Origins of the Elements

From: Jacobson

Production of Heavier Elements

S O O

O He C

C He Be

Be He He

3216

168

168

168

42

126

126

42

84

84

42

42

Cosmic Composition of Elements

From: Jacobson

Composition of the Earth

• 93% - iron, oxygen, silicon, and magnesium

• 6.5% - nickel, sulfur, calcium, and aluminum

• 0.5% - 84 other elements

Composition of the Earth

• Core – iron and nickel

• Mantle – iron, magnesium, silicon

• Crust – oxygen, silicon

• Atmosphere – nitrogen, oxygen

• Elements of life – carbon, hydrogen, oxygen, nitrogen, phosphorous, sulfur

Elements of Life

• Carbon – structure, energy storage

• Hydrogen – water, electron transport

• Oxygen – aerobic respiration, water

• Nitrogen – amino acids, nitrogenous bases

• Phosphorus – ATP

• Sulfur – amino acids

• Others (Fe, Mg) – enzyme cofactors

The Water Cycle

From: Schlesinger

Potential Human Influence on theWater Cycle

• Restricted run-off

• Groundwater depletion

• Reduction in ice-pack

• Climate (increased evaporation, increased precipitation, increased run-off, sea level rise)

Calculating Lifetime

• If we assume that reservoirs are in steady state, the lifetime, τ, is the quantity in the reservoir divided by the sum of all sinks.

• The average τ of water in the atmosphere:

days6.9yr

days365

yrkm496000

13000km1-3

3

x

Chemical cycle diagrams are only for equilibrium conditions

sinkssourcesdt

dm

From: Jacob

sinkssourcesdt

dm

)1(S

)0()( - S ktkt ek

emtmkmdt

dm

Pre-industrial Carbon Cycle

From: Jacob

The Human InfluencedCarbon Cycle

From: http://dilu.bol.ucla.edu/home.html

Increase of Atmospheric CH4

From: http://www.ipcc.ch/present/graphics.htm

Increase of Atmospheric CO2

From: http://www.ipcc.ch/present/graphics.htm

created by Robert A. Rohdefrom NOAA published data

The Missing Carbon Sink

• Not all the ‘extra’ carbon emitted to the atmosphere remains there:

• Sources: fossil fuel and tropical forest burning = (6.0 + 1.6) Pg yr-1

• Increase in atmosphere = 4.0 Pg yr-1

• Missing sink = 3.6 Pg yr-1

• Possible sinks: ocean and terrestrial biosphere.

Atmosphere/OceanCarbon Exchange

• CO2 partitions into water according to Henry’s Law:H = 3x10-2 M/atm

• The ocean’s buffer system:

pKa1 = 6.1; pKa2 = 9.2The ocean’s pH is 8.2

)(3

)3()3(

)()3()(2)2(

)2()2(

HCOHCO

HHCOOHCO

COCO

aqaqaq

aqaqlaq

aqg

Effects of Rising CO2 onOcean Storage

• However, complete ocean mixing can take hundreds of years.

• Is ocean mixing the only way carbon is mixed into the ocean? – No, it is assisted by a biological pump.

The Ocean’s Biological Pump

From: http://calspace.ucsd.edu/virtualmuseum/images/OceansBiologicalPump.html

Effects of Rising CO2 onOcean Storage

From: Jacob

Biosphere/Atmosphere Exchange of Carbon

• Source – burning, decay, and respiration

• Sink – photosynthesis, dissolution into ocean

2222 OO)CH(OHCO nnn nh

OHCOOO)CH( 2222 nnnn

The Nitrogen Cycle

From: Jacob

Lifetime of N2 in the Atmosphere

• Atmospheric reservoir = 3.9 x 109 Tg

• Sinks = (80+160+80+30+20) Tg yr-1

• Lifetime (τ) = 1.0 x 107 yr (10 millions yrs)

• However, the N2 cycle is heavily disturbed by human activities.

Active Nitrogen

• Nitrogen Fixation:

bacteria

lightning, combustion

• Nitrification:

• Denitrification:

NON

NHN

2

32

)(2)2(32 ON ,NNO ,NO gg

-3

-2)(34 NO ,NO ,NHNH g

Increase of Atmospheric N2O

From: http://www.ipcc.ch/present/graphics.htm

Global Phosphorus Cycle

From: Schlesinger

What Controls Atmospheric O2?

• Remember the reactions:– These control carbon in the atmosphere, but

do they control oxygen?

photosynthesis

respiration, decayOHCOOO)CH( 2222 nnnn

2222 OO)CH(OHCO nnn nh

The Coupled Carbon/Oxygen Cycle

From: Jacob

What Controls Atmospheric O2?

• What if photosynthesis stopped?– 0.8% decrease of O2

– 470% increase of CO2

• What if respiration and decay stopped?– 0.1% increase of O2

– 100% decrease of CO2

What Controls Atmospheric O2?

• Sources (photosynthesis, anaerobic metabolism)

• Sinks (sedimentary rock weathering)

OH23CO15FeS4OCH15SOH8OFe2

OO)CH(OHCO

222bacteria

24232

2222

nnn nh

-2432222

2222

8SOH16OFe215OOH8FeS4

OHCOOOCH

What Controls Atmospheric O2?

From: Jacob