Geological systems mixing

Example 9.15 Long-term asymptotic solution of reversible reaction diffusion systems The formation of dynamic reaction-diffusion fronts occurs when two species A and B are uniformly distributed on opposite sides of an impenetrable barrier, which is removed at time t 0 at isothermal conditions. The species A and B start to diffuse and react upon mixing, and produce species C. This creates a dynamic reaction front, and the spatio-temporal evolution of this front may exhibit some unique features, which may be valuable in understanding many phenomena in physical, chemical, biological, and geological systems. The long-term behavior of this reversible reaction-diffusion system was studied by Koza (2003). 

T. S. Bowers and H. C. Helgeson, Calculation of the Thermodynamic and Geochemical Consequences of Nonideal Mixing in the System H2O-CO2-NaCl on Phase Relations in Geologic Systems Equation of State for H2O-CO2-NaCl Fluids at High Pressures and Temperatures, Geochim. Cosmochim. Acta, 47, 1247-1275 (1983). 

Bowers, T.S., and Helgeson, H.C., 1983, Calculation of the thermodynamic and geochemical consequences of nonideal mixing in the system H20-C02-NaCl on phase relations in geologic systems Geochim. Cosmochim. Acta., v. 47, pp. 1247-1275. 

Another desirable attribute of a waste classification system that is a corollary of the system being risk-based is that it treat wastes that pose similar health risks consistently. A chemically hazardous waste estimated to pose a certain risk should be in the same waste class as a radioactive waste that poses an equivalent risk, and similarly for mixed waste. Consistency also implies that wastes posing similar risks could be disposed of using essentially the same technology (municipal/industrial landfill, licensed near-surface facility for hazardous waste, or geologic repository). 

In measurements of dissolved sulfate in rivers, the fact that flowing water may not readily mix laterally or vertically has often been ignored. For example, the Mackenzie and Liard rivers of northern Canada were found to require a distance of the order of 400 km below their confluence before lateral mixing was achieved (Krouse and Mackay, 1971). In another study of this same river system, Hitchon and Krouse (1972) used chemical data and factor analyses to relate qualitatively large variations in the sulfur isotope compositions of dissolved sulfate to a number of geological sources, despite the fact that biological activity had probably altered both the concentrations and ratios. 

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