6.7-6.9

Question 1

What are the factors that lead to the seasonal variation of CO2 concentrations in the atmosphere?

Answer 1

• [CO2] = ↑ in winter bc…dead plant matter decomposes
• [CO2] = ↓ in summer bc…CO2 is taken up by photosynthesis

Question 2

Which human activities contribute to the steady increase in average atmospheric CO2 concentrations?

Answer 2

• Fossil fuel consumption, cement production, deforestation
• 8.0 Gt C/year of CO2 = emitted from fossils/land use changes (mainly deforestation)

Question 3

What are the major pools of carbon in the global carbon cycle and processes that move carbon from one pool to another?

Answer 3

• Major pools = carbon in air, soil, biomass and oceans
• Drivers of exchange b/w air and biosphere = cycles of respiration/photosynthesis, absorption/outgassing from oceans

Question 4

How does the ocean take up CO2? Why doesn’t the ocean serve as an infinite sink for CO2?

Answer 4

• Because the ocean water is alkaline and CO2 acidic = CO2 reservoir
• Not an infinite sink bc only top 75 m = exchanges w/ atmosphere and as CO2 is absorbed, it is uses up available alkalinity by forming carbonate ions = slowing CO2 uptake

Question 5

What are some factors that make it hard to estimate and predict the amount of carbon stored in the biosphere?

Answer 5

• Storage could ↑ from fertilizing (↑ CO2 in atmosphere = (↑ plant growth)
• BUT nitrogen, phosphorous, and water may be limiting resources for ↑ biomass production
• ↑ temps = ↑ rates of respiration = > rate of photosynthesis  could create net carbon loss
• If global warming rapidly shifts climates, could cause major forest die-offs

Question 6

preindustrial [CO2]=

Answer 6

280 ppm

Question 7

current [CO2] =

Answer 7

390 ppm

Question 8

Reservoir

Answer 8

region of environment that holds significant maount of material
- Physically or chemically separated from other reservoirs

Question 9

Flows

Answer 9

how much material is transferred from 1 reservoir/time

Question 10

Steady state

Answer 10

inflows = outflows

Question 11

Residence times

Answer 11

average length of time material spends in reservoir
- Ratio of: reservoir size/inflow or outflow rate

Question 12

How do you determine the mass of material in a reservoir?

Answer 12

Mass = (concentration of material obtained in sample)*(size of reservoir)

Question 13

Methane

Answer 13

main constituent of natural gas deposits

Question 14

methane production

Answer 14

Produced by microbes living in anaerobic conditions

Question 15

Aerobic microbes use CH4 as energy source =

Answer 15

↓ CH4 in atmosphere

Question 15

Microbial sources:

Answer 15

forestomaches of ruminant animals, termite colonies, wetlands, rice paddies, manure piles, landfills

Question 16

Reduction of methane =

Answer 16

Δs to rice cultivation, collection of CH4 from landfills, better manure management

Question 17

does co2 or ch4 release have a greater impact for climate change?

Answer 17

CH4

Question 18

ch4 and permafrost feedback loop

Answer 18

• ↑ CH4 from climate change = ↑ released from seafloor and permafrost
• As ↑ water temp = ↑ CH4 release

Question 19

Where do methane deposits come from?

Answer 19

Produced by microbes living in anaerobic conditions
- Microbial sources: forestomaches of ruminant animals, termite colonies, wetlands, rice paddies, manure piles, landfills

Question 20

What are some natural processes that remove methane from the atmosphere?

Answer 20

• Oxidation w/in troposphere by OH (hydroxyl radical)
• Aerobic microbes use CH4 as energy source = ↓ CH4 in atmosphere

Question 21

What is the main process that leads to the release of N2O to the atmosphere?

Answer 21

Denitrification- bacteria converts nitrate in soil/water –> N2 and N2O

Question 22

What is the main source of CFCs?

Answer 22

Refrigerants (or air conditioners)

Question 23

Nitrification

Answer 23

microbial process reduce nitrogen (ammonia)  nitrite/nitrate

Question 24

Denitrification

Answer 24

bacteria converts nitrate in soil/water –> N2 and N2O

Question 25

what causes increased n2o?

Answer 25

↑ fertilizers = ↑ N2O

Question 26

what are CFCS?

Answer 26

Chlorofluorocarbons = Synthetic gases

Question 27

What is the main source of CFCs?

Answer 27

Refrigerants (or air conditioners)