carbon cycle

Question 1

Residence time

Answer 1

At a steady state, the average time carbon spend in the reservoir is called residence time
of carbon.
[CO2]/(CO2/days) = Concentration/ flux or uptake

Question 2

Flux in carbon

Answer 2

The movement of any material from one place to another is called a flux and we typically
think of a carbon flux as a transfer of carbon from one pool to another.

(e.g. g cm-2 s-1 or kg km2 yr-1
).

Question 3

carbon flux

Answer 3

Flux is represented here as Peta
grams per year (Pg/year)

Question 4

processes that assimilate carbon in environment

Answer 4

photosynthesis(123) that stores the carbon into autotrophs

dissolution (92.3)
CO₂ dissolves in seawater and is either stored as dissolved inorganic carbon or used by marine organisms for photosynthesis.

Question 5

processes that release the stored carbon

Answer 5

respiration (50pg/yr)

respiration soil(70pg/yr)
(released by decomposition of organic matter in the soil, as well as from combustion processes such as wildfires.)

emission (90pg/yr)
The ocean emits a significant amount of CO₂ back into the atmosphere through the process of gas exchange

Land use changes(1.1)
deforestation, agriculture, and urbanization, result in the release of carbon stored in vegetation and soi

fossil fuels(7.8)
The combustion of fossil fuels (coal, oil, and natural gas) for energy and industrial processes releases carbon that has been stored underground for millions of years

Question 6

net change

Answer 6

net carbon assimilation on land (+2.6pg/yr)
net carbon assimilation ocean (+2.3pg/yr)
net carbon released in atmosphere
(landuse change and fossil fuel)
(-8.9pg/yr)

net flux= -4pg/yr (released into atmosphere)

Question 7

in ocean system

Answer 7

assimilation - phtosynthesis,calcite precipitation

decomposition
respiration
decalcification

Question 8

Inorganic carbon in the ocean is about x times larger than the amount held in organic
carbon.

Answer 8

40 times

Question 9

90%solubility 10% is due to the biological pump.

Question 10

Solubility Pump

Answer 10

The solubility of CO₂ in seawater is influenced by factors like temperature, salinity, and pressure. Cooler waters generally absorb more CO₂.

CO₂ reacts with seawater to form carbonic acid (H₂CO₃), which dissociates into bicarbonate (HCO₃⁻) and carbonate ions (CO₃²⁻).

Question 11

biological pumps

Answer 11

Phytoplankton in the ocean’s euphotic zone (sunlit surface waters) use CO₂ during photosynthesis to produce organic matter

then phytoplankton die or are consumed by zooplankton, the organic matter they contain is either consumed by other marine organisms or sinks to deeper waters

As organic matter sinks and reaches deeper waters, it is decomposed by microbes, releasing CO₂ back into the water column, which can then be transported to the deep ocean or returned to the atmosphere

Question 12

The surface DIC concentration

Answer 12

2000
μmol/kg.

Question 13

The deeper layers

Answer 13

2300 μmol/kg

Question 14

The equilibrium pump and biological pump regulates the DIC in the ocean?

Answer 14

increases the DIC concentration in the deep ocean, which can influence the solubility pump by affecting the CO₂ partial pressure in these deeper regions.

Question 15

What could be the reason for high DIC concentration in the deeper waters?

Answer 15

The biological pump significantly alters the natural distribution of DIC.
In the surface ocean, biological activity (photosynthesis) decreases DIC levels because carbon is taken up by organisms.
In the deep ocean, DIC concentrations are higher due to the remineralization of organic carbon by bacteria, and the lack of photosynthetic activity (due to absence of light

Question 16

ocean acidification

Answer 16

Ocean acidification refers to a reduction in the pH of the ocean over an extended period
of time, caused primarily by diffusion of excess carbon dioxide (CO2) from the atmosphere.

Question 17

how much reduction in pH

Answer 17

Today’s, average ocean pH = 8.1
The predicted pH in 2100 = 7.8

Question 18

Is it that significant?

Answer 18

Yes, because each decrease of one pH unit is a ten-fold increase in acidity.
pH is the logarithmic value of inverse of acidity

Question 19

Revelle factor

Answer 19

The higher the Revelle factor, the lower the ocean’s buffer capacity, and the faster the change of pCO2 in the ocean at a given DIC change.

A higher Revelle factor means that a small increase in DIC causes a larger increase in pCO₂, which indicates a lower buffer capacity. In contrast, a lower Revelle factor means the ocean can absorb more CO₂ without a significant increase in pCO₂, indicating a higher buffer capacity.

the ratio between the fractional change in (partial pressure of CO2 in the water) pCO2 to the fractional change in dissolved inorganic carbon (DIC) at constant temperature, salinity, and total alkalinity.

Revelle factor =
(ΔpCO2/pCO2 )/(ΔDIC/DIC)

Question 20

keeling curve fluctuations

Answer 20

but the otherwise increase trend is
due to anthropogenic activity
The increase in CO2 in fall and is due to deciduous trees over there shed leaves and release CO2 and stops photosynthesis.

The decrease in CO2 during spring
and summer is due to rejunuated trees and restarting photosynthesis.

Question 21

First CO2 measurement by Dr. Charles David Keeling

Answer 21

The very first report on increase in CO2 concentration after the industrial revolution.

• On May 9, 2013, the daily mean concentration of CO2 in the atmosphere measured
  at Mauna Loa surpassed 400 ppm.

Question 22

temp vs O 18

Answer 22

18
O18 is heavier than
16O , so it tends to condense and precipitate at a lower rate than
16O when temperatures are cooler.

There is a linear relationship between the
𝛿18/Oδ18 O of water and temperature. As temperature decreases, the ratio of
18O/16O in precipitated water (e.g., ice or snow) increases. Conversely, warmer temperatures result in a lower 18O/16O value because
18Ois less preferentially incorporated into the ice.

Question 23

Greenland Ice core, the layers are white and dark why?

Answer 23

The structure and size of ice crystals can vary with the season. Summer snow tends to have larger, more rounded crystals due to partial melting and refreezing, which reflects more light and makes the layer appear

the snow that does fall tends to be finer-grained. Moreover, the cold, dry conditions of winter favor the deposition of more dust and other particulates that get trapped in the snow.

Summer snow tends to be coarser, creating layers that are less tightly packed and more transmissive to light (brighter). Winter snow tends to be more fine-grained, and so it is more easily compacted by overlying snow or wind. Because of the compaction, winter snow layers tend to be darker than summer layers

Question 24

The CO2 increase after the industrial revolution is recorded by

Answer 24

Dr. David Keeling

Question 25

discovery of nitrogen

Answer 25

daniel rutherford

Question 26

inorganic

Question 27

strong component in destroying ozone layer.

Answer 27

Nitrous oxide

Question 28

reason for increase in N2O

Answer 28

due to increases in agriculture and to an small extent
certain chemical industries.

Question 29

acid rain contains

Answer 29

Nitric oxide

Question 30

nitogen fixation

Answer 30

N2 + 8H+ + 8e- + 16ATP = 2NH3+ +H2 + 16ADP +16Pi

Question 31

N2 fixers do their job at ambient temperature while Haber-Bosch process can do the same
at 300-500 0C and pressure 15-16 Mpa

Question 33

Nitrogenase

Answer 33

It is a complex of two proteins;
dinitrogenase and dinitrogenase reductase

Dinitrogenase contains both iron and either molybdenum (Mo)
or Vanadium.

Dinitrogenase contains only Iron protein codes with nifH gene. It has two identical
subunits with 4 Fe atoms.
two Mo atoms encoded with nifH and nifK

Nitrogenase is highly sensitive to oxygen, which can inactivate the enzyme. Marine N₂ fixers have developed strategies to protect nitrogenase from oxygen. For example, Trichodesmium creates specialized cells called heterocysts or fixes nitrogen during periods of low photosynthetic activity

Question 34

marine n2 fixers

Answer 34

cyanobacteria trichodesmium, richelia , calothrix

Question 35

DDAs

Answer 35

DDAs refer to diatom-diazotroph associations—a type of symbiotic relationship found in marine environments where nitrogen-fixing bacteria (diazotrophs) live in association with diatoms (a major group of microalgae). This symbiosis is particularly important in oligotrophic (nutrient-poor) regions of the ocean,

The diazotrophs in DDAs are usually cyanobacteria, with Richelia intracellularis and Calothrix rhizosoleniae being the most common partners. These bacteria fix atmospheric nitrogen (N₂) into ammonia (NH₃), making nitrogen available to both themselves and their diatom hosts.
The diazotrophs live within the diatom’s frustules (silica shells) or are closely associated with the diatom cells

Question 36

nitrification

Answer 36

2NH4+ + 3O2 → 2NO2– + 4H+ + 2H2O
2NO2– + O2 → 2NO3–

Question 37

Liebig Mineral theorem

Question 38

Dissimilatory Nitrate Reduction to Ammonia (DNRA)

Answer 38

NO3
− + 8e− + 10H+ → NH4

+ + 3H2O

Question 39

Anaerobic Ammonium Oxidation (ANAMMOX)

Question 40

(ANRA)Assimilatory nitrate reduction to ammonium

Answer 40

NO3
- → NO2

• → NH4

+ → is incorporated or converted into an amino acid

Azotobacter, Anabaena, Acinetobacter, Yeasts, Chlorella and all plants are able to
assimilate and convert the nitrate that is present in the environment into an amino group in
their own body or cell.

Question 41

ANNAMOX

Question 42

6CO2 +6H2O +48 photons of light 6O2 + C6H12O6

Question 43

Tropical region has high primary production
and hence, the nutrients are consumed fast.
* High nutrient low chlorophyll (HNLC) waters:

Question 43

Regenerated production:

Answer 43

The primary production that is
supported by regenerated nitrogen which are reduced forms
of N. NH4
+
, Urea etc.

Question 44

As temperature decreases
below 0°C, from left to right in
the figure, snow crystal
formation

Answer 44

2.From flat plates, to long
columns or needles, back to
plates again, and then to
columns and plates.

As humidity increases, the
snow crystals tend to get
bigger. Also, they tend to get
more branches or dendrites on
them.

Question 45

When these molecules solidify or freeze, they form a
hexagonal lattice due to electrostatic repulsion and
hydrogen bonding.
* The hydrogen “arms” of each molecule carry positive
electrical charges. Since like charges repel, the arms
maximize the distance between them.