1

Old carbon in the modern marine environment

Possible origin(s) of non-zero 14C ages for OC carbon in marine surface sediments:

• 1. Delivery of “pre-aged” terrestrial OC of vascular plant origin

• 2. Relict OC (“kerogen”) inputs from erosion of sedimentary rocks

• 3. Sediment redistribution processes- Bioturbation- Lateral advection

• 4. Black Carbon

The Global Organic Carbon Cycle (ca. 1950)

ATMOSPHERIC CO2(750)

SEDIMENTARY ROCKS

(KEROGEN) (15,000,000)

-20 to -35‰t = infinite

LAND PLANTS (570)

-25 to -30‰ (C3) -14 to -20‰ (C4)

t = 0 yr

SOIL HUMUS (1,600)

-25 to -30‰ (C3) -14 to -20‰ (C4) t =10-10,000 yr

OCEAN (BIOTA) (3)

-20 to -30‰ (C3) t = 400 yr

RECENT SEDIMENTS (100)

-20 to -25‰t = ?? yr

uplift

burial

physical weathering

(0.2)

net terrestrial primary production

(50)

humification(50)

river or eoliantransport

(POC=0.15)

fossil fuel utilization

OC preservation (0.15)

(units=1015gC)

Modified after Hedges (1992)

net marine primary

production (50)

sediment redistribution

2

0

1

2

3

4

5

6

-250 -150 -50 50 150 250

∆14C

z (c

m)

1899

1913

1937

1961

1985

1996

Benthic forams

TOC

Planktonic forams

DIC

TOC and foraminiferal ∆14C in Santa Monica Basin sediments

-200

-150

-100

-50

0

50

100

150

-35 -30 -25 -20 -15δ13C

∆14

C

SMB 0-1SBB 0-1SMB 5-6-86 ± 19 ‰

+59 ± 26 ‰

SMB, TOC

SMB, TOC

14C contents of algal sterols in CBB sediments

Post-bomb DIC

Pre-bomb DIC

Data from Pearson et al. (2000)

3

Ross Sea, Antarctica

2760-24.041.05827Chinstrap

6500-26.350.49670Emperor

4070-27.420.34623Gentoo

9990-25.650.24671Fairy

14C age

δ13CTOC (%)

Water Depth

(m)

SiteSurface Sedimentary OC composition

Data source:Ohkouchi et al. (2003)

Ross Sea

Antarctica

C14 fatty acidC16 fatty acidC18 fatty acidTOC

0

5

10

15

Dep

th in

cor

e (c

m)

Calendar year (yr BP)

Post

-bom

b D

IC

Pre-

bom

b D

IC

0 1000 2000 3000 4000

Fatty acid and TOC 14C chronologies for Ross Sea sediments

(OxCal3 calibration)

Data source:Ohkouchi et al. (2003)

Chinstrap Site

15 cm/kyr

7.5 cm/kyr

4

Coupled molecular and microfossil 14C measurementsPremise:

• Marine algal biomarker compounds (e.g., alkenones) and planktonic forams both encode surface ocean-derived signatures (incl. 14C content of DIC).

• Age discrepancies must therefore indicate different subsequent fates.

• Marine organic matter is predominantly associated with the fine fraction of sediments – prone to resuspension and redistribution.

• Foraminiferal tests are coarse, sand-sized particles – less susceptible to redistribution by bottom currents.

Approach:

• Use 14C relationships between planktonic foraminifera, algal biomarkers (e.g., alkenones), and bulk OC isolated from the same sediment intervals as a tool to examine sedimentological processes (lateral transport, bioturbation).

C37 “alkenone” E. Huxleyi

0

500

1000

1500

2000

10 20 30

%CaCO3

Age

(Cal

enda

r yea

rs)

0.6 0.8

UK37'

0 5000

alkenones0 5000

TOC0 5000

FFIC

Age difference (vs planktonic forams)

Ohkouchi et al. 2002

Sedimentological Controls on Geochemical Records from the Bermuda Rise

5

Cape Cod

Nova Scotia

Bermuda

SeaWiFS satellite image of E. huxleyibloom off Newfoundland in the western Atlantic on 21st July, 1999.

6

?

Long-range transport of organic matter (and alkenones) from the ScotianMargin to the Bermuda Rise?

?

Lateral transport of organic matter to the Bermuda Rise

7

?

Lateral transport of organic matter to the Bermuda Rise

Sources and Transport of Alkenones and Forams to the Bermuda Rise

SCOTIAN MARGIN

TERRIGENOUS SEDIMENT

PARTICLE RESUSPENSION

PLANKTONIC FORAMS

CaCO3

WARM ALKENONES

COLD ALKENONES

BERMUDA RISE

SCOTIAN MARGIN

TERRIGENOUS SEDIMENT

PLANKTONIC FORAMS

CaCO3

WARM ALKENONES

COLD ALKENONES

BERMUDA RISE

N

N

ADVECTION OF OLD, COLD ALKENONES ON

CLAYS/SILTS

PRESENT DAY

LITTLE ICE AGE

FOCUSSING

FOCUSSING

SARGASSO SEA

SARGASSO SEA

ADVECTION OF OLD, COLD ALKENONES ON

CLAYS/SILTSLAURENTIANFAN

LAURENTIANFAN

PARTICLE RESUSPENSION

COLD SST

COLD SST

WARM SST

WARM SST

8

Science goes in circles!

HEBBLEStudy area

Namibian margin (Benguela Upwelling region)

Namibia

-5500

-4500

-3500

-2500

-1500

-500

0

1000

Elevation

(m)

0-2 cmalkenones and bulk OC

modern age

2-12 cm (pre-bomb)alkenones: 1180 yrs

~ Reservoir age

0-1 cmalkenones 2500 yrbulk OC 2270 yrforaminifera 25 yr

Data from Mollenhauer et al., 2003

9

14C ages of Namibian margin sedimentary components (core 226660-5)

160

140

120

100

80

60

40

20

0

0 5000 10000 15000

Total organiccarbon

Alkenones

14C age (yr)

Dep

th (c

m)

Plantonic forams( G. bulloides)

Alkenones

Total organiccarbon

0 1000 2000 3000 4000 5000

14C age difference vs forams (yr)

Mollenhauer et al., 2003

Accumulation maximum (depocenter) on upper continental slope

20 m

Distance [km] 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190

Wat

er D

epth

[m]

(Vp=

1500

m/s

)

1000

1600

1400

1200

SNa)

b)

erosion?increased

accumulation

Seismic data processing: André Janke

TOC

(%)

012345678910

8 9 10 11 12 13 14 15 16 17

-30

-29

-28

-27

-26

-25

-24

-23

-22

-21

-20

-19

Walvis Bay

Lüderitz

Sites of increasedaccumulation in protectedlocations (depocenters):Implication of currentcontrolled sedimentation

Mollenhauer et al., 2002

10

Southern Chile

0

2000

4000

6000

8000

Con

vent

iona

l 14C

age

(yr B

P) GeoB3313-1

Chile

0 200 400 600 800Core depth (cm)

-10000

10002000300040005000

∆14

C a

ge (y

r)

bulk OC

planktic foraminifera

alkenones

alkenones - forams

bulk OC - forams

Chile

Mollenhauer et al. In press.

-1000

0

1000

2000

3000

4000

5000

6000

7000

8000

Age

diffe

renc

e (14

C y

ears

)

Sample

Bermuda Rise Namibian Slope Chilean Margin NW African Slope Santa Barbara Basin Namibian Shelf Scotian Shelf (Emerald Basin) New England Shelf (Mud Patch) Gulf of Mexico Oman Margin Indian Ocean

Closed symbols = Alkenone-foram age discrepancyOpen symbols = TOC-foram age discrepancy

14C age discrepancies between organic matter and calcareous microfossils

Eglinton et al. unpublished

11

-10

0

10

20

30

40

50

60

Adve

cted

alk

enon

e co

ntrib

utio

n (%

) Bermuda Rise Benguela Scotian Margin New England margin Gulf of Mexico Arabian Sea Santa Barbara Basin Indian Ocean NE Pacific Ocean ( (Stn M))

Estimates of advective alkenone contributions

Assumptions:∆14C of indigenous alkenones = ∆14C of forams∆14C of advected alkenones = -1000 permil (infinite 14C age)

Eglinton et al. unpublished

-600 -500 -400 -300 -200 -100 0 100

-600

-500

-400

-300

-200

-100

0

100

∆14

C a

lken

ones

(per

mil)

∆14C bulk OC (permil)

Core tops only (0-5 cm)

Eglinton et al, unpublished

Comparison of alkenone and TOC 14C agesin surficial (< 3 cm) marine sediments

12

Additional evidence for advective OC supplyto the sea floor

(i) Increased material fluxes in deep, relative to shallow, sediment traps deployed near continental slopes (Honjo et al., 1982; Biscaye et al., 1988; Thomsen & van Weering, 1998).

(ii) High suspended particle concentrations near the seafloor (bottom nepheloid layer; McCave, 1983; Gardner & Sullivan, 1981) or associated with the detachment of intermediate nepheloid layers from the upper slope (INLs; Biscaye et al., 1988; Pickart, 2000).

(iii) Carbon and oxygen imbalances in the deep ocean (Jahnke et al., 1996).

(iv) Old 14C ages of OC on suspended particles in slope waters (Bauer et al., 2001).

(v) 14C age of particles on slope waters intercepted by sediment traps (Anderson et al., 1994; Hwang et al., 2004).

(vi) The isotopic and molecular composition of deep sea sediments (Freudenthal et al.,2001; Benthien & Müller, 2000).

Advection of POC in the Panama Basin

Druffel et al., 1998

13

Benthien & Muller, 2000

Lateral transport of alkenones to the Argentine Basin

Vertical Transport of Organic Matter to the Sea Floor

14

Lateral Transport of Organic Matter to the Sea Floor

-1000

-800

-600

-400

-200

0

G. r

uber G. i

nfla

ta

TOC

(0-1

cm)

TOC

(1-2

cm)

Alke

none

s (0

-1cm

)Al

keno

nes

(1-2

cm)

C16

fatty

aci

dC

18 fa

tty a

cid

C24

fatty

aci

dC

26 fa

tty a

cid

C28

fatty

aci

d

C21

+C23

+C25

alk

anes

C22

+C24

+C26

alk

anes

C27

alk

ane

C29

+C31

alk

anes

C28

+C30

+C32

alk

anes

UC

M

∆14

C (p

erm

il)

planktonic forams total organic carbon alkenones fatty acids hydrocarbons

14C age variability in Bermuda Rise surface (0-3 cm) sediment

0

1000

2000

3000

4000

5000

10000

15000

2000030000

14C age (yr B

P)

15

Calculation of % terrestrial, marine and fossil OC

∆14CTOC = fmarine * ∆marine + fterrestrial * ∆terrestrial + ffossil * ∆fossil

δ13CTOC = fmarine * δmarine + fterrestrial * δterrestrial + ffossil * δfossil

fmarine + fterrestrial + ffossil = 1

Variable Measurement/assumption:∆14CTOC measure directly (AMS)δ13CTOC measure directly (irMS)∆14Cmarine measure phytoplankton sterol (PCGC/AMS)∆14Cterrestrial measure lignin phenol/plant wax (PCGC/AMS)∆14Cfossil stipulate as –1000 ‰δ13Cmarine measure phytoplankton sterol (irm-GC-MS)

- assume offset between biomarker and bulk OCδ13Cterrestrial measure lignin phenol/plant wax (irm-GC-MS)

- assume offset between biomarker and bulk OCδ13Cfossil assume value based on regional stratigraphy

- (or measure biomarker selected based on ∆14C)

Dual isotopic mass balance approach:

Arab

ian

Sea

Beng

uela

Upw

ellin

Sant

a M

onic

a Ba

sin

Blac

k Se

a U

nit I

Blac

k Se

a U

nit I

I

Berm

uda

Ris

e

Was

hing

ton

Mar

gin

St2

Was

hing

ton

Mar

gin

St1

Gul

f Of M

exic

o

Beau

fort

Sea

Ros

s Se

a (C

hins

tra

Ros

s Se

a (G

ento

o)

Ros

s Se

a (E

mpe

ror)

Ros

s Se

a (F

airy

)

Arabian Sea

Benguela Upwelling

Santa Monica Basin

Black Sea Unit I

Black Sea Unit II

Bermuda Rise

Washington Margin St2

Washington Margin St1

Gulf Of Mexico

Beaufort Sea

Ross Sea (Chinstrap)

Ross Sea (Gentoo)

Ross Sea (Emperor)

Ross Sea (Fairy)

0

10

20

30

40

50

60

70

80

90

100-712

-25.65-555

-26.35-395

-27.42-300

-24.04-600

-22.68-251-20.7

∆14C TOCδ13C TOC

-109-21.7

-160-23.0

-108-24.2

-876-28.26

-136-25.24

-468-25.36

-570-21.7

-194-25.29

%

marine vascular plant relict

Dual Isotope Mass Balance

16

Black Carbon (BC)

Suggested Reading:

• Gustafsson O. and Gschwend P.M. (1998) The flux of black carbon to surface sediments on the New England continental shelf. Geochim. Cosmochim. Acta 18, 805-829.

• Masiello C.A. and Druffel E.R.M. (1998) Black Carbon in Deep-Sea Sediments. Science 280, 1911-1913.

• Schmidt M.W.I. and Noack a.g. (2000) Black carbon in soils and sediments: Analysis, distribution, implications and current challenges. GBC 14, 777-793.

• Masiello C.A. (2004) New directions in black carbon organic geochemistry. Mar. Chem. 92, 201-213.

17

Org. Matter + O2 CO2 + H2O

(NB. For PAH, also read BC!)

18

Black Carbon (BC)

Some Notes:• Estimates of modern BC production• Biomass burning: 50-260 Tg C/year• Fossil fuel combustion: 12-24 Tg C/year• Atmospheric lifetime of BC aerosols: 40 hours to 1 month• Mass of organic carbon stored globally in ocean sediments: 160 Tg/year • BC estimated to make up ca. 6% of sedimentary OC globally.• Locally (on margins) BC may comprise up to 50% of TOC.

Tons emitted Tons emitted

50000

20000

10000

5000

1000

5000

1000

500

100

10

Biomass BurningFossil Fuel Combustion

Scatter Absorb

Contributions of Black Carbonto Greenhouse Warming

BCOther particulateaerosols

Cooke & Wilson (1996)

Kirkevag et al. (1999)

19

Public Health

Increased respiratory problemsassociated with elevated particulatematter concentrations

Black Carbon – A moving Target!(The Combustion Continuum)

Schmidt et al. (1999)

20

What is Black Carbon?

How can we analyze BC?

21

BC isolation/measurement methods

3 main types of method:• optical• chemical oxidation• thermal oxidation

NB: In almost all cases, BC is operationally defined.– Leads to very different estimates of quantity and flux of BC.

Carbon isotopic characterization of BC based

on thermal oxidation(“Gustafsson”) method

Modified by Reddy

22

Glacial

Interglacial

Verardo & Ruddiman (1996)200

180

160

140

120

100

80

60

40

20

00.0 0.2 0.4 0.6 0.8 1.0 1.2

Charcoal (%)

Age

(ka)

Middelburg et al. (1999)

Supply of BC to marine sediments

Proportions of BC in marine sediments

23

14C age of Black Carbon in marine sediments

Masiello and Druffel 1998, Science

Non-BC BCNB. BC isolated by chemical wet oxidation method

BC in Santa Clara River suspended sediments

Masiello and Druffel, 2001, GBC

24

BC in Santa Monica Basin sediments

Masiello and Druffel 2003 GRL

Proportions of BC in marine sediments

Middleburg et al 1999

25

Graphitic Black Carbon (GBC) in(pre-anthropogenic) Washington Margin sediments

Dickens et al. 2004, Nature

Guo et al. 2004, GBC

26

649 ± 143-80.8-27.912 µgPlant wax alcohols

2070 ± 35-231.7-15.130.24 %Black Carbon

1260 ± 40-149.6-18.931.02 %Total Organic Carbon

14C age(yr BP)

∆14C(‰)

δ13C(‰)

Concn. (gdw basis)Fractions

Eglinton et al., G3, 2002

Carbon isotopic composition of dustfall sample off NW Africa

Molecular Proxies for BC

27

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

1880

1900

1920

1940

1960

1980

0.000 0.002 0.004 0.006 0.008

Year

of D

epos

ition

Organic Carbon (g OC / g sed)

Soot Carbon (g SC / g sed)0 4 8 12 16

1880

1900

1920

1940

1960

1980

PAH concentration (ug/g)

Gustafsson et al. (1997)

Historical records of combustion inputs to the environment

Pre-1880’s: Wood Combustion

1900-1950: Heavy industrializationUtilization of Coal

1970-2000: Catalytic convertersPhase-out of Pb gasoline

1950-1970: Change from coal to oilPeak of Pb gasoline use

28

Pettaquamscutt River Basin

1900 1925 1950 1975 2000

40

30

20

10

0

Year of Deposition

210Pb Model

1965 ± 1

40

30

20

10

0

0.0 0.2 0.4 0.6 0.8

1952 ± 1

1987 ± 1

137Cs (dpm.g-1)

Dep

th (c

m)

1800

1820

1840

1860

1880

1900

1920

1940

1960

1980

20000 100 200 300 400 500

Flux (ng cm-2 yr-1)

Year

of D

epos

ition

19301945

19601974

Sum of 15 parentPAH (excluding perylene)

1890

Down-core variations in PAH fluxes

29

Petrogenicsource ratio

Petrogenicsource ratio

Pyrogenicsource ratio

Pyrogenicsource ratio

1900

1920

1940

1960

1980

20000 1 2 3 4 5 6

mz 192 / phenanthrene

Year

of D

epos

ition

0 1 2 3 4 5

1900

1920

1940

1960

1980

2000

mz 216 / pyrene

Ratios from Gustafsson & Gschwend (1997)

Assessment of Pyrogenic vs Petrogenic PAH inputs based on molecular parameters

1800

1820

1840

1860

1880

1900

1920

1940

1960

1980

20000 2 4 6 8 10 12 14 16

Phenanthrene

Retene

Flux (ng cm-2 yr-1)

Year

of D

epos

ition

0 10 20 30 40 50

30

Retene

Historical variations in PAH 14C

Lima et al in prep.

14C contents of individual PAH in environmental samples