Carbon cycle weathering

The efficiency of the weathering of rocks in using carbonic acid produced in the carbon cycle is affected by various hydrologic, environmental, and cultural controls. The fact that the principal anion in fresh surface water worldwide almost always is bicarbonate attests to the overriding importance of this process. Exceptions are systems in which evaporite minerals are available for dissolution by groundwater or where human activities are major sources of sulfate or chloride inflow. 

Land/atmospheric interfacial processes which impact climate and biological activity on earth are illustrated in Figure 3. Emissions of carbon dioxide, methane, nitrogen dioxide, and chlorofluorocarbons (CFCs) have been linked to the transmission of solar radiation to the surface of the earth as well as to the transmission of terrestrial radiation to space. Should solar radiation be an internal process or an external driver of the hydrologic cycle, weather, and air surface temperatures Compounds of sulfur and nitrogen are associated with acidic precipitation and damage to vegetation, aquatic life, and physical structures. 

Stallard, R. F. (1998). Terrestrial sedimentation and the carbon cycle Coupling weathering and erosion to carbon burial. Glob. Biogeochem. Cycles 12, 231-252. 

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... 

To begin the discussion, we will present briefly a view of the modern carbon cycle, with emphasis on processes, fluxes, reservoirs, and the "CO2 problem". In Chapter 4 we introduced this "problem" here it is developed further. We will then investigate the rock cycle and the sedimentary cycles of those elements most intimately involved with carbon. Weathering processes and source minerals, basalt-seawater reactions, and present-day sinks and oceanic balances of Ca, Mg, and C will be emphasized. The modern cycles of organic carbon, phosphorus, nitrogen, sulfur, and strontium are presented, and in Chapter 10 linked to those of Ca, Mg, and inorganic C. In conclusion in Chapter 10, aspects of the historical geochemistry of the carbon cycle are discussed, and tied to the evolution of Earth s surface environment. 

Field studies have shown that the rate of silicate weathering can be increased by plants by a factor —(2-10). Use of these values in modeling of the long-term geological carbon cycle shows that the... 

Sharp M., Parkes J., Cragg B., Fairchild I. J., Lamb H., and Tranter M. (1999) Bacterial populations at glacier beds and their relationship to rock weathering and carbon cycling. Geology 27, 107-110. 

The carbon cycle and its long-term influence on climate through the weathering of fresh silicate rocks (Berner et al., 1983) has created a new interest in the river transfer of carbon. Bicarbonate (HCOj") is the dominant form of Die in the pH range of most world rivers... 

Fine clastic sediments, mostly mudrocks, in contrast to their coarser counterparts, are either derived by first cycle weathering of silicate minerals or glass, or from recycling of older mudrocks. Physical comminution plays only a secondary role. The average shale is composed of 40-60% clay minerals, 20-30% quartz, 5-10% feldspar and minor iron oxide, carbonate, organic matter, and other components (Yaalon, 1962 Shaw and Weaver, 1965). Granitic source rocks produce shales richer in kaolinite and illite, the... 

There are two major carbon cycles on Earth. The two cycles operate in parallel. One cycle is slow and abiotic. Its effects are observed on multimillion-year timescales and are dictated by tectonics and weathering (Berner, 1990). In this cycle, CO2 is released from the mantle to the atmosphere and oceans via vulcanism and seafloor spreading, and removed from the atmosphere and ocean primarily by reaction with silicates to form carbonates in the latter reservoir. Most of the carbonates are subsequently subducted into the mantle, where they are heated, and their carbon is released as CO2 to the atmosphere and ocean, to carry out the cycle again. The chemistry of this cycle is dependent on acid-base reactions, and would operate whether or not there was life on the planet (Kasting et al., 1988). This slow carbon cycle is a critical determinate of the concentration of CO2 in Earth s atmosphere and oceans on timescales of tens and hundreds of milhons of years (Kasting, 1993). 

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