Terrestrial Biogeochemistry The study of the biological, geological and chemical factors that control the distribution and abundance of elements on land

Terrestrial BiogeochemistryTerrestrial Biogeochemistry

The study of the biological, geological and chemical factors that The study of the biological, geological and chemical factors that control the distribution and abundance of elements on landcontrol the distribution and abundance of elements on land

Introduction - Chapter 1Introduction - Chapter 1

Studying the earth system is complicatedStudying the earth system is complicated--large spatial and temporal scales--large spatial and temporal scales--feedback effects--feedback effects--no true replication--no true replication

……but we do the best we canbut we do the best we can--plot-scale experimental work--plot-scale experimental work--regional scale studies--regional scale studies--modeling to extrapolate in space and time--modeling to extrapolate in space and time--remote sensing of major earth processes--remote sensing of major earth processes

Fluctuations are the KEY to most element cycles

Introduction - Chapter 1Introduction - Chapter 1

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Source: Luthi et al. (2008) Nature 453:379-382

Source: Pearson and Palmer (2000). Nature 406:695-699

QUIZQUIZ

1.1. What links obesity in America to annual fish kills in the Gulf of Mexico?What links obesity in America to annual fish kills in the Gulf of Mexico?

2.2. What do the deserts of Asia and the wet tropical forests of Hawaii share What do the deserts of Asia and the wet tropical forests of Hawaii share in common?in common?

3.3. If you wanted to reduce the concentration CO2 in the EarthIf you wanted to reduce the concentration CO2 in the Earth’’s s atmosphere, what the best long-term storage reservoir?atmosphere, what the best long-term storage reservoir?

Six elements constitute 95% of mass of biosphere (i.e. Six elements constitute 95% of mass of biosphere (i.e. living organisms)living organisms)

--C, H, N, O, P and S--C, H, N, O, P and S

20 Other elements are critical to life20 Other elements are critical to life

All elements have mass < iodine (atomic mass 53)All elements have mass < iodine (atomic mass 53)

--Life is driven by --Life is driven by ““lightlight”” elements elements

Origins - Chapter 2Origins - Chapter 2

Origins of the ElementsOrigins of the Elements

What is the distribution of elements in our solar system?What is the distribution of elements in our solar system?

(1) Except for Li, Be, and B, light elements (atomic number <30) are (1) Except for Li, Be, and B, light elements (atomic number <30) are more abundant than heavy elements;more abundant than heavy elements;

(2) Elements with even AN are more abundant than odd AM(2) Elements with even AN are more abundant than odd AM (Figure 2.1)(Figure 2.1)

How did these elements form?How did these elements form?““Big BangBig Bang”” ~13.7 Billion Years Ago (BYA) ~13.7 Billion Years Ago (BYA)

Fusion of Fusion of ““quarksquarks”” into protons ( into protons (11H) and neutronsH) and neutrons

And…fusion of protons and neutrons to form simple atoms: And…fusion of protons and neutrons to form simple atoms: 22H, H, 44He, He,


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Astrophysical Properties:Based on spectral emission of stars including our sun.

Origins of the ElementsOrigins of the Elements

What is the distribution of elements in our solar system?What is the distribution of elements in our solar system?

(1) Except for Li, Be, and B, light elements (atomic number <30) are (1) Except for Li, Be, and B, light elements (atomic number <30) are more abundant than heavy elements;more abundant than heavy elements;

(2) Elements with even AN are more abundant than odd AM(2) Elements with even AN are more abundant than odd AM (Figure 2.1)(Figure 2.1)

How did these elements form?How did these elements form?““Big BangBig Bang”” ~13.7 Billion Years Ago (BYA) ~13.7 Billion Years Ago (BYA)

Fusion of Fusion of ““quarksquarks”” into protons ( into protons (11H) and neutronsH) and neutrons

And…fusion of protons and neutrons to form simple atoms: And…fusion of protons and neutrons to form simple atoms: 22H, H, 44He, He,


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Astrophysical Properties:Based on spectral emission of stars including our sun.

But…temperature and pressure But…temperature and pressure ↓ declined rapidly↓ declined rapidly

……formation of heavier elements could not occurformation of heavier elements could not occur

…………until the formation of stars (>1 BY)until the formation of stars (>1 BY)

Stars: whirling clouds of gas and dustStars: whirling clouds of gas and dust

Core: Hydrogen Core: Hydrogen ““burningburning”” 22H + H + 22H H → → 44HeHe

As star ages, H is consumed, star collapses inward under own As star ages, H is consumed, star collapses inward under own gravity…gravity…


Collapse Collapse ↑ core temperature and pressure↑ core temperature and pressureResulting in He burning…which generates carbon!Resulting in He burning…which generates carbon!

44He + He + 44He ↔ He ↔ 88Be Be (unstable, rapid decay)(unstable, rapid decay)88Be + Be + 44He → He → 1212CC

But also…But also…44He + He + 1212C → C → 1616O OXYGEN!O OXYGEN!

&&1212C + C + 1212 C → C → 2424Mg MAGNESIUM!Mg MAGNESIUM!

Which can decay to…Which can decay to…2424Mg → Mg → 2020Ne + Ne + 44He (alpha particle)He (alpha particle)


Planetary Planetary ““formationformation”” model explains elements up to AM model explains elements up to AM

of Fe (= 55.9)of Fe (= 55.9)

… … but a star core dominated by Fe won’t burn, causing a but a star core dominated by Fe won’t burn, causing a

supernova (catastrophic collapse and explosion)supernova (catastrophic collapse and explosion)

Elements w/AM > Fe formed by capture of successive Elements w/AM > Fe formed by capture of successive

neutrons by Fe which requires LOTS of energyneutrons by Fe which requires LOTS of energy


National Radio Astronomy Observatory produced National Radio Astronomy Observatory produced this series of images showing SN1993J as it expandsthis series of images showing SN1993J as it expands to a diameter of 1/10th of a light year in 18 months to a diameter of 1/10th of a light year in 18 months

Collectively this model explains:Collectively this model explains:

1.1. Logarithmic Logarithmic ↓ in abundance of elements after H and He (original building ↓ in abundance of elements after H and He (original building blocks)blocks)

--3 Phases--3 PhasesBig Bang (H, He)Big Bang (H, He)Core Burning (C-Fe)Core Burning (C-Fe)Supernova – Fusion (AM>Fe=56)Supernova – Fusion (AM>Fe=56)

2. 2. Even AM elements are more abundant than odd AM elementsEven AM elements are more abundant than odd AM elements-- Formation of all elements beyond Li is based on fusion of nuclei with even -- Formation of all elements beyond Li is based on fusion of nuclei with even number of atomic massnumber of atomic mass

--Odd AM elements formed by fission of heavier elements and they are less --Odd AM elements formed by fission of heavier elements and they are less stablestable

1616O + O + 1616O → O → 3232S → S → 3131P + P + 11HH


Why are Li, Be and B in such low cosmic abundance?Why are Li, Be and B in such low cosmic abundance?

Initial fusion reactions pass over nuclei of AM 5 and skip to elements with Initial fusion reactions pass over nuclei of AM 5 and skip to elements with even AM>8;even AM>8;

Li, B, Be are formed by spallation—fission of heavier elements that are hit Li, B, Be are formed by spallation—fission of heavier elements that are hit by cosmic rays in interstellar space!by cosmic rays in interstellar space!


Origin of the Solar System and the EarthOrigin of the Solar System and the Earth

Our galaxy is ~12.5 billion years oldOur galaxy is ~12.5 billion years old

Our solar system is ~4.6 billion yearsOur solar system is ~4.6 billion years

-- the remnants of a supernova;-- the remnants of a supernova;

-- all material is derived from -- all material is derived from ““planetesimalsplanetesimals”” formed by formed by the the coalescence of dust and small bodies;coalescence of dust and small bodies;

-- each planet is unique because it is derived from different -- each planet is unique because it is derived from different portions of the solar nebula.portions of the solar nebula.


MercuryMercury

Inner Planets Inner Planets SunSunMercuryMercuryVenusVenusEarthEarthMarsMars

‘‘hothot’’ portions of solar nebula portions of solar nebula

Outer Planets Outer Planets JupiterJupiterSaturnSaturnUranusUranusNeptuneNeptunePlutoPluto

‘‘coolcool’’ portions of solar nebula portions of solar nebula

““InnerInner”” planets formed in planets formed in ““hothot”” areas of solar nebula; areas of solar nebula; ““OuterOuter”” plants formed in plants formed in ““coolcool”” areas of the solar nebula. areas of the solar nebula.

MercuryMercury ( (““innerinner””) dominated by Fe and other elements formed at ) dominated by Fe and other elements formed at high temp; high bulk density 5.4g cmhigh temp; high bulk density 5.4g cm-3-3

VS.VS.

JupiterJupiter ( (““outerouter””) dominated H and He (BD = 1.25 g cm) dominated H and He (BD = 1.25 g cm-3-3) w/overall ) w/overall composition same as cosmic abundance of elementscomposition same as cosmic abundance of elements

EarthEarth ( (““innerinner””) dominated by silicate materials due to intermediate ) dominated by silicate materials due to intermediate temperatures (BD = 5.5 g cmtemperatures (BD = 5.5 g cm-3-3); low abundance of light elements ); low abundance of light elements relative to solar abundance.relative to solar abundance.


What is the elemental composition of the earth?What is the elemental composition of the earth?

--Analysis of total vs. crustal composition --Analysis of total vs. crustal composition suggests differentiationsuggests differentiation

Per

cent

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Homogenous accretion applies the principles of denisty separation. The heavy materials sink to the core during the hot period, and the lighter elements float to the surface. Then as the earth cools, the lighter elements can begin to solidify. This leads to the density separation of the earths distribution of elements.

Per

cent

What is the distribution of elements on the earth?What is the distribution of elements on the earth?--Analysis of crustal composition vs. total elemental composition --Analysis of crustal composition vs. total elemental composition suggests differentiation suggests differentiation (Figure 2.3)(Figure 2.3)

Theories:Theories:Homogenous AccretionHomogenous Accretion::

1. All elements arrived early in formation (~100MY);1. All elements arrived early in formation (~100MY);

2. NRG—collision of planetesimals and radioactive decay—melts 2. NRG—collision of planetesimals and radioactive decay—melts Fe, Ni etc…and form magma;Fe, Ni etc…and form magma;

3. Density separation of elements3. Density separation of elements- Heavy core, light crust;- Heavy core, light crust;

4. As earth cools lighter elements solidify on surface 4. As earth cools lighter elements solidify on surface (Figure 2.4)(Figure 2.4)


Heterogeneous AccretionHeterogeneous Accretion::

1. Planetesimals and other materials not consistent through earths 1. Planetesimals and other materials not consistent through earths formation.formation.

--Core constituents arrived earlier than mantle --Core constituents arrived earlier than mantle

2. Late arrival of light elements in carbonaceous chondrites2. Late arrival of light elements in carbonaceous chondrites

Which theory is correct? Well, not mutually exclusive… but late veneer of light Which theory is correct? Well, not mutually exclusive… but late veneer of light elements seems probableelements seems probable

2020Ne can provide some clues…Ne can provide some clues…

-Noble gas, no reaction w/crust -Noble gas, no reaction w/crust (…no transformation)(…no transformation)

-Too heavy to leave atmosphere -Too heavy to leave atmosphere (…no losses)(…no losses)

-Not product of radioactive decay -Not product of radioactive decay (…no/low rate of new input)(…no/low rate of new input)

……abundance of abundance of 2020Ne in atm. today Ne in atm. today ≈≈ abundance in solar cloud abundance in solar cloud


Assume other elements were delivered simultaneously, thenAssume other elements were delivered simultaneously, then

Mass of Element Mass of Element ZZ = = Qty of Qty of ZZ in Solar Cloud in Solar Cloud x x Qty Qty 2020Ne on EarthNe on Earth

on Earth on Earth Qty of Qty of 2020Ne in Solar CloudNe in Solar Cloud

Consider the Consider the 1414N:N:

Ratio of Ratio of 1414N/N/2020Ne in Solar Cloud = 0.91Ne in Solar Cloud = 0.91

Mass of Mass of 2020Ne on Earth = 6.5 x 10Ne on Earth = 6.5 x 101616gg

Predict:Predict: 5.9 x 105.9 x 101616g Ng N


Observe:Observe: 39 x 10 39 x 102020g Ng N

……suggesting a heterogeneous accumulation of N on Earth!suggesting a heterogeneous accumulation of N on Earth!

F Albarède Nature 461, 1227-1233 (2009) doi:10.1038/nature08477

A tentative chronology of the Earth’s accretion.

Chronometers shown in brown. Accretion of planetary material was interrupted by energetic electromagnetic radiation (T Tauri phase) sweeping across the disk within a few Myr of the isolation of the solar nebula. Runaway growth of planetesimals produces Mars-sized planetary embryos, which, collision after collision, form the planets with their modern masses. The last of these 'giant' collisions left material orbiting the Earth that later reassembled to form the Moon. The 182Hf–182W chronometer dates metal–silicate separation. The identical abundance of radiogenic 182W between the Earth and the Moon indicates that either the Moon formed after all the short-lived 182Hf had disappeared (>60 Myr) or, rather, the Moon-forming impact and terrestrial core segregation took place simultaneously 30 Myr after isolation of the solar nebula. Addition of a late veneer of chondritic material coming from beyond 2.5 au provides a strong explanation for the modern abundances of siderophile and volatile elements in the terrestrial mantle. This material also contained water and other volatile elements, which account for the origin of the terrestrial ocean. Such a model indicates that most of the terrestrial Pb and Xe was delivered by the asteroids that constituted the late veneer, and therefore that the young Pb–Pb and I–Xe ages of the Earth date, not the Earth, but events that affected the asteroids. It is suggested here that these events are those of the accretion to the Earth of the late veneer.

Origins of Atmosphere and OceansOrigins of Atmosphere and Oceans

AtmosphereAtmosphere::Carbonaceous chondrites major sources of C and NCarbonaceous chondrites major sources of C and N

0.5 – 3.6 % Carbon0.5 – 3.6 % Carbon0.01 – 0.28% Nitrogen0.01 – 0.28% Nitrogen

Comets likely sources of C,N, H, O and other volatilesComets likely sources of C,N, H, O and other volatiles

Meteors inputs in 1Meteors inputs in 1stst billion years accounts for earths mass billion years accounts for earths mass

Early Atmospheric CompositionEarly Atmospheric Composition--Most volatiles degassed from rocks delivered to mantle--Most volatiles degassed from rocks delivered to mantle--Volcanoes emit light elements --Volcanoes emit light elements degassing ongoing degassing ongoing--H--H22O, CHO, CH44, SO, SO22, HCl, CO, HCl, CO22, N, N22


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Recent input of meteors is too low to account for the earths mass over the last 5 billion years. Aging of craters on moon suggest a rapid slowing of meteor bombardament about 3.8 billion years ago.

OceansOceans::When Earth hot (>100 When Earth hot (>100 ooC) volatiles in atmosphere.C) volatiles in atmosphere.

As EarthAs Earth’’s surface cooled (<100 s surface cooled (<100 ooC)….water started to condense and form the C)….water started to condense and form the OCEANSOCEANS


……one one h e l lh e l l of a rainstorm… of a rainstorm…

Liquid water ever since 3.8 BYA.Liquid water ever since 3.8 BYA.

Atmospheric gases enter into primitive ocean (HenryAtmospheric gases enter into primitive ocean (Henry’’s Law):s Law):

COCO22 + H + H22O O ↔ H↔ H22COCO33 ↔ H ↔ H++ + HCO + HCO33--

HCl + HHCl + H22O ↔ HO ↔ H33OO++ + Cl + Cl--

SOSO22 + H + H22O ↔ HO ↔ H22SOSO33

Gas solubility Gas solubility early on atm. dominated by N early on atm. dominated by N22

COCO22 1.4 g/L1.4 g/L

HClHCl 700 g/L700 g/L VS.VS. NN22 0.018 g/L0.018 g/L

SOSO22 94.1 g/L94.1 g/L


Early composition of ocean is difficult to know…Early composition of ocean is difficult to know…

--substantial qty. of Cl--substantial qty. of Cl-- (like today) (like today)

--dissolution of CO--dissolution of CO22 & HCl produce acids and & HCl produce acids and ““weatherweather”” crust crust

releasing cations (Nareleasing cations (Na++, Mg, Mg2+2+, Ca, Ca2+2+))

--oceans accumulate cations until formation of precipitates--oceans accumulate cations until formation of precipitates

CaCOCaCO33 dominant marine sediment for BYs dominant marine sediment for BYs

……suggesting that Earthsuggesting that Earth’’s early oceans similar to that today.s early oceans similar to that today.

Adrien Finzi

Given that CaCO3 is a dominant formation in modern and ancient oceans (fossil records dating back to billions of years), the chemistry of earths primative ocean is like to be similar to that of todays ocean...

Origin of LifeOrigin of Life

1.1. Reduced atm Reduced atm abiotic synthesis of OC; abiotic synthesis of OC;

2.2. Carbonaceous chondrites contain simple Carbonaceous chondrites contain simple OC and AA;OC and AA;

3.3. Clay minerals—surface charge and Clay minerals—surface charge and repeating structure—repeating structure—““stringstring”” together together OC……RNA……proteins…abiotically;OC……RNA……proteins…abiotically;

4.4. Polarity of organics forms coacervates in Polarity of organics forms coacervates in HH220…simple membranes;0…simple membranes;

5.5. In lab, organic molecules self replicate…In lab, organic molecules self replicate…although replicating, metabolizing, although replicating, metabolizing, membrane bound structures not yet membrane bound structures not yet produced ……but given billions of years…produced ……but given billions of years…

6.6. Science 9 January 2009, Vol. 323. no. Science 9 January 2009, Vol. 323. no. 5911, pp. 198 – 199, DOI: 5911, pp. 198 – 199, DOI: 10.1126/science.323.5911.19810.1126/science.323.5911.198


Apparatus used in the originalApparatus used in the originalMiller (1957) experimentMiller (1957) experiment

Origin of Metabolic PathwaysOrigin of Metabolic Pathways

3.8 BY old rocks contain fossil bacteria…oldest known life…evolved in the sea3.8 BY old rocks contain fossil bacteria…oldest known life…evolved in the sea

Early heterotrophs…(todayEarly heterotrophs…(today’’s methanogens?)s methanogens?)CHCH33COOH COOH → → 2CO2CO22 + CH + CH44

(Acetate)(Acetate) (Methane)(Methane)

N is a key component of biochemistry yet little availability N (e.g. NON is a key component of biochemistry yet little availability N (e.g. NO33--) in ) in

seawaterseawater

Origin of NOrigin of N22 fixation 2.2-3.5 BYA fixation 2.2-3.5 BYANN22 + 8H + 8H++ + 8e + 8e-- + 16ATP → 2NH + 16ATP → 2NH33 + H + H22 + 16ADP + 16Pi + 16ADP + 16Pi

-- N≡N requires 226kcal/mol energy to break triple bond-- N≡N requires 226kcal/mol energy to break triple bond-- low solubility of N-- low solubility of N22 in H in H22OO

Today N fixation coupled to photosynthesis Today N fixation coupled to photosynthesis Cynaobacteria (marine) Cynaobacteria (marine) Symbiosis w/plants Symbiosis w/plants

(terrestrial)(terrestrial)


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These organisms are consuming simple organic compounds. However, early heterotrphy must have been quite limited given that these organisms were dependent on abiotic synthesis of these compounds.There must have been tremendous selective advantage to autotrohpy early in life given that this would be the way to produce large quantites of reduced carbon substrates for life.

...early heterotrophy inefficient given abiotic source of organic cmpds...early heterotrophy inefficient given abiotic source of organic cmpds

Strong selective pressure for autotrophy…Strong selective pressure for autotrophy…

11stst Photosynthesis S-based (lower NRG of reaction, but limited S in oceans) Photosynthesis S-based (lower NRG of reaction, but limited S in oceans)

COCO22 + 2H + 2H22S → CHS → CH220 + 2S + H0 + 2S + H2200

……probably soon thereafter, Oprobably soon thereafter, O22-based PS-based PS

COCO22 + H + H22O → CHO → CH220 + 00 + 022 + H + H2200


sunlightsunlight

sunlightsunlight

Isotopic evidence for Ps (Isotopic evidence for Ps (bothboth S based / O S based / O22 evolving) evolving)

- - 1313COCO22 less reactive than less reactive than 1212COCO22

- physical < biological discrimination, both present- physical < biological discrimination, both present


Standard for C = Standard for C = ““Pee DeePee Dee”” Belemnite, South Carolina Belemnite, South Carolina

- Carbonates less depleted in - Carbonates less depleted in 1313C, 0 – 2 C, 0 – 2 ‰‰

- Carbohydrates greatly depleted in - Carbohydrates greatly depleted in 1313C, ~20 C, ~20 ‰‰

((Overhead 2.6Overhead 2.6))


Evidence for Evidence for OO22 releasing releasing Ps only Ps only

1. Banded Iron Formations1. Banded Iron Formations 3.5 – 2.0 BYA3.5 – 2.0 BYA

-Fe-Fe2+2+ in sea in sea Fe Fe22OO33 & S& S2-2-……

- no free O- no free O2 2 in the atmospherein the atmosphere

2. Red Beds (transient atm. O2. Red Beds (transient atm. O22)) 2.0 - Present2.0 - Present

-FeS-FeS22 on land oxidized on land oxidized

-bands of Fe-bands of Fe22OO33 alternates w/other continental alternates w/other continental

elementselements

3. Accumulation in atm 3. Accumulation in atm

- Ps > O- Ps > O22 consumption consumption

(Figure 2.7)(Figure 2.7)

A banded iron formation from the 3.15 BY old Moories Group, Barberton Greenstone Belt, South Africa. Red layers represent the times when oxygen was available, gray layers were formed in anoxic circumstances.


Free OFree O22 in atmosphere fundamental change to earth in atmosphere fundamental change to earth

I.I. Oxidizing agent in atmosphere (e.g. OOxidizing agent in atmosphere (e.g. O33 in stratosphere and UV) in stratosphere and UV)

II.II. Rapid evolutionRapid evolution Eukaryotes diverge from prokaryotes ~2BYA (end of B.I.F.)Eukaryotes diverge from prokaryotes ~2BYA (end of B.I.F.) Respiration in mitochondria efficient metabolismRespiration in mitochondria efficient metabolism Ps now in specialized chloroplasts…more efficientPs now in specialized chloroplasts…more efficient

III.III. Evolution of new biochemical pathwaysEvolution of new biochemical pathways ““ChemoautotrophyChemoautotrophy”” (protons coupled to CO (protons coupled to CO22 reduction) reduction)

NitrificationNitrification 2NH 2NH44

++ + 3O + 3O22 → 2NO→ 2NO22-- + 2H + 2H220 + 4H0 + 4H++

2NO2NO22-- + O + O22 → 2NO → 2NO33

--


……evolution of aerobic N transformations allow evolution of anaerobic N evolution of aerobic N transformations allow evolution of anaerobic N transformations…transformations…

DenitrificationDenitrification: (anaerobic…microsites): (anaerobic…microsites)

5CH5CH22O + 4HO + 4H++ + 4NO + 4NO33-- → 2N→ 2N22 + 5CO + 5CO22 + 7H + 7H22OO

Documents

Terrestrial Biogeochemistry The study of the biological, geological and chemical factors that control the distribution and abundance of elements on land