Geochemistry/geochemical kinetics

This chapter provides a general discussion of kinetics versus thermodynamics, chemical kinetics versus geochemical kinetics, and an overview of the basics of various kinetic processes and applications. Subsequent chapters will provide in-depth development of theories and applications of specific subjects. The purpose of the overview in this chapter is to provide the big picture of the whole field before in-depth exploration of the topics. Furthermore, this chapter is a standalone chapter that may be used in a general geochemistry course to introduce kinetics to students. 

In this chapter we consider the problem of the kinetics of the heterogeneous reactions by which minerals dissolve and precipitate. This topic has received a considerable amount of attention in geochemistry, primarily because of the slow rates at which many minerals react and the resulting tendency of waters, especially at low temperature, to be out of equilibrium with the minerals they contact. We first discuss how rate laws for heterogeneous reactions can be integrated into reaction models and then calculate some simple kinetic reaction paths. In Chapter 26, we explore a number of examples in which we apply heterogeneous kinetics to problems of geochemical interest. 

Reaction kinetics enter into a geochemical model, as we noted in the previous chapter, whenever a reaction proceeds quickly enough to affect the distribution of mass, but not so quickly that it reaches the point of thermodynamic equilibrium. In Part I of this book, we considered two broad classes of reactions that in geochemistry commonly deviate from equilibrium. 

In this chapter, we consider how to construct quantitative models of the dynamics of microbial communities, building on our discussion of microbial kinetics in Chapter 18. In our modeling, we take care to account for how the ambient geochemistry controls microbial growth, and the effect of the growth on geochemical conditions. 

Strombkrg, B. Banwart, S. A. 1994. Kinetic modelling of geochemical processes at the Aitik mining waste rock site in northern Sweden. Applied Geochemistry, 9, 583-595. 

Langmuir, D., and J. Mahoney. 1985. Chemical equilibrium and kinetics of geochemical processes in ground water studies. In Practical applications of ground water geochemistry, Proc. 1st Canadian/American con/, on hydrogeology, ed B. Hitchon and E. I. Wallick, pp. 69-95. Worthington, OH Natl. Water Well Assoc. 

Geochemical modeling. 2. Chemical kinetics. 3. Geochemistry-Mathematical models. I. Title. 

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Burnham AK, Sweeney JJ (1989) A chemical kinetic model of vitrinite maturation and reflectance. Geochem Cosmochim Acta 53 2649-2657 Carothers WW, Kharaka YK (1978) Aliphatic acid anions in oil-field waters - implications for the origin of natural gas. Am Assoc Pet Geol Bull 62 2441-2453 Constantinides G, Arich G (1967) Non-hydrocarbon compounds in petroleum. In Nagy B, Colombo U (eds) Fundamental aspects of petroleum geochemistry. Elsevier, New York, pp 77-108... 

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