lec 11: Greenhouse Gases

Question 1

what are the 3 main natural greenhouse gases?

Answer 1

1. Carbon dioxide
2. methane
3. water vapor

Question 2

How do 2 atoms gas molecules move? Name 2 of them.

Answer 2

They move by stretching
Oxygen
Nitrogen

Question 3

How do >2 atoms gas molecules move?

Answer 3

stretching and bending

Question 4

Why is it that some >2 atom gases molecules interact with infrared radiation and some don’t ?

Answer 4

For some molecules, the rate of the bending movement can fall into the wavelength range of infrared radiation

If they are interacting, energy is being absorbed!

Question 5

How does infrared radiation and bending molecules interact?

Answer 5

infrared radiation causes bending vibrations to move more vigorously, they then absorb more kinetic energy, which they will later release when slowing down

(some to space = lost, some to earth = heat)

Question 6

What is a chemoautotroph?

Answer 6

life that uses inorganic substances as electron donors or acceptors (exclude either carbon, oxygen or both)

Question 7

what are 2 reactions where molecules other than carbon are the electron donor (O2 is the electron acceptor)?

Answer 7

1. Nitrification
2. sulphur oxidation (bacteria)

Question 8

what are 4 Reactions where molecules other than oxygen are the electron acceptor?

Answer 8

1. Denitrification
2. Sulphate reduction
3. Iron reduction
4. methanogenesis

Question 9

what are the 2 ways to compare greenhouse gases?

Answer 9

1. Residence time
2. global warming potential

Question 10

What is residence time?

Answer 10

• the amount of time a greenhouse gas remains in the atmosphere reservoir

Question 11

What is the global warming potential? (GWP)

Answer 11

• measure of the contribution of a gas on global warming, using CO2 as a standard
• For a given time period: how much infrared energy 1 ton of gas will absorb compared to 1 ton of CO2
  
  • often measured out of 100 years

Question 12

What are the 3 most impactful gases based on GWP, residence time, current atmospheric concentration and human influence

Answer 12

1. CO2
2. methane
3. nitrous oxide

Question 13

what is the natural source of methane?

Answer 13

-methanogens
- bacterial species
- found in areas lacking oxygen
- animals which ferment their food during digestion

Question 14

What are the anthropocentric sources of methane?

Answer 14

• agriculture
  
  • animal industry → cows
  • crops (rice in particular)
• energy
  
  • natural gas is mainly methane
  • processing of petroleum releases methane

Question 15

what is the biggest contributor to methane production and why?

Answer 15

the cattle industry because of
1. methanogenesis, which takes place during the digestion of foods in ruminant mammals (cows)
2. the huge biomass of cows globally results in a high impact

Question 16

what is permafrost?

Answer 16

• Soil water which has remained frozen for a minimum of 2 continuous years

Question 17

what is the positive feedback loop between melting permafrost and increasing atmospheric temperature

Answer 17

melting permafrost = more atmospheric GHG = increasing temperatures = melting permafrost

Question 18

what is the natural source of nitrous oxide?

Answer 18

it is part of the nitrogen cycle
- produced by bacteria in the soil
- lightning breaking N3 bonds in the atmosphere

Question 19

What are the anthropocentric sources of nitrous oxide?

Answer 19

• anthropocentric nitrious oxide
  
  • produced as a byproduct of agriculture
    
    • nitrogen fertilizer used for crops feed bacteria, which produce more nitrous oxide
  • lesser contributor to greenhouse gases, but increasing

Question 20

How is nitrous oxide removed from the atmosphere

Answer 20

• removed from the atmosphere by bacteria, breakdown by UV radiation

Question 21

What is the equation for residence time?

Answer 21

R.T = Excess particular gaz / net particular gas sink

Question 22

What is the equation for energy transfer efficiency?