Weathering of rocks and minerals

Clayton, J. L. (1986). An estimate of plagioclase weathering rate in the Idaho batholith based upon geochemical transport rates. In "Rates of Chemical Weathering of Rocks and Minerals" (S. M. Coleman and D. P. Dethier, eds). Chap. 19, pp. 453-466. Academic Press, New York. 

Lown, D. J. 1986. Controls on the rate of weathering and clay mineral genesis in airfall tephras a review and New Zealand case study. In Coleman, S. M. Dethier, D. P. (eds) Rates of Chemical Weathering of Rocks and Minerals. Academic Press, New York, 265-330. 

Aluminum, a silver-white, malleable, and ductile metal, is the most abundant metallic element in the lithosphere, comprising about 8% of the earth s crust. It is never found free in nature, but occurs combined with other elements, most commonly as aluminosilicates, oxides, and hydroxides in rock, minerals, clays, and soil. It is also present in air, water, and many foods. Bauxite, a weathered rock consisting primarily of aluminum hydroxide minerals, is the primary ore used in aluminum production. Aluminum enters environmental media naturally through the weathering of rocks and minerals. Anthropogenic releases are in the form of air emissions, waste water effluents, and solid waste primarily associated with industrial processes, such as aluminum production. Because of its prominence as a major constituent of the earth s crust, natural weathering processes far exceed the contribution of releases to air, water, and land associated with human activities. 

Miner 1969a). Barium enters the environment naturally through the weathering of rocks and minerals. Anthropogenic releases are primarily associated with industrial processes. Barium is present in the atmosphere, urban and rural surface water, soils, and many foods. 

Holdren G. R. and Speyer P. M. (1986) Stoichiometry of alkali feldspar dissolution at room temperature and various pH values. In Rates of Chemical Weathering of Rocks and Minerals (eds. S. E. Colman and D. P. Dethier). Academic Press, Orlando, pp. 61-81. 

Ivashov, P.V., 1971. The significance of biological factors in the weathering of rocks and minerals (in Russian). In A.S. Khomentovskiy (Editor), Biogeokhimiya Zony Giper-geneza. Nauka Press, Moscow, pp. 30—50. 

Nahon, D. (1986) Evolution of iron crusts in tropical landscapes. In Colman, S.M. Dethier, D.P. (Eds) Rates of Chemical Weathering of Rocks and Minerals. New York Academic Press, pp. 169-191. 

Humic substances constitute the bulk of the organic matter in most terrestrial soils. The functions they perform are multiple and varied and include the weathering of rocks and minerals, mobilization and transport of metal ions, and formation of stable aggregates by combination with clay minerals. Humic substances make a significant contribution to the cation-exchange capacity of the soil, and they are involved in the sorption of organic molecules applied to soils as pesticides. 

Rates of dissolution or weathering of rocks and minerals are proportional to their surface areas exposed to a given volume of solution, or rate a AIV). Exposed areas can vary widely, depending on the occurrence ol the rock. In this problem you are asked to compare and contrast the rates of rock dissolution under attack by acid rain and in the pores of a rock. We will assume that the rock, temperature, pressure, and solution chemistry are the same in both cases. 

Colman, S.M., and D.P,Dethier..laer. 1986. Rates of chemical weathering of rocks and minerals. Academic Press, NewYork.. I k. 

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