carbon cycle Flashcards
Residence time
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
Flux in carbon
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
).
carbon flux
Flux is represented here as Peta
grams per year (Pg/year)
processes that assimilate carbon in environment
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.
processes that release the stored carbon
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
net change
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)
in ocean system
assimilation - phtosynthesis,calcite precipitation
decomposition
respiration
decalcification
Inorganic carbon in the ocean is about x times larger than the amount held in organic
carbon.
40 times
90%solubility 10% is due to the biological pump.
Solubility Pump
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⁻).
biological pumps
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
The surface DIC concentration
2000
μmol/kg.
The deeper layers
2300 μmol/kg
The equilibrium pump and biological pump regulates the DIC in the ocean?
increases the DIC concentration in the deep ocean, which can influence the solubility pump by affecting the CO₂ partial pressure in these deeper regions.
What could be the reason for high DIC concentration in the deeper waters?
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
ocean acidification
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.
how much reduction in pH
Today’s, average ocean pH = 8.1
The predicted pH in 2100 = 7.8
Is it that significant?
Yes, because each decrease of one pH unit is a ten-fold increase in acidity.
pH is the logarithmic value of inverse of acidity
Revelle factor
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)
keeling curve fluctuations
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.
First CO2 measurement by Dr. Charles David Keeling
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.
temp vs O 18
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.
Greenland Ice core, the layers are white and dark why?
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
The CO2 increase after the industrial revolution is recorded by
Dr. David Keeling
discovery of nitrogen
daniel rutherford
inorganic
strong component in destroying ozone layer.
Nitrous oxide
reason for increase in N2O
due to increases in agriculture and to an small extent
certain chemical industries.
acid rain contains
Nitric oxide
nitogen fixation
N2 + 8H+ + 8e- + 16ATP = 2NH3+ +H2 + 16ADP +16Pi
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
Nitrogenase
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
marine n2 fixers
cyanobacteria trichodesmium, richelia , calothrix
DDAs
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
nitrification
2NH4+ + 3O2 → 2NO2– + 4H+ + 2H2O
2NO2– + O2 → 2NO3–
Liebig Mineral theorem
Dissimilatory Nitrate Reduction to Ammonia (DNRA)
NO3
− + 8e− + 10H+ → NH4
+ + 3H2O
Anaerobic Ammonium Oxidation (ANAMMOX)
(ANRA)Assimilatory nitrate reduction to ammonium
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.
ANNAMOX
6CO2 +6H2O +48 photons of light 6O2 + C6H12O6
Tropical region has high primary production
and hence, the nutrients are consumed fast.
* High nutrient low chlorophyll (HNLC) waters:
Regenerated production:
The primary production that is
supported by regenerated nitrogen which are reduced forms
of N. NH4
+
, Urea etc.
As temperature decreases
below 0°C, from left to right in
the figure, snow crystal
formation
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.
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.
