Kinetics and Mechanism of Ecochemical Processes

Kinetics and Mechanism of Ecochemical Processes

Sergey Olegovich Travin (Federal Research Center for Chemical Physics After N. N. Semenov of the Russian Academy of Sciences, Russia)
DOI: 10.4018/978-1-7998-1241-8.ch005

Abstract

Significant efforts of mankind and huge funds were spent to study the mechanisms of environmental processes. Recent decades have been marked by exponential growth of computer power and the accompanying decrease in the cost of computing. With regard to the mathematical modeling of physical and chemical processes that determine the quality of natural waters, atmosphere, and soil, this has led to the development of an extensive approach based on an increase in the number of components and reactions between them taken into consideration. In this chapter, the authors describe features of ecochemical systems and discuss the moments that complicates their prediction. Using the method of numerical experiment, they investigate the behavior of periodic systems with multiple stationary states. One conclusion is that the actual manifestation cannot be used to determine at what stage the impact occurred and to what stage of the food chain it relates. Another conclusion is that systems involving multiple stationary states are prone to bifurcations and chaotic jumps from one limit cycle to another.
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Introduction

“The main task of a chemist, as I imagine it, is the ability to predict and control the course of reactions. However, as with any other attempt of man to master the laws of nature, two approaches can be used. One is to create general theories, from which the consequences are deduced, concerning particular properties of matter. The second, based on empirical generalizations, builds partial and approximate theories that can explain the observed phenomena or suggest an interesting direction of experimental research. Because of the nature of our science, we, chemists, are forced to go mainly on the second way.”(Hammett, 1970). These words of L. Hammett are the best suited to the section of chemistry that is associated with the description of reactions in the atmosphere, natural waters and the earth's crust, i.e. to ecochemical processes.

Despite the rapid development of computer technology, the intensive penetration of mathematical modeling methods into practical chemical kinetics has minimally affected ecochemical systems. Indeed, the number of really theoretical works in which the deduction of the properties of the system is based on the first principles is extremely small. To such fundamental first principles, undoubtedly, we should include the law of mass action, the Arrhenius equation and the vast accumulated material on the rate and equilibrium constants of individual elementary stages. It would seem that this set of valuable information is directly intended for modeling and forecasting natural ecosystems, but a whole set of circumstances that distinguish natural processes from technological ones makes it difficult to describe them in detail.

Here are the main differences Let's enumerate the main differences between ecochemical processes and canonical ideas about how chemical reactions occur that are included in all the courses of chemical kinetics taught in universities.

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