Controls of dissolved inorganic
and organic carbon discharge
from permafrost ecosystems
Prokushkin Anatoly S.
V.N. Sukachev Institute of Forest SB RAS, Krasnoyarsk
Siberian Federal University
[email protected]
ИЛ СО РАН: School of the young scientists on Biogeochemical
Matter Cycling In Permafrost Ecosystems
1
Presentation structure:
• Terms
• Processes
• Dissolved carbon in watersheds of
Siberian rivers : interactions of hydrology,
vegetation, permafrost, fires and C fluxes
2
• from Latin dissolvere :
dis- + solvere, to release
Physicochemical background:
Wikipedia: Dissolution is the process by which a solute
forms a solution in a solvent. The solute, in the case of
solids, has its crystalline structure disintegrated as separate
ions, atoms, and molecules form. For liquids and gases, the
molecules must be adaptable with those of the solvent for a
solution to form. The outcome of the process of dissolution
(the amount dissolved at equilibrium, i.e., the solubility) is
governed by the thermodynamic energies involved, such as
the heat of solution and entropy of solution, but the
dissolution itself (a kinetic process) is not. Overall the free
energy must be negative for net dissolution to occur. In turn,
those energies are controlled by the way in which different
chemical bond types interact with those in the solvent.
3
Dissolved carbon species:
• Dissolved inorganic carbon
[CO2*] + [HCO3−] + [CO32−]
• Dissolved organic carbon
Complex mixture of organic volecules
• Dissolved gases
CO2, CH4
Other portion of C in waters is called particulate C:
Particulate organic C
Particulate inorganic C
4
Dissolved carbon:
definitions and species
Initially in hydrochemistry dissolved matter is
operationally defined as
matter which is passed through 0.45 um pore-size filter
Wikipedia: …The "dissolved" fraction of organic carbon is
an operational classification. Many researchers use the
term "dissolved" for compounds below 0.45 micrometers,
but 0.22 micrometers is also common... A practical
definition of dissolved typically used in marine chemistry is
all substances that pass through a GF/F filter (0.7 um pore
size!).
So, to work with dissolved
carbon in a sample one need
first to filter sample!
5
Advantages and disadvantages of
filters:
• 0.22 micrometers: to get rid of microbes…
less loss during storage, but may contaminate
with C (nitrocellulose, acetate cellulose matrix)
• 0.7 um precombusted glass fiber filters
(GF/F): miserable or no contamination by OC,
but microbes…
6
How to measure?
• DOC (TOC = TC-IC, NPOC – nonpurgeable OC)
- The recommended measure technique is the
high temperature catalytic oxidation (IR
detection)
- Previous technique (still in use by Roshydromet)
Bichromate/permanganate oxidation
7
How to measure?
• DIC
- The recommended measure technique is
acidification with further IR detection
- Potentiometric titration with HCl for
alkalinity
H+ + HCO3- = H2CO3 = H2O + CO2
8
Why it is important?
• DOC loss from terrestrial ecosystems to fresh
waters constitutes 1-15% of NEP
• DIC and specifically dissolved CO2/CH4 fluxes
is not still well counted …
• C exported from terrestrial ecosystems to rivers
are rarely included in NEP estimates, causing its
underestimation
• DOM (DOC, DON, DOP etc…) is important
driver of foodwebs in both terrestrial and aquatic
systems
9
Dissolved organic C
• To be microbially mineralized to CO2/CH4
all organic matter must be dissolved
10
Dissolved inorganic C
Carbonate weathering…
H2CO3 + CaCO3 → Ca(HCO3)2
Silicate weathering…
2 KAlSi3O8 + 2 H2CO3 + 9 H2O ⇌ Al2Si2O5(OH)4 + 4 H4SiO4 +
2 K+ + 2 HCO3−
Temperature dependent process
high potential for sequestration of atmospheric CO2…
11
• Weathering of basalts of Central Siberian
Plateau may be important factor for atmospheric
CO2 sequestration
Illustration of the correlations between weathering fluxes and (A) thermal regimes and
(B) hydrological regimes for 22 representative silicate sites around the world (excerpt
from Beaulieu et al., 2010).
Our study shows clear increase of DIC annual yield from 1.04 gC m−2 yr−1 for
Tembenchi River (MAAT = −10.9 ◦C) to 2.77 gC m−2 yr−1 for Nizhnyaya Tunguska
River (MAAT = −7.5 ◦C).
The other basaltic boreal rivers such as Kamchatka River and its tributaries
(MAAT = −2.5 ◦C) exhibit significantly higher annual fluxes of DIC: 4.8 gC m−2 yr−1
12
Dissolved organic C:
dissolved or colloidal?
8000
7000
450
6000
[Na], ppb
400
350
[Fe], ppb
300
200
150
100
2000
1000
0
18.0
50
5 um
1.2 um
0.22 um
1 kDa
Pore diamter
300
250
10.0
600
8.0
500
6.0
400
0.22 um
1 kDa
0.22 um
1 kDa
300
200
0.0
December
100
March
April
May
June
July
September
100
Month
0
50
20 um
20 um
10 um
5 um
1.2 um
0.22 um
5 um
1.2 um
LMW
1 kDa
HMW
25
Pore diamter
10 um
Pore diamter
30
0
12000
20
0.02
0.015
0.01
10000
15
8000
[Ca], ppb
NPOC [mgC/L]
0.025
[Tb], ppb
1.2 um
700
12.0
2.0
150
5 um
14.0
4.0
200
10 um
Pore diamter
[K], ppb
10 um
NPOC [mgC/l]
20 um
20 um
LMW
HMW
16.0
0
[Al], ppb
4000
3000
LMW = 1 kDa
(Dialysis)
250
5000
10
5
6000
4000
0
2000
07.06.2013 07.06.2013 20.06.2013 20.06.2013 05.08.2013 05.08.2013
0.005
NT
KO
NT
KO
River/sampling date
0
20 um
10 um
5 um
1.2 um
Pore diamter
0.22 um
1 kDa
NT
KO
0
20 um
10 um
5 um
1.2 um
Pore diamter
0.22 um
13
1 kDa
What is DOC?
How to investigate the
composition?
• Complex mixture of organic molecules
• Fulvic acids (dissolved at pH 2)
• Hydrophobic acid (by XAD fractionation)
• Spectral characteristics (e.g. SUVA, spectral slope)
• Fluorescence (chromatophoric groups)
• Biomarkers (e.g. lignin, sugars etc.)
• Isotopic composition (i.e. 13C)
• Radiocarbon age (compound specific)
• Pyr-GC/MS-IRMS, 13C NMR CP MAS, electrospray ionization
Fourier transform ion cyclotron resonance mass spectrometry (ESIFT-ICR-MS)
14
• etc.
Dissolved organic carbon in
terrestrial systems
Rainfall
0.9-4.5 mgC/l
(< 0.5 gC/m2/a)
Throughfall/stemflow
0
6-70 mgC/l
(ca 1.0 gC/m2/a)
Soil Depth, cm
20
40
60
Jun
Jul
80
O
Ah
Aug
Sept
20-120 mgC/l
(2-18 gC/m2/a)
15-40 mgC/l
B
5-15 mgC/l
C
2-5 mgC/l
100
0
ALT
Time
Export to
stream
10
20
NPOC, mgC/l
30
5-31 mgC/l
2-10 gC/m2/a
40
15
moss
O layer
5 cm
20 cm
40 cm
35
30
Active layer
NPOC, mgC/l
5 cm
20 cm
25
20
15
10
5
0
1-Jun
40 cm
15-Jun 29-Jun
13-Jul
27-Jul 10-Aug 24-Aug 7-Sep 21-Sep
Sampling date
15
60 cm
10
5
Permafrost
0
5.8.09
May
September
Soil solution sampling and
temperature monitoring
19.9.09
3.11.09 18.12.09
1.2.10
18.3.10
2.5.10
16.6.10
31.7.10
-5
-10
Nfs 5 cm
Nfs 20 cm
Nfs 40 cm
16
-15
Terrestrial C links to aquatic
moss
O layer
0
10
Depth, cm
20
30
40
50
Sfs
Nfs
60
70
0
Active layer
20
40
60
80
DOC
Permafrost
17
Dissolved organic carbon in aquatic
systems
• Authochtonous
low C:N, high 15N, LMW, specific biomarkers
• Allochtonous (terrigenic)
High C:N, low 15N, low 13C, HMW, specific
biomarkers
18.0
LMW
HMW
16.0
NPOC [mgC/l]
14.0
12.0
10.0
8.0
6.0
4.0
2.0
18
0.0
December
March
April
May
Month
June
July
September
DOC production
• Biological
- Exudates
- Cell lysis
- Microbial breakdown of SOM
DOM
• Physical
Freeze-thaw cycles SOM
DOM
19
Terrestrial controls over C export:
soil C stocks and C:N ratio
Frey and Smith 2005, GRL
20
DOC “consumption”
• Microbial mineralization
DOC = CO2/CH4 + H2O
20
y = 0.6295x - 5.5604
DOC released or retained, mmol kg -1
10
• Sorption to mineral matrix
0
y = 0.6365x - 18.041
y = 0.6484x - 19.44
-10
y = 0.612x - 26.517
-20
y = 0.5812x - 32.144
-30
-40
Ah (05CP)
Ah (05BP)
B (05BP)
Bf (05BP)
B (05CP)
-50
0
• Precipitation
10
20
30
40
50
DOC added, mmol kg-1
0.80
0.80
0.60
0.50
0.40
0.30
0.20
0.10
50
y = 0.0138x + 0.3777
R2 = 0.9391
0.70
0.60
b, mmol DOC/kg
partition coefficient (m)
partition coefficient (m)
y = 0.0466x - 0.2044
R2 = 0.8213
0.70
0.50
0.40
0.30
0.20
0
5
10
Fe(d)
15
20
30
20
10
0.10
0.00
0.00
y = 5.8368x + 5.4781
R2 = 0.7657
40
0
0
10
20
SSA, m2/g
30
0.0
2.0
4.0
6.0
OC, mol C/kg soil
21
8.0
Permafrost and dissolved C:
A
Органический
слой
СТС
СТС
Periodic forest fires
?
мерзлота
мерзлота
Июнь
Июнь
Октябрь
Пожар
Октябрь
Послепожарная восстановительная сукцессия
B
Органический
слой
СТС
Permafrost degradation
мерзлота
СТС
мерзлота
Деградация мерзлоты
DOC
DIC
22
Arctic and subarctic ecosystems:
why dissolved carbon is important
• Largest amount of carbon (of which 1-2% is dissolved)
locked in soils and particularly conserved within the frozen
ground
(SOC = 1672 PgC, Tarnocai et al 2009)
• Dissolved carbon is most labile and indicative component of
soil C reservoir
• Highest rates of warming and permafrost degradation
• Highest sensitivity of ecosystem processes to ongoing
climate change
• Little is known about behavior of dissolved carbon in arctic
23
and subarctic watersheds
Global change: permafrost degradation
and an increase of active layer thickness
Monitoring sites
By 2091-2100, permafrost extent will be decreased 3075% and active layer thickness increased about 55-125
cm, compared to 1991-2010 (Park and Walsh 2013,
EGU General Assembly)
Implications for C export:
Higher retention times in soil (DOC negative)
Higher mineralization rates (DIC, pCO2 positive)
Higher weathering rates (DIC positive)
Positive trend in ALT depth
Negative trend in freezing depth
IPCC 2007,
24
from Frauenfeld et al 2004
Global change: hydrology
Eurasian river annual runoff to the Arctic Ocean tends
to increase for ca. 2.0 km3/year/year
(Peterson et al 2002, Science)
Implications for C export:
causes are debatable, but C export is
considered to be increased
(e.g. Gordeev and Kravchishina 2009)
25
Global change: vegetation
Figure from Dolman et al 2012, Biogeosciences
Changes and their effects on C export:
Net ecosystem productivity (likely +)
Northward shift of vegetation zones (likely +)
Desertification in Eastern and Central Siberia (-)
Shortened Fire Return Interval (-)
26
Studies of projected changes on
riverine C export
• Long-term monitoring data
• Space-for-time approach
Central Siberian Plateau:
RFBR-CRDF RUG1-2980-KR10 “Megaprojects”, RSF
Circum-polar studies:
Yenisey River basin:
Arctic-GRO (PARTNERS),
“Megaprojects”, RSF project project
Rosgydromet data
(Gordeev et al 1996)
2005 -…
2010-2012, 2013-2015…
27
Long-term monitoring: Rosgydromet
R-ArcticNet - A Database of Pan-Arctic River Discharge
http://www.r-arcticnet.sr.unh.edu/v4.0/main.html
28
General characteristics of Arctic rivers
11% of global freshwater input to the world ocean
>10% of global C export to the world ocean
Siberian sector:
Q, km3/a
DOC, Tg/a
DIC, Tg/a
Tg = 1012 g
Ob’
Yenisey
Lena
Kolyma
sum
427
4.12
6.15
636
4.65
6.66
581
5.68
5.43
111
0.82
0.70
1755
15.3
18.9
% of 6 major % of total
Arctic rivers to the AO
77.6
84.3
67.0
35.1
44.8
Source: Gordeev et al 1996, 2009, Raymond et al 2007,
Striegl et al 2007, Cai et al 2008, Cooper et al 2008,
McGuire et al 2009, Holmes et al 2011, Prokushkin 29
et al
2011, Amon et al 2011
Recent estimates of carbon in rivers…
Dolman et al. 2013 Biogeosciences (based on Meybeck et al., 2006)
East Kara sea (Yenisey)
West Kara sea (Ob)
13%
19%
East Laptev sea (Kolyma)
West Laptev sea (lena)
!
17%
28%
35%
39%
DIC flux
DIC flux
DIC flux
DOC flux
DOC flux
DOC flux
DOC flux
POC flux
POC flux
POC flux
POC flux
DIC flux
31%
56%
22%
61%
42%
37%
7.7 TgC/a
11.1 TgC/a
9.6 TgC/a
2.4 TgC/a
McGuire et al. 2009, Ecol Monogr (based on numerous sources)
Yenisey
1%
Ob
4%
Kolyma
Lena
6%
!
16%
33%
29%
41%
35%
59%
58%
67%
51%
9.9 TgC/a
12.8 TgC/a
9.9 TgC/a
2.3 TgC/a
30
Basin characteristics
Amon et al 2011, GCA
31
Seasonality of Hydrology and C
fluxes in major Siberian Rivers
60
freshet
summer-fall
winter
90000
60000
3
Discharge, km /month
70000
R-ArcticNet
50000
40000
30000
50
% of annual runoff
80000
Ob'
Yenisey
Lena
Kolyma
40
30
20
20000
10
10000
0
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
0
Dec
Ob'
Yenisey
Lena
70
Kolyma
spring
summer-fall
winter
60
% of annual DOC flux
Jan
50
40
30
20
10
0
Ob’
Welp et al 2005, GRL
Yenisey
Lena
Kolyma
Freshet (May-June)
water flux: 30-50%
C flux: 30-60%
Holmes et al 2011 Estuaries and Coasts
32
Major Arctic Rivers Dissolved C:
annual values
8
30
а)
25
DIC
b)
DOC
15
10
(gC m-2 a-1)
Annual C export
6
20
4
2
Yukon
Mackenzie
Аmguema
Kolyma
Yana
Indigirka
Lena
Khatanga
Ob
Yenisey
Tembenchi
Nidym
Kochechum
P.Tunguska*
N. Tunguska**
Yukon
Mackenzie
Аmguema
Kolyma
Yana
Indigirka
Lena
Olenek
Anabar
Yenisey
Khatanga
Ob
Tembenchi
Nidym
Kochechum
P.Tunguska*
0
Olenek
0
Anabar
5
N. Tunguska**
(mgС l-1)
Mean annual C concentrations
Gordeev et al 1996, 2009, Raymond et al 2007, Striegl et al 2007, Cai et al 2008, Cooper et al
2008, McGuire et al 2009, Holmes et al 2011, Prokushkin et al 2011, Amon et al 2011
Rivers of Arctic Ocean basin
Rivers of Arctic Ocean basin
Decreasing trend of concentrations
and annual fluxes from West to East,
specifically for DIC
Limitation for response prediction:
-Data quality
-Different parent materials
-Disturbances
33
Case study in Western Siberia:
Ob’ basin (Frey and Smith 2005, GRL)
Projected “2.7–4.4 Tg yr-1 increase in terrestrial DOC flux (from 9.2 Tg yr-1 to
11.9–13.5 Tg yr-1) from West Siberia to the Arctic Ocean by 2100.
These estimates are in fact conservative if DOC concentrations peak during spring
flood. Furthermore, if the recently observed increases in Siberian precipitation
[Serreze et al., 2000; Frey and Smith, 2003] and river discharge [Peterson et al.,
2002; Wu et al., 2005] continue, even larger increases are likely.”
34
Central Siberian River basins and
study goals
Yenisey River basin
Central Siberian Plateau
river basins
Gradients:
Climate, permafrost,
vegetation, parent rocks
Gradients:
Climate, permafrost,
vegetation,
SIMILAR parent rocks
(Siberian basalts)
Stream basins within
Nizhnyaya Tunguska
river watershed
Gradients:
Fire history (burned 0, 4, 20,
50 and >100 years),
permafrost, vegetation, size,
SIMILAR: climate, parent
rocks (Siberian basalts)
35
Yenisey River basin characteristics
36
100
5
permafrost
Total C flux
80
4
60
3
40
2
20
1
0
TC flux g/m2/June
Continuous permafrost, %
Yenisey basin: DOC and DIC
0
-12
-10
-8
-6
-4
-2
0
MAAT, oC
Cryohydromorphic landscapes of 61-65oN latitude zone
produce elevated C fluxes
40
Dissolved carbon [mgC/l]
35
30
25
DIC
20
15
10
DOC
69о45'30.6''
Енисей
66о25'7.41''
58о01'01.3''
Енисей
65о36'04.6''
51o42'
Енисей
63о15'09.7''
51o26'
0
60о54'18.1''
5
Енисей
Енисей
Енисей
Енисей
Енисей
sampling stations
37
Total C flux in Yenisey River from South to North shows substitution of IC to OC
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pCO2 [ppm]
Yenisey basin: dissolved gases
4000
3500
3000
2500
2000
1500
1000
500
0
100
10
1
0.1
River flows showed supersaturation by GHG (relative to
atmospheric levels), reflecting large flux of C to the Arctic
Ocean in gaseous form
38
River basins of
Central Siberian
Plateau
39
Prokushkin et al 2011, ERL
Hydrology of rivers of Central
Siberian Plateau
25000
Freshet (May-June) water flux: >60%
Daily discharge, m3/s
20000
15000
10000
5000
01.10.12
01.07.12
01.04.12
01.01.12
01.10.11
01.07.11
01.04.11
01.01.11
01.10.10
01.07.10
01.04.10
01.01.10
01.10.09
01.07.09
01.04.09
01.01.09
01.10.08
01.07.08
01.04.08
01.01.08
01.10.07
01.07.07
01.04.07
01.01.07
01.10.06
01.07.06
01.04.06
01.01.06
0
-12,0
NT
-14,0
KO
d18O
-16,0
-18,0
1% a year
-20,0
-22,0
-24,0
-26,0
1.10.05
29.5.06
24.1.07
21.9.07
18.5.08
13.1.09
10.9.09
8.5.10
3.1.11
31.8.11
Date
Prokushkin et al 2011, ERL
40
Dissolved carbon in Central Siberia
50
Discharge
Discharge [m3/s]
20000
DOC
45
DIC
40
35
15000
30
25
10000
20
15
5000
Concentrations [mgC/l]
25000
10
5
0
28.05.2005
10.10.2006
22.02.2008
06.07.2009
18.11.2010
01.04.2012
0
14.08.2013
Freshet (May-June)
55–71% for water runoff
64–82% for DOC
37–41% for DIC
Temporal and Spatial variation of DOC, DIC:
Dominance of snowmelt season and increased flux in
wet years
Large differences in amounts of DIC and DOC among
rivers (for DIC causes are still questionable)
41
8
30
а)
25
DIC
b)
DOC
15
10
(gC m-2 a-1)
Annual C export
6
20
4
2
Yukon
Mackenzie
Аmguema
Kolyma
Yana
Indigirka
Lena
Khatanga
Ob
Yenisey
Tembenchi
Nidym
Kochechum
P.Tunguska*
N. Tunguska**
Yukon
Mackenzie
Аmguema
Kolyma
Yana
Indigirka
Lena
Olenek
Anabar
Yenisey
Ob
Tembenchi
Nidym
Kochechum
P.Tunguska*
N. Tunguska**
0
Olenek
0
Anabar
5
Khatanga
(mgС l-1)
Mean annual C concentrations
Dissolved carbon in rivers of
Central Siberian Plateau
Rivers of Arctic Ocean basin
Rivers of Arctic Ocean basin
25
20
y = 4.2629e 0.0132x
R2 = 0.7721
DOC
DOC concentrtions, mgC/l
Positive correlation with MAAT, forested
areas (Prokushkin et al 2011, ERL)
DOC/DIC concentrations, mgC/l
Decreasing trend of concentrations and
annual fluxes from South to North
25
A
y = 1.8607x + 29.371
2
R = 0.6577
15
y = 1.5256x + 20.032
R2 = 0.89
10
DIC
5
B
20
15
10
5
0
0
-12
-10
-8
-6
MAAT, oC
-4
-2
0
0
20
40
60
80
Conifer forest coverage, %
100
42
120
Coniferous forests are the major source of DOC!
1000
Lignin S8 [ug/L]
100
NT
10
KO
Ob'
Yenisey
Lena
Kolyma
120000
1
300
0
4.0
80000
200
60000
150
40000
100
20000
50
2.0
0
0
28.6.03
14.1.04
1.8.04
17.2.05
Date
5.9.05
24.3.06
10.10.06
28.4.07
10
15
NPOC [mgC/L]
20
25
NT
1.0
10.12.02
5
Data:
ArcticGRO, PARTNERS
(http://www.arcticgreatrivers.org/data.html)
Prokushkin et al unpublished
3.0
SUVA (m/l/mgC)
250
Sig8. ng/l
Discharge, m3/s
Q
lignin
100000
KO
0.0
0.01
0.1
1
Discharge (m3/s)
10
100
43
DOC composition (unexplained patterns):
Pyr-GC/MS-IRMS, 13C NMR CP MAS data
60
Anaheim lake
(USA)
Phenolics
Proteinaceous
40
Alkylaromatics
NT 03.08.2008
30
NT 28.08.2009
20
NT 03.06.2010
10
NT 19.07.2010
0
21-May
11-Jun
2-Jul
23-Jul
13-Aug
3-Sep
NT 16.08.2010
Date
NT 15.09.2010
350 300 250 200 150 100 50
0
-50 -100-150
chemical shift (ppm)
-25
-26
-27
 13 C [‰]
Relative amount [%]
Carbohydrates
50
KO 01.06.2008
African
swamp
-28
KO 28.08.2009
-29
-30
-31
KO 09.06.2010
-32
2-Methoxy-phenol
Ethybenzen
2,4-Pentadienal
-33
-34
20-May
17-Jun
15-Jul
12-Aug
KO 19.07.2010
KO 16.08.2010
9-Sep
Date
KO 15.09.2010
300 250 200 150 100 50
0
-50 -100-150
chemical shift (ppm)
• Surprisingly little seasonal and geographic variation in riverine DOM composition
• Large temporal changes in 13C signature of individual compounds
44
Dissolved GHG
3500
[CO2] ugC/l
3000
2500
2000
1500
1000
500
0
5
31.05.12
20.06.12
10.07.12
30.07.12
19.08.12
08.09.12
28.09.12
[CH4] ugC/l
4
3
2
1
0
31.05.12
Kochechum
N Tunguska
20.06.12
10.07.12
30.07.12
19.08.12
08.09.12
28.09.12
River waters are supersaturated with GHG
Dissolved GHG is important portion in total C flux
(10% of total DC)
45
Future of C export from
Central Siberian Plateau
N Tunguska River: the Southern
part of Central Siberian Plateau
Kochechum River: the Northern
part of Central Siberian Plateau
Only projected increase in water flux to 2100 (e.g. 0.33 km3/year/year
for N Tunguska River) may almost double terrestrial C export to rivers
Together with an increase in NEP/terrestrial C accumulation of
Northern territories it may increase total C flux up to 700% of current
values (e.g. Gordeev and Kravchishina, 2009, Frey and Smith, 2005)
Prokushkin et al 2011, Doklady Earth Sciences
46
DOC behavior concept: latitude
DOC concentration [mgC/l]
Boreal deciduous
conifer forests
Evergreen taiga and
mixed boreal forests
Forest-tundra, tundra
High labile C
Hydromorhism
Permafrost
Climate change
Low productivity
Low labile C
Mineralization
Retention in soil
Mineralization
50
55
60
65
Latitude [oN]
70
75
Gymnosperm vegetation (the middle of boreal belt) is the primary source of
DOC in Arctic rivers (A. Myers-Pigg et al submitted).
47
DOC/DIC/pCO2 behavior
100%
90%
DIC
70%
60%
DIC/p CO2 [mgC/l]
DIC/DOC proportion
80%
Climate change
50%
40%
30%
DOC
20%
10%
0%
Freshet
Seasonal changes:
Summer-fall
Winter
50
55
60
65
70
75
Latitude [oN]
Retention in soil, DOC mineralization and rock weathering rates tend to increase
Result: substitution of DOC for DIC in total carbon flux
(TC changes might be negligible (Striegl et al., 2005, 2007))
48
Wildfire effects
ca. 1% of territory burned annually
MODIS (modeled GPP)
Major Siberian Rivers:
Central Siberian streams
Fire year of 2003
burned 4, 20, 65 and >100
years ago
Central Siberian Rivers
Fire scars demonstrate low NPP:
territories have potentially higher DOC production at no fire scenario
49
2013…
July 20,
2013
August 6, 2013
35
30
NPOC
SO4
30
25
25
15
15
SO4, mg/l
NPOC, mgC/l
20
20
10
10
5
5
0
6.5.13
0
26.5.13
15.6.13
5.7.13
25.7.13
14.8.13
3.9.13
23.9.13
13.10.13
Date
50
Stream C fluxes in post fire
chronosequence
Changes in DOC, SUVA, DIC and specific conductivity (SC) of streams draining watersheds of different fire history.
Note log scale for SC. Parham et al, 2013, submitted to Biogeochemistry
Fires combusting OM and deepening the ALT
- decrease DOC release from basins,
- increase the release of DIC and other inorganic solutes
- change in DOM composition (e.g. lower aromaticity of released DOC)
Recovery of ecosystem structure in ca. 50 years after a fire coincides with the
recovery of stream C fluxes
51
Pyrogenic carbon (dissolved black carbon, DBC)
is intrinsic component of Siberian riverine DOC
Nizhnyaya Tunguska River
25
1000
800
15
600
10
400
5
200
0
0
J
F
J
J
2006
A
S
O
N
D
Q
1000
BC
800
12
10
600
8
400
6
4
200
y = 0.0229x - 0.1757
R2 = 0.8601
0
0
J
F
M
A
M
J
J
A
S
O
N
D
2006
0.3
DBC concentrations in rivers of Central Siberian
Plateau.
Prokushkin et al, unpublished
0.2
0.1
0.0
0
5
10
15
NPOC [mgC/l]
20
25
30
DBC versus DOC concentrations of Siberian rivers.
Myers-Pigg et al 2013, ASLO meeting
52
BC-BPCA (mgC/l)
3
Discharge (1000 m /s)
M
2
0.4
BC-BPCA [mgC/l]
A
b
14
0.5
M
Kochechum River
16
DBC versus DOC concentrations of global rivers.
Jaffé et al 2013, Science
BC-BPCA (mgC/l)
20
3
Discharge (1000 m /s)
a
Indicators of permafrost
degradation
1000
N10
Cl- (mg/l)
100
10
N2
N15
1
N13 N9 N14
0.1
0.01
1
10
100
1000
10000
Basin area (km2)
100000 1000000
Evaporite signal as NaCl/CaCl2 appeared in
river/stream waters through “through taliks” and
wildfires may accelerate this process
Parham et al, 2013, Biogeochemistry
53
Wildfire effect
Implication for C export:
• Combustion products of terrestrial OM constitutes up 8%
of DOC in Siberian rivers
• Combustion of C source leads to decreased DOC
production in terrestrial ecosystems and lower release to
rivers
• Deepen active layer leads to higher retention of DOC in
soils and lower DOC release, but higher mineralization
and weathering rates cause elevated DIC flux
• DOC flux from large Siberian rivers can be potentially
larger with no fire scenario
54
Conclusions
• Rivers draining Siberia demonstrate significant potential to increase the
release of terrestrial carbon to the Arctic Ocean. Increased hydrological
C losses are projected through:
(i) enhancement of temperature-controlled DOC, DIC, POC and CO2
production processes within watersheds;
(ii) raised precipitation, thereby increasing C mobilization from organic-rich
layers;
(iii) introduction of a new source of C as NEP increases/vegetation shifts
northward and
(iv) release of old C from degrading permafrost
Increased DOM (C,N and P) input may significantly change
NPP in river, estuarine and ocean ecosystems
Dry scenario of warming in high latitudes undoubtedly leads to decreased terrestrial C export
due to:
• inhibition of DOC production in terrestrial ecosystems and less DIC and pCO2/pCH4 transport
• shorten fire return interval, removing the source of OC in terrestrial ecosystems
55
Thank you for
attention!
Acknowledgements
Thanks all colleagues from IF SB RAS, GET-CNRS, MPI-BGC, TAMUG, Uni
Hannover, FFPRI and others for joint field and laboratory works and constructive
discussions.
56
Themes for working groups
• 1. Compare C concentrations and fluxes
by major Siberian rivers: spatial patterns
and different estimates...
• 2. Calculate flow-weighted mean annual C
concentrations for Siberian rivers.
• 3. Analyze elements bound to DOC
• 4. Calculate seasonal C fluxes
57