Carbon cycle, deep

Combining Eqs. 25.3 and 25.5 yields the net effect of the deep carbon cycle,... 

This is a very sketchy depiction of the deep carbon cycle because it illustrates only the behaviors of calcium and silica. In reality, a wide variety of other cations are present in the silicate minerals, such as in the plagioclase feldspars (Table 13.2). Furthermore, not all of the limestone is converted into siUcate minerals some remains as limestone. Uplift of the limestone onto land, followed by chemical and biological weathering, is another sink for atmospheric CO2, via... 

Alternatives to fossil fuels, such as hydrogen, are explored in Box 6.2 and Section 14.3. Coal, which is mostly carbon, can be converted into fuels with a lower proportion of carbon. Its conversion into methane, CH4, for instance, would reduce C02 emissions per unit of energy. We can also work with nature by accelerating the uptake of carbon by the natural processes of the carbon cycle. For example, one proposed solution is to pump C02 exhaust deep into the ocean, where it would dissolve to form carbonic acid and bicarbonate ions. Carbon dioxide can also be removed from power plant exhaust gases by passing the exhaust through an aqueous slurry of calcium silicate to produce harmless solid products ... 

The oceanic carbon inventory was presented in Table 15.3. Most of the carbon is inorganic (98%), predominantly in the form of bicarbonate (87%), and is located in the intermediate and deep waters. Of the 2% that is organic, the majority is DOC (see Table 23.2). At present, the ocean is acting as a net sink for atmospheric CO2. In the modern-day carbon cycle, the sole oceanic sink fitr carbon is burial in the sediments in the form of detrital biogenic PIC and POC. 

Climate changes from the time ofthe disappearance of dinosaurs to our days have also been based up on deep-sea stable isotope data oxygen isotope data provide an insight into the temperature variations, while carbon isotope data are informative on the kind of global carbon cycle perturbation (Zachos 2001). These data suggest that the present conditions of temperature are similar to the late Middle Age. However, the trend toward higher temperatures is now more difficult to contrast because of the drastic deforestation and emission of gases. 

The land, which includes the soils on the surface of Earth as well as the rocks and sediments deep in the ground and under the oceans, contains most of the carbon in the carbon cycle. The rocks under Earths surface hold about 65 million Gt of carbon the soils on the surface hold over 1,500 Gt of carbon. Underground, much of the carbon is in fossil fuels—coal, oil, and natural gas. 

There is also a great need to measure DON with accuracy. DON is the primary form of nitrogen in much of the surface ocean and may limit phytoplankton production in many areas. The difficulty in measuring DON is largely analytical, and accurate values for deep water will only be obtained after new direct DON methods are developed. Measurement of certain forms of DON is probably more important for understanding the global carbon cycle than is knowledge of concentrations for most trace metals. 

Deming, J. W., and P. L. Yager. 1992. Natural bacterial assemblages in deep-sea sediments Towards a global view. In Deep-Sea Food Chains and the Global Carbon Cycle. Kluwer, Dordrecht, the Netherlands. 

Curry W.B. and Lohmann G.P. (1985) Carbon deposition rates and deep water residence time in the equatorial Atlantic Ocean throughout the last 160,000 years. In The Carbon Cycle and Atmospheric CO2 Natural Variations Archean to Present (eds. E.T. Sundquist and W.S. Broecker), pp. 285-301. Amer. Geophys. Union, Washington, D.C. 

Smith DC, Steward GF, Long RA, Azam F (1995) Bacterial mediation of carbon fluxes during a diatom bloom in a mesocosm. Deep Sea Res II 42 75-97 Smith WO, Codispoti LA, Nelson DM, Manley T, Buskey EJ, Niebauer HJ, Cota GF (1991) Importance of Phaeocystis blooms in the high-latitude ocean carbon cycle. Nature 352 514—516... 

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