Sulfur-carbon-oxygen cycle

Coupled Geochemical Cycle Sulfur-Carbon-Oxygen (S-C-O) Cycle... 

Here classical work of Garrels and Lerman (1984) which treated sulfur-carbon-oxygen (S-C-O) global cycle is briefly shown below. The relationships between S, C, and O cycles are derived from the following reactions. 

Van Cappellen, P. Wang Y. 1996. Cycling of iron and manganese in surface sediments a general theory for the coupled transport and reaction of carbon, oxygen, nitrogen, sulfur, iron and manganese. American Journal Sciences, 296, 197-243. 

Earth, with its four spheres, is a good approximation of a closed system. As you learned in Unit 4, a closed system is subject to the principles of equilibrium. Every change to the system affects the whole equilibrium. Elements such as carbon, nitrogen, sulfur, and oxygen regularly cycle through Earth s four spheres. Thus, Earth is in a constant dynamic equilibrium. 

Figure 10.35. Coupling between the carbon, oxygen, and sulfur cycles. A. CO2-O2 connection. B. CO2-O2-S connection. Fluxes are average Phanerozoic values in units of lQl2 moles y-1. See text for discussion.

Garrels R.M. and Perry E.A., Jr. (1974) Cycling of carbon, sulfur and oxygen through geologic time. In The Sea, Volume 5 (ed. E.D. Goldberg) pp. 303-336. Wiley-Interscience, New York. 

There are 5 major reservoirs in the Earth system atmosphere, biosphere (vegetation, animals), soils, hydrosphere (oceans, lakes, rivers, groundwater), and the lithosphere (Earth crust). Elemental cycles of carbon, oxygen, nitrogen, sulfur, phosphorus, and other elements interact with the different reservoirs of the Earth system. The carbon cycle has important aspects in tropical forests due to the large amount of carbon stored in the tropical forests and the high rate of tropical deforestation 0acob 1999)-... 

Figure 1 Conceptual model for the origin of mixed detrital-biogenic facies relating the three major inputs to the processes that control them. The major inputs are shown in boxes with bold-type labels. ControlUng factors are shown in italics. Large and medium scale arrows represent fluxes of key components involved in sedimentation and the biogeochemical cycles of carbon, sulfur, and oxygen. Thin arrows illustrate relationships between major controlling factors and depositional processes and/or feedback. Dashed thin arrows apply to major nutrient fluxes only. Dotted thin arrows apply to major authigenic fluxes only. See text for further explanation.

Schidlowski M. and Junge C. E. (1981) Coupling among the terrestrial sulfur, carbon and oxygen cycles numerical... 

Walker J. C. G. (1979) The early history of oxygen and ozone in the atmosphere. Pure Appl. Geophys. 117, 498-512. Walker J. C. G. (1986) Global geochemical cycles of carbon, sulfur, and oxygen. Mar. Geol. 70, 159-174. 

The formation of reduced carbon can account for the qualitative features of the oxygen cycle. The fate of the reduced carbon in sediments is, however, coupled with the sulfur cycle, as described by Berner (1984) and Garrels and Lerman (1981). Some of the reduced carbon may be oxidized by bacteria under anoxic conditions with sulfate acting as the oxidizing agent. The carbon is fully oxidized to carbonate and the sulfur is reduced in several stages to a sulfide or to iron pyrite. The "stripped-down", balanced, chemist s redox equation is ... 

The spontaneity of this reaction is reflected in the AG value of — 125kJ/mol(C). The result is that the total equivalents of reduced matter produced by carbon burial are redistributed and now include some pyrite. Sulfate is removed from the water permeating the sediments and magnesium and calcium carbonates are formed. Thus, the carbon, oxygen, and sulfur cycles are coupled by a redox reaction which also includes iron. The extent of the coupling depends on the supplies of reactive organic carbon, sulfate, and reactive iron. When the reduced material is returned to contact with the atmosphere, it is oxidized and an amount of oxygen equivalent to that formed when the carbon was first buried is removed. 

Van Cappellen, P. and Wang, Y., 1996. Cycling of Iron and Manganese in Surface Sediments A General Theory for the Coupled Transport and Reaction of Carbon, Oxygen, Nitrogen, Sulfur, Iron, and Manganese.-American Journal of Science, 296, 197-243. 

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