User:Edstr121/Aluminum cycle

Aluminum is the third most abundant element in the lithosphere at 82,000 ppm. It occurs in low levels, 0.9 ppm, in humans. Aluminum is known to be an ecotoxicant and expected to be a health risk to people. Global primary production (GPP) of aluminum was about 52 million tons in 2013 and remains one of the world's most important metals. It is used for infrastructure, vehicles, aviation, energy and more due to its lightweight, ductility, and cheap cost. Aluminum is harvested from gibbsite, boehmite, and diaspore which make up bauxite. PREVIOUS INFO The biogeochemical cycle of aluminum is integral with silicon and phosphorus. For example, phosphates store aluminum that has been sedimented and aluminum is found in diatoms (made of silica). Aluminum has been found to prevent growth in organisms by making phosphates less available. The humans/lithosphere ratio (B/L) is very low at 0.000011. This level shows that aluminum is more essential in the lithospheric cycle than biotic cycle.

Lithospheric Cycle

Aluminum makes up 8% of the Earth’s crust. (mobilization) The majority of aluminum cycling takes place in the lithosphere via sedimentary processes, with 99.999% of aluminum cycled within the lithosphere in the form of primary and secondary minerals as well as colloidal phases. Primary aluminum-rich minerals, such as feldspars, in the Earth's crust are weathered to clay-like materials such as kaolinite. Feldspars are formed when magma cools within Earth’s crust and are weathered away from the parent material. The secondary mineral, kaolinite, forms from carbonic acid weathering. Other secondary minerals include hydroxyaluminosilicates and aluminum hydroxide which are insoluble. They adsorb on mineral and organic surfaces. (1) Clays generally have low solubility and are eventually returned to crust through sedimentation and subduction. Aluminum is then found as an unstable primary mineral. Aluminum goes through several dissolution and precipitation processes when the element is in an aqueous phase, meaning it was dissolved. (1) With further weathering, aluminum is transported as particulates in rivers. Aluminum can also be carried through the atmosphere via dust. (mobilization)

Biotic cycle

Aluminum enters the biosphere through water and food as soluble aluminum, Al³⁺ or AlF²⁺. It is then cycled through the food chain. Aluminum has a low abundance in the biosphere but can be found in all organisms. (1) Humans, animals, and plants accumulate aluminum throughout their lives as it cycled throughout the food chain. There is no evidence to support aluminum being essential to humans or in any other forms of life. It causes no harm or good unless over-consumed. (1) The low abundance of aluminum in biology may be due to Al3+ being held in the lithosphere and/or organisms have evolved to lose Al3+. (mobilization)

Aluminum can be toxic to plants when the soil is acidic with a pH of 5 or below. Half of the world’s agricultural lands experience this acidity so aluminum is a limiting factor of a crop’s success. Plants can become resistant to Al by methods such as internal detoxification with carboxylate ligands or sequestration of Aluminum complexes. (physiology)

In a study on the translocation and transformation of Aluminum in the Calhoun Experimental Forest in South Carolina, an average annual uptake of Al was 2.28 kg/ha/year while the average annual accumulation in biomass off the ground was 0.48 kg/ha/year. Aluminum was found to not leach through the soil so the only method of removal was in the biomass. (silicon)

A metamorphic rock called emery that is mostly made of corundum which is an aluminum oxide. This is an example of an aluminum deposit.

Article Draft

References

1. Exley, Christopher. 2003. "A Biogeochemical cycle for aluminum?" Journal of Inorganic Biochemistry.
2. Markewitz, D., Richter, D.D. The Bio in Aluminum and Silicon Geochemistry. Biogeochemistry 42, 235–252 (1998). https://doi.org/10.1023/A:1005901417165
3. Kochian, L.V., Piñeros, M.A. & Hoekenga, O.A. The Physiology, Genetics and Molecular Biology of Plant Aluminum Resistance and Toxicity. Plant Soil 274, 175–195 (2005). https://doi.org/10.1007/s11104-004-1158-7
4. Pogue, Aileen I., and Walter J. Lukiw. “The Mobilization of Aluminum into the Biosphere.” Frontiers, Frontiers in Neurology , 24 Nov. 2014, https://www.frontiersin.org/articles/10.3389/fneur.2014.00262/full.