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Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical...

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Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW.
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Page 1: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Biogeochemical cycling of dissolved organic C and nutrients

Figure by MIT OCW.

Page 2: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

1. Measured by HTCO orwet chemical oxidation

2. Surface values are 60-80µM Cdeep sea values are 40 µM C

3. Deep sea values are nearly constant(implies some tight feedback/control)

4. Global inventory is 680 GT C. Most Resides in the deep ocean!

The profile of [DOC]With depth in the ocean

Page 3: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Why 40 µM C? What processes set the global inventory of marine

organic carbon?

Figure removed due to copyrite restrictions. Source Unknown.

14C Production

Distribution amongC reservoirs

Geomagnetic Field Intensity

Cosmic Rays

Atm

Surf

Deep

Bio/Soils

14CO2

∆ 14C Cycle

SolarVariability

CaCO3 Seds

Deep

Surf

Figure by MIT OCW.

Page 4: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Pioneered by Pete WilliamsAt SIO.

Contamination is a big problem!!!

Does UV get it all ?

Pre AMS 1g C (1m3)Now about 1mg C (1L)

Page 5: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

DIC

DOC

Radiocarbon in DOC and DIC

DOC is depleted (older)than DIC at all depths

There is a source of newDOC in the surface ocean

The ∆∆14C between DICand DOC is not the sameat all depths (greater at theSurface)

CO2->DIC->POC->DOC

Page 6: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Radiocarbon in the Atlantic and Pacific Oceans

DIC 14C has the sameValue in the Atl and Pac

∆∆14C of DIC and DOCis about the same in thedeep Atl and Pac oceans

Deep ocean values areequal to a RC age of Several 1000�s years

Either there is a source of�old� DOC, or DOC lastsfor several ocean mixingcycles

Page 7: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Why is DOC old in surface water?

Page 8: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Why is DOC old in surface water?

Page 9: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Why is DOC old in surface water?

New DOC∆14C=DIC

Old

DO

C∆1

4 C =

DO

C(d

eep)

Page 10: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Why is DOC old in surface water?

New DOC∆14C=DIC

Old

DO

C∆1

4 C =

DO

C(d

eep)

Atlantic surface water

14Ccalc = -120 �14Cobs = -127 �

Pacific surface water

14Ccalc = -147 �14Cobs = -148 �

Page 11: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

What flux of carbon is needed to maintain themarine DOC reservoir?

Global inventory/residence time = annual flux

680 GT C/ 5000-6000 yr = 0.11-0.14 GT C/yr !!!

How does this compare with other C fluxes?

Page 12: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or
Page 13: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

What is the source of Marine DOC ?

Stable C isotopes

Marine C -21�

Terrestrial C

C3 plants -27�

C4 plants -15�

Page 14: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Hard problems in oceanography- what is DOC

and why is it so old??

DOC = humic substances

Page 15: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Sampling DOC is hard to do�DOC= 1mg/L C Salt = 35g/L

Separation based on size

1 nm pore @ 1 kD

Selects for HMW fraction

about 30-35% TOC

Membrane effects whatIs collected

Some salts collected too!

Cross Flow Filtration

High Pressure

Low Pressure

Figure by MIT OCW.

Page 16: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

13C Nuclear Magnetic Resonance Spectrumof high molecular weight dissolved organic matter

C/N = 15+3

Page 17: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

13C Nuclear Magnetic Resonance Spectrumof high molecular weight dissolved organic matter

COOHCONH(10%)

OCO(12%)

HCOH(55%)

CHx

(10%)

Page 18: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

1HNMR of high molecular weight DOC

OCO

HCOH

CHx

CH3CO-

aromatic

Page 19: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

HMWDOC, what could it be?

From our knowledge of cell biochemicals�

Proteins C/N = 4, CHx(O):CON = 3:1

Carbohydrates C only ? OCO:HCOH 1:5

Lipids C only CHxCOOHCHxCOH

��..looks to be mostly (50-70%) carbohydrate !

Page 20: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

280 µM C

80-100 µM C

Page 21: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Relative abundance of major biochemcials in HMWDOC

Page 22: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

HMWDOC in freshwater and marine environments

Page 23: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

OO

O

hydrolysisH+

Polysaccharide Analysis

1

2

3

4

4

56

78

0Minutes

23

2 Fructose, Glucose3 Sucrose

Figure by MIT OCW.

Page 24: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Relative abundance of sugars in HMWDOC

Rel

ativ

e %

Page 25: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

HMWDOC monosaccharides in rivers,lakes, and seawater

BUT�..yields of sugars are only 5-15% HMWDOC

Locations of sampling:Eel RiverLake SuperiorNobska PondDelaware RiverMississippi River

Image removed due to copyright restrictions.

Page 26: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

1HNMR of high molecular weight DOC

OCO

HCOH

CHx

CH3CO-?

aromatic

Page 27: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

15N-NMR of HMWDOC. Is HMWDONfrom protiens or from amino sugars?

Amide (RCON)(90-100%)

Free amine (R-NH2)(0-10%)

amino sugars

O

CH3CONH

RC(O)NC(R)C(O)

Page 28: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Is a large fraction of HMWDOC and HMWDONfrom amino sugars or proteins?

amino sugarsproteins

O

O

CH3CONH

CH3CONH

X

RC(O)NC(R)C(O)

RC(NH2)COOH

(amino acids)

Page 29: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Is a large fraction of HMWDOC and HMWDONfrom amino sugars?

CH3COOH

O

O

CH3CONH

HNH

H+

X X

Page 30: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

What is the �lipid� in HMWDOC?

Lipid

CH3(CH2)nCOH

CH3(CH2)nCOOH

OCO

HCOH

CHx

CH3CON

Deoxy sugars

OCH3

OH2COH

Page 31: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

There are really �two� types of lipid in HMWDOC

CH3COOH

CHx

Page 32: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

The effect of periodate on HMWDOCIs the lipid really lipid?

Lipid

RCOH

OCO

HCOH

CHx

CH3CON No Reaction

Deoxy sugarsCH3

O CH3COOH

Page 33: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

Periodate oxidation of HMWDOC

NaIO4

∆ 80oC

Page 34: Biogeochemical cycling of dissolved organic C and nutrients · 2020-01-04 · Biogeochemical cycling of dissolved organic C and nutrients Figure by MIT OCW. 1. Measured by HTCO or

HMWDOC composition summary

Direct chemical analyses show that HMWDOC is 50-70%carbohydrate, 5-6% acetamide, and 5-6%�lipid�

Chemical hydrolyses techniques show HMWDOC to be 15% carbohydrate, 3-5% protein, and <1% lipid

Indirect chemical analyses show that an additional 25%Is amino sugars, and 25% is deoxysugars. However,There is no direct confirmation of this.

A good portion of >25% remains uncharcterized.Much more at the molecular level.


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