Chapter 2.1 The Carbon Cycle

Abstract

This chapter discusses carbon cycle. Within its global biogeochemical cycle, the element carbon occurs in the form of various chemical compounds that are continuously being transformed and moved within two major, mutually interconnected cycles: (1) the inorganic carbon, or carbonate cycle in which carbon passes through a series of chemical equilibria; and (2) the organic carbon cycle in which carbon passes through the processes of biosynthesis and mineralization of organic matter. The cycling of the element carbon depends primarily on its chemical properties. Like nitrogen and sulfur, but unlike phosphorus, silica, and iron, carbon forms volatile, soluble, and insoluble compounds and can thus circulate through the atmosphere, hydrosphere, and lithosphere. Because carbon is the basic element of life, its circulation through the biosphere is of particular importance. From the global viewpoint, two interlocking carbon cycles have been recognized: the exogenic cycle (including the carbonate and the organic carbon cycles) with carbon cycled by the atmosphere, hydrosphere and biosphere, and the endogenic cycle, with carbon cycled by the crust of the earth, the lithosphere and, in part, by the external mantle.