CAS ES 107 Chapter Notes - Chapter 8: Silicate Minerals, Calcite, Primary Production
7 Jun 2018
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Chapter 8: Part 3
The Inorganic Carbon Cycle
-carbon dioxide readily dissolves in rainwater and seawater and then undergoes rapid chemical
reactions to other ionic forms of inorganic carbon
-the oxidized (inorganic) carbon in these waters is chemically reactive and becomes involved in a
number of chemical reactions
-they do not involve organic carbon directly
-the important reservoirs of inorganic carbon are the atmosphere, ocean, sediments, and
sedimentary rocks
-the sediment and sedimentary rock reservoirs consists primarily of limestone→ a rock
composed of calcium carbonate (CaCO3), in the form of the mineral calcite
Carbon exchange between the ocean and atmosphere
-in regions where high rates of primary productivity have created surface waters depleted of
CO2, Co2 diffuses from the atmosphere to the ocean
-so there’s a concentration gradient of carbon that goes from areas of high to low concentration
-upwelling regions have high CO2 concentrations because deep waters rich in CO2 have risen to
the surface
-in such regions, CO2 flows from the ocean to the atmosphere
-when CO2 dissolves in water, carbonic acid is generated, and these molecules break apart or
dissaociate into ions
-the relative abundance of carbon-bearing anions (neagative) is linked to the pH of seawater
-the disassociation of carbonic acid involes the release of one or both of its hydrogen atoms
-when the 1st hydrogen is lost, bicarbonate forms
-the H+ concentration were to decrease, then the pH increases
Chemical Weathering
Atmospheric CO2 dissolves in raindrops, making them naturally acidic
-crustal rocks are compsoed of two types…
-carbonate minerals (calcite) contain carbon in combo with oxygen and other elements
-silicate minerals contain compounds of silicon and oxygen
-they are most abundant in igneous rocks but are also found in sedimentary and metamorphic
rocks
-we are more interested in the weathering of calcium-bearing minerals because calcium ions
released by weathering are used by organisms in the construction of calcium carbonate shells and
skeletons
-when exposed to rain, carbonates and silicates weather chemically, but carbonates much faster
-chemical weathering neutralizes the acidity of carbonic acid
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Document Summary
Carbon dioxide readily dissolves in rainwater and seawater and then undergoes rapid chemical reactions to other ionic forms of inorganic carbon. The oxidized (inorganic) carbon in these waters is chemically reactive and becomes involved in a number of chemical reactions. The important reservoirs of inorganic carbon are the atmosphere, ocean, sediments, and sedimentary rocks. The sediment and sedimentary rock reservoirs consists primarily of limestone a rock composed of calcium carbonate (caco3), in the form of the mineral calcite. In regions where high rates of primary productivity have created surface waters depleted of. Co2, co2 diffuses from the atmosphere to the ocean. So there"s a concentration gradient of carbon that goes from areas of high to low concentration. Upwelling regions have high co2 concentrations because deep waters rich in co2 have risen to the surface. In such regions, co2 flows from the ocean to the atmosphere.
