geochemical tracers l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Geochemical tracers PowerPoint Presentation
Download Presentation
Geochemical tracers

Loading in 2 Seconds...

play fullscreen
1 / 37

Geochemical tracers - PowerPoint PPT Presentation


  • 912 Views
  • Uploaded on

Geochemical tracers Tracers – talking more about theory than application. Geochemical tracers trace: Circulation Climate Environmental conditions Geochemical tracers are proxies for past environmental conditions (and trace changes): Signals in sediments or other substrates

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Geochemical tracers' - ostinmannual


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
geochemical tracers
Geochemical tracers
  • Tracers – talking more about theory than application.
  • Geochemical tracers trace:
    • Circulation
    • Climate
    • Environmental conditions
  • Geochemical tracers are proxies for past environmental conditions (and trace changes):
    • Signals in sediments or other substrates
    • Isotopes (composition of the sediments)
    • Trace metals (in fossils)
    • Organic compounds
the record of climate events and ocean change recorded chemically
The record of climate events and ocean change recorded chemically
  • The Tools: Tracers
    • Geochemical tracers…..
  • the application
    • How we really do it
    • what are the issues
how do we trace the movement of components in the ocean
How do we trace the movement of components in the ocean?
  • Nutrient controls on productivity.
    • they are trace-able…
  • With major components like carbon, how can we track the cycling of that?
  • How can we trace changes in important properties in the past?
the biological pump
The biological pump….

How do we know it changed in the past?

How do we trace carbon movement through the system?

the tools
The tools

Geochemical tracers!

Isotopes:

13C – circulation

18O – temperature

Organic matter:

TOC – productivity

Biomarkers – temperature (relative productivity)

Anthropogenic compounds - pollution tracers

Trace metals- Trace metal ratios in calcite (CaCO3)

Cd/Ca (phosphate), Ba/Ca (nutrients),

Mg/Ca and Sr/Ca –temperature

trace metal inclusions in caco 3
Trace metal inclusions in CaCO3

Trace metals that are of similar size and charge as Ca substitute into the matrix…..

interpretation is based on the simple principle that if there is more in the water there is more in the calcite

Empirically, we have found their chemistry is controlled by:

Cd/Ca (phosphate),

Ba/Ca (“productivity”)

Mg/Ca and Sr/Ca –temperature

caco 3 impurities are controlled by
CaCO3 impurities are controlled by:

Many environmental parameters (thermodynamics, kinetics, biology)

Temperature– inclusions are more common when temperatures are higher.

Nutrients – many trace metal concentrations mimic nutrient distributions

organic markers or molecular markers
Organic markers or “molecular markers”
  • Total organic carbon (TOC)

– productivity

  • Biomarkers (individual compounds)
    • Trace organisms
    • Different environments and conditions

– temperature (relative productivity)

biomarkers persist in the sediments and contain information about the presence of past organisms

EUCARYA

m

a

n

HO

a

n

i

m

a

l

s

R

p

l

a

n

t

s

f

l

a

g

e

l

l

a

t

e

s

f

u

n

g

i

m

i

c

r

o

s

p

o

r

i

d

i

a

c

i

l

i

a

t

e

s

s

l

i

m

e

m

o

l

d

s

d

i

p

l

o

m

o

n

a

d

s

BACTERIA

ARCHAEA

green sulfur

bacteria

S

u

l

f

o

l

o

b

u

s

D

e

s

u

l

f

u

r

o

c

o

c

c

u

s

T

h

e

r

m

o

f

i

l

u

m

OH

OH

g

r

a

m

p

o

s

i

t

i

v

e

s

T

h

e

r

m

o

p

r

o

t

e

u

s

P

y

r

o

b

a

c

u

l

u

m

OH

OH

Thermotoga

p

r

o

t

c

o

b

a

c

t

e

r

i

a

P

y

r

o

d

i

c

t

i

u

m

P

y

r

o

c

o

c

c

u

s

cyanobacteria

M

e

t

h

a

n

o

-

M

e

t

h

a

n

o

b

a

c

t

e

r

i

u

m

t

h

e

r

m

u

s

a

v

o

b

a

c

t

e

r

i

a

A

r

c

h

a

e

o

g

l

o

b

u

s

H

a

l

o

c

o

c

c

u

s

Thermocrinis

1

2

H

a

l

o

b

a

c

t

e

r

i

u

m

3

M

e

t

h

a

n

o

p

l

a

n

u

s

Aquifex

4

M

e

t

h

a

n

o

p

y

r

u

s

M

e

t

h

a

n

o

s

p

i

r

i

l

l

u

m

M

e

t

h

a

n

o

c

o

c

c

u

s

1

j

a

n

n

a

s

c

h

i

i

M

e

t

h

a

n

o

s

a

r

c

i

n

a

>2.7 Ga

2

i

g

n

e

u

s

3

t

h

e

r

m

o

l

i

t

h

o

t

r

o

p

h

i

c

u

s

4

v

a

n

n

i

e

l

l

i

i

O

O

>2.7 Ga

OH

Biomarkers persist in the sediments and contain information about the presence of past organisms
slide11

C29

C28

C30

C30

Algal Steroids

  • Encode a variety of age-diagnostic signatures –
  • C-isotopes + steroids from algae & plants
    • chlorophyceans
    • diatoms
    • chrysophytes
    • dinoflagellates

‘geo’

‘bio’

alkenones as a tracer for sea surface temperature
Alkenones as a tracer for sea surface temperature

Alkenones are made only by Prymnesiophytes…

Alkenones record SST….

in their saturation levels

alkenones record information about climate
Alkenones record information about climate

The ratio of alkenones in a sample records past temperature similar to foraminifera

Southwest Pacific ~30,000 yr record

geochemical tracers14
Geochemical tracers

Two isotopes of concern:

Oxygen isotopes:

18O

Carbon isotopes

13C

geochemical tracers15
Geochemical tracers

Oxygen is:

16O=99.759%

17O=0.037%

18O=0.204%

notation is simply the ratio of 16:18 in the sample relative to a standard …..

del notation
“del” notation

A= (RA -1) x1000

RSt

which is the same as (18/16O)CaCO3sample –1) x1000

(18/16O)CaCO3 std

The result is we use “per mil” ‰ as our units

and we always speak about the data in reference to: the isotope of interest

the record of 18 o in the sediment record

Emerson and Hedges 2008

The record of  18O in the sediment record

The distillation is controlled by temperature salinity and ice volume.

The record is primarily a a function of temperature and ice volume

geochemical tracer carbon isotopes
Geochemical tracer: carbon isotopes

Carbon isotopes

12C=98.89%

13C=1.11%

14C=small and variable

fractionation of carbon is primarily biologically mediated23
Fractionation of carbon is primarily biologically mediated

Plants discriminate against 13C during photosynthesis.

The the ultimate 13C amount varies with plant type and substrate.

Libes chapt. 29

fractionation of carbon is primarily biologically mediated24
Fractionation of carbon is primarily biologically mediated

Plants discriminate against 13C during photosynthesis.

The the ultimate 13C amount varies with plant type and substrate.

Libes chapt. 29

the biological pump moves organic carbon
The biological pump moves organic carbon

The biological pump moves organic matter with it’s depleted isotopic signal from the surface ocean to the deep water masses…..

the conveyor belt circulation
The conveyor belt circulation

And thermohaline circulation moves CO2 through the system…

controls on the fractionation of 13 c

Water downwells:

DIC enriched

Low nutrients

High O2

Controls on the fractionation of 13C

13C

13C

12C

13C

13C

12C

12C

13C

12C

13C

13C

DIC

(in Water) more depleted with increasing age

13C

12C

12C

12C

12C

12C

Porewaters very sensitive to remineralization can be very depleted in 13C

12C

12C

12C

12C

12C

12C

how do we use these tracers
How do we use these tracers?

Evidence for the effects of… Short term perturbations (that we can verify other ways)

dissolved inorganic carbon change
Dissolved inorganic carbon change
  • DIC change in the ocean is due to increasing CO2 in the atmosphere
  • How can you trace increasing CO2 input when the ocean is full of CO2 ?

Find another complimentary tracer:

CFC: cloro-flouro-carbons

anthropogenic gases
Anthropogenic gases

Tracers with a known history…..

anthropogenic co 2
Anthropogenic CO2

This is calculated via a proxy. (13C or CFC’s) using 13C we can also trace inputs directly in the DIC…..

13 c can trace fossil fuel input
13C can trace Fossil fuel input
  • Fossil fuels are organic molecules
  • They are derived from compounds that were originally produced by photosynthetic organisms……
  • Therefore they have a depleted 13C signal (of about -20 to -30 ‰)

We can use this to measure the change in  CO2 directly. And on long time scales.