Chimie h2co3
Transcript of Chimie h2co3
1
The Carbon Cycle
Tracking Carbon Through the Earth System
H2CO3
Organic Inorganic
CO2
diffusion
CO2+H2OàH2CO3
CO2 CO2
Short Term
Long Term
weath
ering
CH4
decomposition
weatheringH2CO3
photosynthesisrespiration
uplift
rock formation
volc
anis
m
H2CO3àH++HCO3-
sedimentation sedimentationdissolution
2
Inorganic Carbon ReservoirsGt = Gigaton
=109 metric tons;= 2679 x 109 pounds
Some More DefinitionsIonsAtoms or molecules having either more or less electrons (-) than protons (+)giving them a positive or negative electrical charge.
CationPositively charged ion, missing electrons (H+, Na+, Ca+2).
AnionNegatively charged ion, extra electrons (Cl-, CO3
-2)..
pH-log[H+], tells how acidic or basic a solution is.
AcidA solution with a high concentration of H+, pH < 7.
BaseA solution with a low concentration of H+, pH > 7.
Chemical equilibrium A steady state for a chemical reaction that can move in both directions.
DissociationMolecules breaking appart into ions when dissolved in water.
3
Some More DefinitionsSourceInflow into a reservoirSinkOutflow from a reservoirFluxInflow, outflow; source, sink
HCl
HCl
HClHCl
H+
Cl-
Cl-
Cl-
H+
H+
Acid Water
Acids in Water Solutions
4
Acid-Base Scale: pH = -log[H+]
Chemical Equations
H2CO3 H+ + HCO3-
productsreactants
H2O + CO2 H2CO3
5
Equations to Know
Carbonic acid production from carbon dioxideand water:
CO2 + H2O H2CO3
H2CO3
Organic Inorganic
CO2
diffusion
CO2+H2OàH2CO3
CO2 CO2
Short Term
Long Term
weath
ering
CH4
decomposition
weatheringH2CO3
photosynthesisrespiration
uplift
rock formation
volc
anis
m
H2CO3àH++HCO3-
sedimentation sedimentationdissolution
6
DiffusionCO
2 CO2
Diffusion
CO2 + H2O <-----> H2CO3
Carbonate Chemistry
1
Water
CO2 DiffusionAtmosphere - Ocean Equilibrium
7
What Happens When CO2Dissolves in Water?
Carbonic acid
CO2 + H2O H2CO3
H2CO3 H+ + HCO3-1 2H+ + CO3
-2
Bicarbonate ion
Hydrogenion
Carbonate ion
Summary
• Removes dissolved CO2 from ocean• Increases acidity of ocean• Allows for further diffusion of CO2 from atmos-
phere into ocean.
Carbonate Ion Formation H2CO3 H
+ + HCO3-2 2H+ + CO3
-2
Acid FormationCO2 + H2O H2CO3
DiffusionCO2(atmos) CO2(ocean)
8
H2CO3
Carbonate Weathering:CaCO3 + H2CO3 à Ca+2 + 2HCO3
-
Ca2+, SiO2, HCO3- to ocean
Silicate Weathering:CaSiO3 + 2H2CO3 à Ca2+ + 2HCO3
- + SiO2 + H2O
Weathering2
3 Carbonate Mineral Deposition
Calcium Carbonate precipitates in the OceanCa2+ + 2HCO3
-à CaCO3 + H2CO3by organisms that make shells & skeletal structure
Ca+2
CO3-2
Increases acidity of Ocean
In shallow ocean collectsin sediments limestone
In deep ocean is dissolved by more acidic waterDecreases acidity of Ocean
CaCO3
9
4
CaCO3
Long-term Inorganic Cycle
Sedimentary Rockup
lift
volc
anis
mBalance of the Inorganic Carbon Cycle
Carbonateweathering
Carbonateprecipitation
Buried CO3-2 returns to atmosphere
via solid Earth processes.
10
CO2+H2O --> H2CO3CaSiO3 +2H2CO3-->Ca2+ + 2HCO3
- + SiO2 + H2OCa2
+ + 2HCO3- --> CaCO3 + H2CO3
CaSiO3 + CO2 --> CaCO3 + SiO2
Atmospheric CO2 should go away in about a million years, but it has not. Why not?
Net: C goes fromatmos to ocean floor.
Togetherthese 3mechanismsremove CO2from atmos .
Silicate
weathering
Balance of the Inorganic Carbon Cycle
Carbonate-Silicate Cycle
Carbonate-Silicate weathering is “balanced” by Carbonate Metamorphism
CaCO3+ SiO2àCaSiO3 + CO2
11
Carbonate-silicate Cycle
Silicate Weathering Feedback
12
H2CO3
Organic Inorganic
CO2
diffusion
CO2+H2OàH2CO3
CO2 CO2
Short Term
Long Term
weath
ering
CH4
decomposition
weathering
H2CO3
photosynthesisrespiration
uplift
rock formation
volc
anis
m
H2CO3àH++HCO3-
sedimentation sedimentationdissolution
Inorganic Carbon Cycle ProcessesWhat causes local imbalance in
ocean-atmosphere CO2 flux?
• Photosynthesis: Where plants actively take up CO2, ocean uptake may dominate.
• Upwelling: “Old” water contains lots of CO2. Where up-welling occurs, CO2 release to the atmosphere may dominate.
• Precipitation of CaCO3: In the open ocean, some phytoplankton make shells. At the same time they do photosynthesis. For every one CO2 they produce by precipitation, they take up 4 CO2’s by photosynthesis (See Color Figure 7-8b), ocean uptake may dominate.
Answer: Variations in productivity and upwelling.
13
Ocean-Atmosphere CO2 Diffusion
Reservoir = Atmosphere
in in
outout
out
Inorganic Carbon Cycle
WeatheringSedimentationDiffusion
Short term
Long term
14
Earth’s Carbon Reservoirs
0.08 Gton/yr
~7Gton/yr
increase inflowby ~ 6%
Equations to Know
• Photosynthesis:CO2 + H2O à CH2O + O2
• Respiration:O2 + CH2O à CO2 + H2O
2CH2O àCO2 + CH4
• Carbonic acid production from carbon dioxideand water:CO2 + H2O ßà H2CO3