Weathering environments

Review in Chapter 2, WEATHERING/ ENVIRONMENT, Weather Resistance. 

Weathering Many plastics has short lives when exposed to outdoor conditions. The better materials include acrylic, chlorotri-fluorethylene, vinylidene fluoride, chlorinated polyether, polyester, alkyd, and black linear poly-ethylene. Black materials are best for outdoor service. Some of the styrene copolymers are suitable for certain outdoor uses (Chapter 2, WEATHERING/ ENVIRONMENT). 

Dove, P. (1995). Kinetic and thermodynamic controls on silica reactivity in weathering environments. In "Chemical Weathering Rates of Silicate Minerals" (A. F. White and S. L. Brantley, eds), Mineralogical Society of America Washington, DC, Reviews in Mineralogy 31, 235-290. 

Johnsson, M. J., Stallard, R. F., and Lundberg, N. (1991). Controls on the composition of fluvial sands from a tropical weathering environment Sands of the Orinoco River drainage basin, Venezuela and Colombia. Geol. Soc. Am. Bull. 103,1622-1647. 

Stallard RF, Edmond JM (1983) Geochemistry of the Amazon. 2. The influence of geology and weathering environment on the dissolved load. J Geophys Res 88(C14) 9671-9688... 

Weathering environments cycle of sulfur in, 26 30 Weathering, of inorganic pigments, 19 382, 383... 

Gray, D.J. 1998. The aqueous chemistry of gold in the weathering environment. CSIRO Division of Exploration Geoscience, Perth, Restricted Report EG4R, 65 pp. (Reissued as Open File Report 38, CRC LEME, Perth, 1998). 65. 

Tipper et al. (2006) have measured the Mg isotope composition of rivers. They observed a total variation in Mg of 2.5%c. The lithology in the drainage area seems to be of limited significance, a major part of the variability has to be attributed to fractionations in the weathering environment. 

Nico, P. S. Fendorf, S. E. Eowney, Y. W. Holm, S. E. Ruby, M. V. Chemical Structure of Arsenic and Chromium in CCA-Treated Wood Implications of Environmental Weathering. Environ. Sci. Technol. 2004, 38, 5253-5260. 

The omnipresence of aluminium in weathering environments results in most of the Fe oxides in soils, except lepidocrocite, being Al-substituted. The possible range of substitution as deduced from synthesis experiments (see Chap. 3) viz. up to Al/ (Fe Al) of ca. 0.33 in goethite and up to Al/(Fe Al) of ca. 0.16 in hematite is also found in soil goethites and hematites. Where the two oxides coexist on a small scale... 

Lumpkin, G. R. Mariano, A. N. 1996. Natural occurrence and stability of pyrochlore in carbona-tites, related hydrothermal systems, and weathering environments. In Murphy, W. M. Knecht, D. A. (eds) Scientific Basis for Nuclear Waste Management XIX. Materials Research Society Symposium Proceedings, 412, 831-838. 

The use of chemical modelling to predict the formation of secondary phases and the mobility of trace elements in the CCB disposal environment requires detailed knowledge of the primary and secondary phases present in CCBs, thermodynamic and kinetic data for these phases, and the incorporation of possible adsorp-tion/desorption reactions into the model. As noted above, secondary minerals are typically difficult to identify due to their low abundance in weathered CCB materials. In many cases, appropriate thermochemical, adsorption/desorp-tion and kinetic data are lacking to quantitatively describe the processes that potentially affect the leaching behaviour of CCBs. This is particularly tme for the trace elements. Laboratory leaching studies vary in the experimental conditions used (e.g., the type and concentration of the extractant solution, the L/S ratio, and other parameters such as temperature and duration/ intensity of agitation), and therefore may not adequately simulate the weathering environment (Rai et al. 1988 Eary et al. 1990 Spears Lee, 2004). 

The geological environments which form clay minerals can be basically divided into five types weathering, sedimentation, burial, diagenetic and hydrothermal alteration. The weathering environment frequently presents a chemical system where T,P are constant and many chemical elements are mobile, usually they enter solution from the rocks present at the earth s surface through the process of hydrolysis. The major problems are (a) Determination of rates of reaction among the minerals present,... 

In sum, one can say that 14 8 trioctahedral brucitic chlorite is largely unstable in most weathering environments, but aluminous soil chlorites are common under acid conditions. The bulk of chlorite found in sediments is certainly detrital in origin. 7 and 14 8 chlorites can be formed from 50°C upward in temperature until above 100°C where 14 8 chlorite becomes one of the most common minerals in sedimentary rocks. 

From the above observations, it is certain that corrensite is a mineral which will form in normal sedimentary rocks and weathering environments. Thus it will be stable throughout the full range of clay mineral physical environments. It forms in sedimentary rocks which contain important quantities of iron (divalent) or magnesium but is not necessarily related to evaporite deposits and thus alkaline conditions of formation. 

The initial increase in hydrostatic pressure in a sedimentary basin appears not to change mineral stabilities from those of the weathering environment. The formation of potassic, iron-rich micas such as ferric illite and glauconite both in lacustrine and shallow ocean basins demonstrates their stability at low pressures and temperatures. The same is true of the 7 8 chlorite chamosite or berthierine. Most likely the chemical variables of pH, Eh and the activity of the various ions in solution are predominant in silicate phase equilibria in sedimentary environments. 

Kittrick, J.A. MontmorilIonite equilibria and the weathering environment. Soil Sci. Soc. Amer. Proc. 35, 815-820 (1971). 

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