Carbon Dioxide and Carbonate system

Carbon cycle - Why is it important?

1. Regulates temperature of the planet2. Important for life in the ocean 3. Regulates the pH of water

How much CO2 can you sink in the ocean?

Process that control CO2 absorption in the ocean

Chemical

Biological

Physical

Carbon Cycle

Carbon Cycle

CO2

Temperature

CO2 changes in the last 300 yr

CO2 changes in the last 50 yr

OceansBiosphere

Rock Weathering

Greenhouse effect

• Caused by gases such as CO2 and water vapor that allow sunlight to pass through but trap heat energy (infrared) before it is reradiated back in space!

• Greenhouses gasses are increasing due to human activities – increasing the average global temperature and causing global worming;

• How and what are the effects?

The Carbonate System

2 2 2 2

23 3

( ) ( )

( ) 2 ( )

H O CO gas H CO aq

H HCO aq H CO aq

2 23 3( ) ( )CaCO s Ca aq CO

from dissolution of Calcium Carbonate

from dissolved CO2 gas

sources of inorganic carbon

Biology and Physics participate in the equilibrium of the carbonate system

NOTE:

10log [ ]pH H

CO2 in the ocean

Carbonic Acid

2 2 2 3 3( )H O CO gas H CO H HCO

Bicarbonate Ion

Carbon Dioxide and Carbonate system

23 32HCO H CO

Carbonate

High pH

2 2 2 3 3( )H O CO gas H CO H HCO

Carbon Dioxide and Carbonate system

23 32HCO H CO

Low pH-

+

Distribution of Carbon species in water

323

[ ]

[ ]

HCO

CO

+ 323

[ ]

[ ]

HCO

CO

-

Control of pH10log [ ]pH H

23 3( ) ( )HCO aq H CO aq

very rapid reaction in seawater

at equilibrium

23

3

[ ][ ]

[ ]

H COK

HCO

Equilibrium constant

323

[ ][ ]

[ ]

K HCOH

CO

hydrogen ion concentration

323

[ ]

[ ]

HCO

CO

+ 323

[ ]

[ ]

HCO

CO

-

23

3

[ ][ ]

[ ]

H COK

HCO

hydrogen ion concentration

Concept of Alkalinity

3 2 2

23 2 2

( ) ( )

( ) 2 ( )

HCO aq H H O CO gas

CO aq H H O CO gas

23 3[ ] 2[ ]A HCO CO

Why is the pH of seawater close to neutral?

10log [ ]pH H

seawaterpH=7.5-8.5

Average is 8.1