Dissolved inorganic carbon

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Annual DOC and DIC fluxes in the Tanguro Ranch watershed Average annual flux of DOC and DIC in rainfall, throughfall, stemflow, overland flow, and stream flow. Annual DOC and DIC fluxes in the Tanguro Ranch watershed.jpg
Annual DOC and DIC fluxes in the Tanguro Ranch watershed
Average annual flux of DOC and DIC in rainfall, throughfall, stemflow, overland flow, and stream flow.

Dissolved inorganic carbon (DIC) is the sum of the aqueous species of inorganic carbon in a solution. Carbon compounds can be distinguished as either organic or inorganic, and as dissolved or particulate, depending on their composition. Organic carbon forms the backbone of key component of organic compounds such as – proteins, lipids, carbohydrates, and nucleic acids.

Contents

Inorganic carbon is found primarily in simple compounds such as carbon dioxide, carbonic acid, bicarbonate, and carbonate (CO2, H2CO3, HCO−
3, CO2−
3 respectively). Dissolved inorganic carbon (DIC) includes three major aqueous species, CO2, HCO−
3 ,CO2−
3, and to a lesser extent their complexes in solution with metal ions. [3]

Marine ecosystems

Solubility pump

Aqueous carbon dioxide reacts with water to form carbonic acid which is very unstable and will dissociate rapidly into hydronium and bicarbonate. Therefore, in seawater, dissolved inorganic carbon is commonly referred to as the collection of bicarbonate, carbonate ions, and dissolved carbon dioxide (CO2, H2CO3, HCO−
3, CO2−
3).

CO2(aq) + H2O ⇌ H2CO3⇌HCO−
3 + H+⇌CO2−
3 + 2 H+

More than 99% of dissolved inorganic carbon is in the form of bicarbonate and carbonate ions meaning that most of the ocean’s carbon storing ability is due to this chemical reactivity. [4] Sea-air flux of CO2 and the resulting dissolved inorganic carbon is affected by physical processes such as strong winds and vertical mixing, and the biological processes of photosynthesis, respiration, and decomposition. [5]

Biological pump

Dissolved inorganic carbon is a key component of the biological pump, which is defined as the amount of biologically produced organic carbon flux from the upper ocean to the deep ocean. [6] Dissolved inorganic carbon in the form of carbon dioxide is fixed into organic carbon through photosynthesis. Respiration is the reverse process and consumes organic carbon to produce inorganic carbon. Photosynthesis, and the biological pump, is dependent on the availability of inorganic nutrients and carbon dioxide. [7]

Photosynthesis: 6 CO2 + 6 H2O + light → C6H12O6 + 6 O2
Respiration: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy

Oceanographers seek to understand the metabolic state of the ocean, or the efficiency of the biological pump, by estimating the net community production (NCP) which is the gross primary productivity (GPP) minus the community respiration (sum of the respiration of the local autotrophs and heterotrophs). [8] An efficient biological pump increases biological export to the deeper ocean which has been hypothesized to suppress CO2 outgassing in the upper ocean. [9] [10]

Annual mean sea surface dissolved inorganic carbon for the 1990s (GLODAP).png
"Present day" (1990s)
Estimated annual mean sea surface dissolved inorganic carbon for the 1700s (GLODAP).png
Pre-Industrial Revolution (1700s)
           Sea surface DIC concentration (from GLODAP climatology)
Spatial distribution of ocean surface DIC Spatial distributions of DIC and nDIC. (a) DIC (normalized to year 2005); (b) salinity-normalized DIC (nDIC, DIC normalized to reference year of 2005 and salinity of 35) in the surface global ocean. The latitudinal trends are clear, particularly for nDIC. Spatial distribution of ocean surface dissolved inorganic carbon.png
Spatial distribution of ocean surface DIC
Spatial distributions of DIC and nDIC. (a) DIC (normalized to year 2005); (b) salinity-normalized DIC (nDIC, DIC normalized to reference year of 2005 and salinity of 35) in the surface global ocean. The latitudinal trends are clear, particularly for nDIC.

Carbonate pump

The carbonate pump is sometimes referred to as the “hard tissue” component of the biological pump. [12] Some surface marine organisms, like Coccolithophores, produce hard structures out of calcium carbonate, a form of particulate inorganic carbon, by fixing bicarbonate. [13] This fixation of DIC is an important part of the oceanic carbon cycle.

Ca2+ + 2 HCO−
3 → CaCO3 + CO2 + H2O

While the biological carbon pump fixes inorganic carbon (CO2) into particulate organic carbon in the form of sugar (C6H12O6), the carbonate pump fixes inorganic bicarbonate and causes a net release of CO2. [14] In this way, the carbonate pump could be termed the carbonate counter pump. It works counter to the biological pump by counteracting the CO2 flux from the biological pump.

Measurement

Oceanographers and engineers continue to find novel and more accurate methods of measuring carbon content in seawater. One method is to collect water samples and directly measure the DIC by using a TOC analyzer. [15] Samples can be combined with stable isotope ratios 13C/12C, alkalinity measurements, and estimation of physical processes, to create diagnostic techniques. [16] Researchers at Scripps Institution of Oceanography developed a tool that uses flow injection analysis to measures microfluidic samples of seawater and continuously monitor dissolved inorganic carbon content. [17]

See also

Related Research Articles

<span class="mw-page-title-main">Bicarbonate</span> Polyatomic anion

In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula HCO−
3.

<span class="mw-page-title-main">Carbon dioxide</span> Chemical compound with formula CO₂

Carbon dioxide is a chemical compound with the chemical formula CO2. It is made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature and at normally-encountered concentrations it is odorless. As the source of carbon in the carbon cycle, atmospheric CO2 is the primary carbon source for life on Earth. In the air, carbon dioxide is transparent to visible light but absorbs infrared radiation, acting as a greenhouse gas. Carbon dioxide is soluble in water and is found in groundwater, lakes, ice caps, and seawater.

<span class="mw-page-title-main">Carbonate</span> Salt or ester of carbonic acid

A carbonate is a salt of carbonic acid,, characterized by the presence of the carbonate ion, a polyatomic ion with the formula CO2−3. The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate groupO=C(−O−)2.

<span class="mw-page-title-main">Carbon cycle</span> Natural processes of carbon exchange

The carbon cycle is that part of the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of Earth. Other major biogeochemical cycles include the nitrogen cycle and the water cycle. Carbon is the main component of biological compounds as well as a major component of many rocks such as limestone. The carbon cycle comprises a sequence of events that are key to making Earth capable of sustaining life. It describes the movement of carbon as it is recycled and reused throughout the biosphere, as well as long-term processes of carbon sequestration (storage) to and release from carbon sinks.

<span class="mw-page-title-main">Coccolithophore</span> Unicellular algae responsible for the formation of chalk

Coccolithophores, or coccolithophorids, are single-celled organisms which are part of the phytoplankton, the autotrophic (self-feeding) component of the plankton community. They form a group of about 200 species, and belong either to the kingdom Protista, according to Robert Whittaker's five-kingdom system, or clade Hacrobia, according to a newer biological classification system. Within the Hacrobia, the coccolithophores are in the phylum or division Haptophyta, class Prymnesiophyceae. Coccolithophores are almost exclusively marine, are photosynthetic and mixotrophic, and exist in large numbers throughout the sunlight zone of the ocean.

<span class="mw-page-title-main">Carbonic acid</span> Chemical compound

Carbonic acid is a chemical compound with the chemical formula H2CO3. The molecule rapidly converts to water and carbon dioxide in the presence of water. However, in the absence of water, it is quite stable at room temperature. The interconversion of carbon dioxide and carbonic acid is related to the breathing cycle of animals and the acidification of natural waters.

<span class="mw-page-title-main">Biological pump</span> Carbon capture process in oceans

The biological pump (or ocean carbon biological pump or marine biological carbon pump) is the ocean's biologically driven sequestration of carbon from the atmosphere and land runoff to the ocean interior and seafloor sediments. In other words, it is a biologically mediated process which results in the sequestering of carbon in the deep ocean away from the atmosphere and the land. The biological pump is the biological component of the "marine carbon pump" which contains both a physical and biological component. It is the part of the broader oceanic carbon cycle responsible for the cycling of organic matter formed mainly by phytoplankton during photosynthesis (soft-tissue pump), as well as the cycling of calcium carbonate (CaCO3) formed into shells by certain organisms such as plankton and mollusks (carbonate pump).

A hydrogen ion is created when a hydrogen atom loses an electron. A positively charged hydrogen ion (or proton) can readily combine with other particles and therefore is only seen isolated when it is in a gaseous state or a nearly particle-free space. Due to its extremely high charge density of approximately 2×1010 times that of a sodium ion, the bare hydrogen ion cannot exist freely in solution as it readily hydrates, i.e., bonds quickly. The hydrogen ion is recommended by IUPAC as a general term for all ions of hydrogen and its isotopes. Depending on the charge of the ion, two different classes can be distinguished: positively charged ions and negatively charged ions.

The pedosphere is the outermost layer of the Earth that is composed of soil and subject to soil formation processes. It exists at the interface of the lithosphere, atmosphere, hydrosphere and biosphere. The pedosphere is the skin of the Earth and only develops when there is a dynamic interaction between the atmosphere, biosphere, lithosphere and the hydrosphere. The pedosphere is the foundation of terrestrial life on Earth.

<span class="mw-page-title-main">Alkalinity</span> Capacity of water to resist changes in pH that would make the water more acidic

Alkalinity (from Arabic: القلوية, romanized: al-qaly, lit. 'ashes of the saltwort') is the capacity of water to resist acidification. It should not be confused with basicity, which is an absolute measurement on the pH scale. Alkalinity is the strength of a buffer solution composed of weak acids and their conjugate bases. It is measured by titrating the solution with an acid such as HCl until its pH changes abruptly, or it reaches a known endpoint where that happens. Alkalinity is expressed in units of concentration, such as meq/L (milliequivalents per liter), μeq/kg (microequivalents per kilogram), or mg/L CaCO3 (milligrams per liter of calcium carbonate). Each of these measurements corresponds to an amount of acid added as a titrant.

<span class="mw-page-title-main">Solubility pump</span> Physico-chemical process which transports carbon

In oceanic biogeochemistry, the solubility pump is a physico-chemical process that transports carbon as dissolved inorganic carbon (DIC) from the ocean's surface to its interior.

pCO<sub>2</sub> Partial pressure of carbon dioxide, often used in reference to blood

pCO2, pCO2, or is the partial pressure of carbon dioxide (CO2), often used in reference to blood but also used in meteorology, climate science, oceanography, and limnology to describe the fractional pressure of CO2 as a function of its concentration in gas or dissolved phases. The units of pCO2 are mmHg, atm, torr, Pa, or any other standard unit of atmospheric pressure. The pCO2 of Earth's atmosphere has risen from approximately 280 ppm (parts-per-million) to a mean 2019 value of 409.8 ppm as a result of anthropogenic release of carbon dioxide from fossil fuel burning. This is the highest atmospheric concentration to have existed on Earth for at least the last 800,000 years.

<span class="mw-page-title-main">Carbonate–silicate cycle</span> Geochemical transformation of silicate rocks

The carbonate–silicate geochemical cycle, also known as the inorganic carbon cycle, describes the long-term transformation of silicate rocks to carbonate rocks by weathering and sedimentation, and the transformation of carbonate rocks back into silicate rocks by metamorphism and volcanism. Carbon dioxide is removed from the atmosphere during burial of weathered minerals and returned to the atmosphere through volcanism. On million-year time scales, the carbonate-silicate cycle is a key factor in controlling Earth's climate because it regulates carbon dioxide levels and therefore global temperature.

<span class="mw-page-title-main">Marine snow</span> Shower of organic detritus in the ocean

In the deep ocean, marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the water column. It is a significant means of exporting energy from the light-rich photic zone to the aphotic zone below, which is referred to as the biological pump. Export production is the amount of organic matter produced in the ocean by primary production that is not recycled (remineralised) before it sinks into the aphotic zone. Because of the role of export production in the ocean's biological pump, it is typically measured in units of carbon. The term was coined by explorer William Beebe as observed from his bathysphere. As the origin of marine snow lies in activities within the productive photic zone, the prevalence of marine snow changes with seasonal fluctuations in photosynthetic activity and ocean currents. Marine snow can be an important food source for organisms living in the aphotic zone, particularly for organisms that live very deep in the water column.

<span class="mw-page-title-main">Oceanic carbon cycle</span> Ocean/atmosphere carbon exchange process

The oceanic carbon cycle is composed of processes that exchange carbon between various pools within the ocean as well as between the atmosphere, Earth interior, and the seafloor. The carbon cycle is a result of many interacting forces across multiple time and space scales that circulates carbon around the planet, ensuring that carbon is available globally. The Oceanic carbon cycle is a central process to the global carbon cycle and contains both inorganic carbon and organic carbon. Part of the marine carbon cycle transforms carbon between non-living and living matter.

Estuarine acidification happens when the pH balance of water in coastal marine ecosystems, specifically those of estuaries, decreases. Water, generally considered neutral on the pH scale, normally perfectly balanced between alkalinity and acidity. While ocean acidification occurs due to the ongoing decrease in the pH of the Earth's oceans, caused by the absorption of carbon dioxide (CO2) from the atmosphere, pH change in estuaries is more complicated than in the open ocean due to direct impacts from land run-off, human impact, and coastal current dynamics. In the ocean, wave and wind movement allows carbon dioxide (CO2) to mixes with water (H2O) forming carbonic acid (H2CO3). Through wave motion this chemical bond is mixed up, allowing for the further break of the bond, eventually becoming carbonate (CO3) which is basic and helps form shells for ocean creatures, and two hydron molecules. This creates the potential for acidic threat since hydron ions readily bond with any Lewis Structure to form an acidic bond. This is referred to as an oxidation-reduction reaction.

Community respiration (CR) refers to the total amount of carbon-dioxide that is produced by individuals organisms in a given community, originating from the cellular respiration of organic material. CR is an important ecological index as it dictates the amount of production for the higher trophic levels and influence biogeochemical cycles. CR is often used as a proxy for the biological activity of the microbial community.

<span class="mw-page-title-main">Marine biogenic calcification</span> Shell formation mechanism

Marine biogenic calcification is the production of calcium carbonate by organisms in the global ocean.

<span class="mw-page-title-main">Total inorganic carbon</span> Sum of the inorganic carbon species

Total inorganic carbon is the sum of the inorganic carbon species.

<span class="mw-page-title-main">Particulate inorganic carbon</span>

Particulate inorganic carbon (PIC) can be contrasted with dissolved inorganic carbon (DIC), the other form of inorganic carbon found in the ocean. These distinctions are important in chemical oceanography. Particulate inorganic carbon is sometimes called suspended inorganic carbon. In operational terms, it is defined as the inorganic carbon in particulate form that is too large to pass through the filter used to separate dissolved inorganic carbon.

References

  1. ↑ Environmental Research at Tanguro Ranch, Brazil Esri. Retrieved 26 July 2020.
  2. ↑ Neu, V., Ward, N.D., Krusche, A.V. and Nill, C. (2016) "Dissolved organic and inorganic carbon flow paths in an Amazonian transitional forest". Frontiers in Marine Science, 3: 114. doi : 10.3389/fmars.2016.00114. CC-BY icon.svg Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.
  3. ↑ Mackenzie FT and Lerman A (2006) Carbon in the Geobiosphere: Earth's Outer Shell, Springer Science & Business Media. ISBN   9781402042386.
  4. ↑ Williams, Richard G.; Follows, Michael J. (14 July 2011). Ocean Dynamics and the Carbon Cycle: Principles and Mechanisms. Cambridge, UK: Cambridge University Press. pp. 7–9. ISBN   978-0521843690.
  5. ↑ Ma, W; Chai, F; Xiu, P; Tian, J (2014). "Simulation of export production and biological pump structure in the South China Sea". Geo-Marine Letters. 34 (6): 541–554. Bibcode:2014GML....34..541M. doi:10.1007/s00367-014-0384-0. S2CID   129982048.
  6. ↑ Emerson, Steven (2014). "Annual net community production and the biological carbon flux in the ocean". Global Biogeochemical Cycles. 28 (1): 14–28. Bibcode:2014GBioC..28...14E. doi: 10.1002/2013GB004680 .
  7. ↑ Raymond, Peter A.; Bauer, James E. (2000). "Atmospheric CO2 evasion, dissolved inorganic carbon production, and net heterotrophy in the York River estuary". Limnol. Oceanogr. 45 (8): 1707–1717. Bibcode:2000LimOc..45.1707R. doi: 10.4319/lo.2000.45.8.1707 .
  8. ↑ Ducklow, H.W.; Doney, S.C. (2013). "What is the Metabolic State of the Oligotrophic Ocean? A Debate". Annual Review of Marine Science. 5: 525–33. doi:10.1146/annurev-marine-121211-172331. hdl: 1912/5282 . PMID   22809191.
  9. ↑ Ma, W; Chai, F; Xiu, P; Tian, J (2014). "Simulation of export production and biological pump structure in the South China Sea". Geo-Marine Letters. 34 (6): 541–554. Bibcode:2014GML....34..541M. doi:10.1007/s00367-014-0384-0. S2CID   129982048.
  10. ↑ Kim, H.J.; Kim, T.-W; Hyeong, K; Yeh, S.-W.; Park, J.-Y.; Yoo, C.M.; Hwang, J. (2019). "Suppressed CO2 Outgassing by an Enhanced Biological Pump in the Eastern Tropical Pacific". Journal of Geophysical Research: Oceans. 124 (11): 7962–7973. Bibcode:2019JGRC..124.7962K. doi:10.1029/2019JC015287. S2CID   210611691.
  11. ↑ Wu, Y., Hain, M.P., Humphreys, M.P., Hartman, S. and Tyrrell, T. (2019) "What drives the latitudinal gradient in open-ocean surface dissolved inorganic carbon concentration?" Biogeosciences, 16(13): 2661–2681. doi:10.5194/bg-16-2661-2019. CC-BY icon.svg Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.
  12. ↑ Hain, M.P.; Sigman, D.M.; Haug, G.H (2014). "The Biological Pump in the Past". Treatise on Geochemistry. 8: 485–517. doi:10.1016/B978-0-08-095975-7.00618-5. ISBN   9780080983004.
  13. ↑ Rost, Bjorn; Reibessel, Ulf (2004). Coccolithophores and the biological pump: responses to environmental changes. Berlin, Heidelberg: Springer. ISBN   978-3-642-06016-8.
  14. ↑ Rost, Bjorn; Reibessel, Ulf (2004). Coccolithophores and the biological pump: responses to environmental changes. Berlin, Heidelberg: Springer. ISBN   978-3-642-06016-8.
  15. ↑ Raymond, Peter A.; Bauer, James E. (2000). "Atmospheric CO2 evasion, dissolved inorganic carbon production, and net heterotrophy in the York River estuary". Limnol. Oceanogr. 45 (8): 1707–1717. Bibcode:2000LimOc..45.1707R. doi: 10.4319/lo.2000.45.8.1707 .
  16. ↑ Gruber, Nicolas; Kneeling, Charles D.; Stocker, Thomas F. (1998). "Carbon-13 constraints on the seasonal inorganics carbon budget at the BATS site in the northwestern Sargasso Sea". Deep-Sea Research Part I. 45 (4–5): 673–717. Bibcode:1998DSRI...45..673G. doi:10.1016/S0967-0637(97)00098-8.
  17. ↑ Bresnahan, Philip J.; Martz, Todd R. (2018). "Gas Diffusion Cell Geometry for a Microfluidic Dissolved Inorganic Carbon Analyzer". IEEE Sensors Journal. 8 (6): 2211–2217. Bibcode:2018ISenJ..18.2211B. doi: 10.1109/JSEN.2018.2794882 . S2CID   3475999.
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