Carbon dioxide cycle sinks

Carbon dioxide is likewise an inert material. As a result, its only known sinks are photosynthesis and solubility in seawater. The cycle of carbon dioxide through the atmosphere will be a major focal point in Chapter 11. 

Randerson, J. T., Thompson, M. V., Conway, T. J., Fung, I. Y. and Field, C. B. (1997). The contribution of terrestrial sources and sinks to trends in the seasonal cycle of atmospheric carbon dioxide. Global Biogeochem. Cycles 11,535-560. 

Resources such as biomass could provide a clean and sustainable resource for hydrogen production. As with fossil fuels, the processes that produce hydrogen gas from biomass all create carbon dioxide, but because the biomass acts as a carbon sink during the growing phase, the net carbon emission of the whole cycle is neutral. 

The citric acid cycle is at the heart of aerobic cellular metabolism, or respiration. This is true of both prokaryotic and eukaryotic organisms, of plants and animals, of organisms large and small. Here is the main point. On the one hand, the small molecule products of catabolism of carbohydrates, lipids, and amino acids feed into the citric acid cycle. There they are converted to the ultimate end products of catabolism, carbon dioxide and water. On the other hand, the molecules of the citric acid cycle are intermediates for carbohydrate, lipid, and amino acid synthesis. Thus, the citric acid cycle is said to be amphibolic, involved in both catabolism and anabolism. It is a sink for the products of degradation of carbohydrates, lipids, and proteins and a source of building blocks for them as well. 

Carbon dioxide mainly exits the oceans at the interface with the atmosphere. Warm surface waters easily release carbon dioxide into the atmosphere. When warm waters rise to the surface, mainly near the equator, carbon dioxide is transferred from the water to the air. Because of this, the sea is a source of carbon for the carbon cycle as well as a carbon sink. 

Moore, J. K., Abbott, M. R., Richman, J. G., Nelson, D. M. (2000). The Southern Ocean at the last glacial maximum A strong sink for atmospheric carbon dioxide. Global Biogeochem. Cycles 14, 455-475. 

Buitenhuis E. T., van der Wal P., and de Baar H. J. W. (2001) Blooms of Emiliania huxleyi are sinks of atmospheric carbon dioxide a field and mesocosm study derived simulation. Global Biogeochem. Cycles 15, 511-5%1. 

One of the most important components of the chemical perspective of oceanography is the carbonate system, primarily because it controls the acidity of seawater and acts as a governor for the carbon cycle. Within the mix of adds and bases in the Earth-surface environment, the carbonate system is the primary buffer for the aridity of water, which determines the reactivity of most chemical compoimds and solids. The carbonate system of the ocean plays a key role in controlling the pressure of carbon dioxide in the atmosphere, which helps to regulate the temperature of the planet. The formation rate of the most prevalent authigenic mineral in the environment, CaCOs, is also the major sink for dissolved carbon in the long-term global carbon balance. 

It can be seen that the great majority of carbon is cycled in the atmosphere as carbon dioxide. Thus, although the oxidation of CO provides an important sink, the process does not supply an important C02 source. It follows from the data given that the residence times of methane, carbon monoxide and carbon dioxide are 5.0 0.25 and 5.2 years, respectively. 

In the atmosphere, CO2 is affected by processes that operate on different time scales, including interaction with the silicate cycle (for more details, see Bashkin and Howarth, 2002), dissolution in the oceans, and annual cycles of photosynthesis and respiration (see also Section 4). The relative effect of these processes is described below taking into account the interrelationship between sources and sinks of carbon dioxide in the Asian region. Here, it is important to note that carbon dioxide is not reactive with other atmospheric species its MRT is three years (Figure 5). This value is largely determined by exchange with seawater (see below). 

Future changes in methane are difficult to estimate because we do not yet have complete knowledge of the sources and sinks of methane. The recent slowing down in the increase of methane is not well understood. Another problem concerns possible changes in the future carbon cycle. Will the future uptake of carbon in the terrestrial biosphere increase faster or slower than the emission of carbon dioxide or not To better understand the carbon cycle in a changing climate is one of the big challenges of the future. 

Inspection of the global carbon cycle provides a useful backdrop for considering the natural fate of wood. Terrestrial ecosystems accumulate an extremely small fraction of the organic matter photosynthesized within them. Almost all (>99%) of the organic material produced on land is remineralized back to carbon dioxide and water within an average half-life of 10-100 years 11). The small fraction that escapes is exported by rivers to lakes and coastal marine zones, where a portion of the plant debris becomes waterlogged, sinks, and is incorporated in bottom deposits (12). 

The ocean is evidently a major sink of carbon dioxide and plays an important role in the global carbon cycle. However, the carbon flux between seawater and sediment in the coastal seas is still poorly imderstood (Song, 2003 Li... 

The missing carbon concept arose because radiocarbon-calibrated carbon cycle models predict that the quantity of carbon remaining in the atmosphere after fossU fuel release should exceed that suggested by the direct observation of rising concentrations of carbon dioxide. Three solutions have been proposed. One is that current ocean models cannot be adequately calibrated using radiocarbon. A second is that the biosphere currently acts as a sink for carbon. The third is that the biosphere has been a net source of carbon in the past. 

Iron Fertilization of the Oceans. The intentional introduction of iron into the upper layers of certain areas of the ocean to encourage phytoplankton blooms is a form of CDR. The concept rehes on the fact that increasing certain nutrients—such as iron— in nutrient-poor areas stimulates phytoplankton growth. Carbon dioxide is absorbed from the surface of the ocean during the processes of photosynthesis when the phytoplankton, marine animals, and plankton die and sink in the natural cycle, that carbon is removed from the atmosphere and sequestered in the ocean s depths. 

Life cycle assessment reveals that no petroleum-derived polymer can rival the greenhouse gas sink effect of the improved PLA process. Although disposal of PLA products - whether by combustion, composting or other conventional means - results in a return of carbon dioxide to the atmosphere, this advantage survives. 

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