.57, r = 0.99
slope = 4.11, r = 0.94
0.0 0.5 1.0 1.5 2.0 2.50
2
4
6
8
10
12 G21 G50 G100 G150 G250
G21
, 50,
100
, 150
, 250
(mg
C/g
DW
)
G10 (mg C/g DW)
slope = 1.58, r = 0.99
slope = 2.54, r = 0.99
slope = 3.41, r = 0.97
slope = 3.70, r = 0.97
slope = 4.56, r = 0.93
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.60
1
2
3
4
5
6
7
8 G21 G50 G100 G150 G250
G21
, 50,
100
, 150
, 250
(mg
C/g
DW
)
G10 (mg C/g DW)
slope = 1.57, r = 0.99
slope = 2.60, r = 0.97
slope = 3.59, r = 0.96
slope = 4.20, r = 0.94
slope = 4.82, r = 0.92
Top two
layers
Bottom two
layers
• Top layers show higher cumulative C mineralisation than deeper layers (compare Zander et al., 2020)
• High quality of correlation when sample pool is separated by layer rather than by site (previous slide)
• Larger variability in bottom layers PS and CS
x-axis: cumulative anaerobic C release after 10 days of incubation (G10), y-axis: cumulative C release after 21, 50, 100, 150 and 250 days
Zander, F., Heimovaara, T., Gebert, J. (2020): Spatial variability of organic matter degradability in tidal Elbe sediments. Journal of Soils and Sediments. DOI https://doi.org/10.1007/s11368-020-02569-4.
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Ratio of G250 to G10 along transect and by layer
• Factor between long-term and short-term C mineralisation is most uniform across all layers at upstream sites
• Higher variability of factor at downstream sites
• Difference between long-term and short-term anaerobic C mineralisation increases from upstream to downstream
RV PS RT PS KH PS SW PS0
10
20
30
40
Rat
io G
250/
G10
25%~75% 10%~90% Median Line Max 99% Mean 1% Min
RV FM RT FM KH FM SW FM0
10
20
30
40
50
60
Rat
io G
250/
G10
25%~75% 10%~90% Median Line Max 99% Mean 1% Min
RV SPM RT SPM KH SPM SW SPM0
5
10
15
20
25
30
35R
atio
G25
0/G
10 25%~75% 10%~90% Median Line Max 99% Mean 1%
RV CS RT CS KH CS SW CS0
5
10
15
20
25
Rat
io G
250/
G10
25%~75% 10%~90% Median Line Max 99% Mean 1% Min
SPM FM
PS CS
P1 P2 P8 P9 P1 P2 P8 P9
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Conclusions
• Organic matter with high degradability (e.g. algae) derived from upstream resulting in high
chlorophyll, silicic acid, biomass and EPS concentration as well as oxygen consumption.
• The hydrophilic DOC fraction (Hi) correlates well with fast organic matter degradation (e.g. light density fraction) and is therefore an indicator for high organic matter lability at upstream locations.
• Slowly degradable pool 3 material is found more often at downstream locations, easily accessible organic matter at upstream is degraded on its way downstream (age/source gradient).
• The pool determination is a suitable tool to separate between fast, intermediate and slow degradable organic matter.
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Conclusions
• Different sites along the transect P1 → P9 and the different layers are
characterised by different quality of SOM, reflected by different specific relationships between long-term and short-term C mineralisation
• Predictability of anaerobic C mineralisation increases when sediments are separated by layer rather than by site, indicating that specific SOM quality is associated with individual layers
• Higher uniformity of SOM mineralisation upstream may be due to single-source input (from upstream), whereas downstream locations receive OM from both upstream (river catchment) and downstream directions (North Sea) which is assumed to differ in composition/quality and degree of association with the mineral phase
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Thank you for your attention !
Contact: [email protected] and [email protected] www.tudelft.nl/mudnet