1. Environmental Chemistry

2. Origins Create the universe Create the elements Create the Earth
Form the atmosphere and oceans

3. Carbonate-silicate cycle
Timescale = 105 – 107 yrs
J. F. Kasting, Science Spectra, 1995

4. Feedback on CO2
Figure 09-11
How to Build a Habitable Planet Copyright © Princeton University Press 2012

5. Historical CO2 record
from Berner, Science, 1997

7. Solar output over time Solar output has increased by ~30% Figure 09-09
How to Build a Habitable Planet Copyright © Princeton University Press 2012

8. What about oxygen?

9. Oxidation states of elements
Figure 15-02
How to Build a Habitable Planet Copyright © Princeton University Press 2012

10. Step 1: Autotrophs E.g., Purple sulfur bacteria
6 CO2 + 6 H2S + light  C6H12O6 + 6 S
Uses energy from light
Oxidizes S and reduces C

11. Respiration Metabolizes glucose to produce ATP, CO2, and water
Anaerobic respiration (no O2) produces 2 ATP per glucose
C6H12O6  2 CH3CH2OH + 2 CO2
2ADP 2ATP

12. Step 2: Oxygenic Photosynthesis
Uses solar energy to split water and form organic compounds
O2 is a by-product

13. Step 3: Aerobic respiration
Uses free O2 to oxidize organic matter
Generates 36 ATPs
Provides enough energy for complex organisms

14. Oxygen is consumed by reactions with reduced Fe and S from lithosphere

15. Banded iron formations

16. “Biogeochemical cycle modelling indicates that prolonged super- greenhouse conditions and effective nutrient input to the ocean after the glaciation lead to high levels of primary productivity and burial of organic carbon. This causes an abrupt jump of oxygen levels within ∼104yr after the glaciation and an extensive oxygen overshoot to the present atmospheric level. The overshoot persists for ∼108yr because net consumption of oxygen in the atmosphere–ocean system is inefficient. We show that the post-glacial jump of oxygen levels occurred in biologically short timescale, which may have stimulated the ecological shift and/or biological innovations toward the prosperity of oxygen-dependent life.”

18. Evolution of life

19. Coevolution of CO2 and O2

20. Carbon cycle
Cycle includes flows of carbon from photosynthesis and respiration as well as Ca-Si cycling

21. Nitrogen Cycle
Processes