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Diagram depicting the sources and cycles of acid rain precipitation. Freshwater acidification occurs when acidic inputs enter a body of fresh water through the weathering of rocks, invasion of acidifying gas (e.g. carbon dioxide), or by the reduction of acid anions, like sulfate and nitrate within a lake, pond, or reservoir. [1]
Ammonium and carbonic acid form bicarbonate and 2 moles of ammonium and hydroxide ions in water (3 &4). 2NH 3 + 2H 2 O ↔ 2NH + 4 +2OH − (3) H 2 CO 3 ↔ HCO − 3 + H + (4) The production of hydroxide ions results in the increase of pH, [35] which in turn can shift the bicarbonate equilibrium, resulting in the formation of carbonate ions (5)
Bedrock is dissolved by carbonic acid in rainwater, groundwater, or humic acids from decaying vegetation, that seeps through bedding planes, faults, joints, and the like.. Over time, the surface terrain breaks up into clints separated by grikes and punctuated by sinkholes into which streams may disappear, crevices expand as the walls are dissolved to become caves or cave sy
Speleogenesis is the origin and development of caves, the primary process that determines essential features of the hydrogeology of karst and guides its evolution. It often deals with the development of caves through limestone, caused by the presence of water with carbon dioxide dissolved within it, producing carbonic acid which permits the dissociation of the calcium carbonate in the limestone.
The holes may be caused by air bubbles or other foreign matter on the water surface. [3] Micrographs of calcite rafts show lace-like structure. The surface tension of the water keeps the interconnected calcite crystals, which individually have a specific gravity of 2.7, floating on the water surface.
Limestone forms when calcite or aragonite precipitate out of water containing dissolved calcium, which can take place through both biological and nonbiological processes. [41] The solubility of calcium carbonate (CaCO 3) is controlled largely by the amount of dissolved carbon dioxide (CO 2) in the water. This is summarized in the reaction:
Rain water contains dissolved carbon dioxide taken from the atmosphere. Some of the dissolved carbon dioxide reacts with the water to form carbonic acid, which remains in solution. Minerals containing calcium and magnesium form soluble bicarbonates when exposed to carbonic acid. Water containing these minerals is known as "hard water".
Calcite can be formed naturally or synthesized. However, artificial calcite is the preferred material to be used as a scaffold in bone tissue engineering due to its controllable and repeatable properties. [39] Calcite can be used to alleviate water pollution caused by the excessive growth of cyanobacteria.