FUNDAMENTAL-ASPECTS OF QUANTITATIVE MODELS FOR GEOCHEMICAL CYCLES

The modern treatment of geochemical cycles requires a truly quantitati ve framework. This paper addresses various aspects of such quantificat ion. The concepts of residence time and response time are reviewed. Th e important concept of mass balance in geochemical cycles and its dyna mical implications are discussed, with particular stress on the need f or feedbacks in the carbon cycle. Particular emphasis is also placed o n understanding the behavior of non-linear systems. The use of new and more encompassing global rate laws in models of geochemical cycles re quires that (a) proper attention be given to the statistical averaging and extrapolation involved in constructing the particular sets of cyc le reservoirs (for trample, the flux of river water to the sea) and (b ) that the knowledge about the fundamental physical chemical and biolo gical processes operating within reservoirs and giving rise to fluxes between reservoirs be incorporated into any global dynamics. As an exa mple of the latter, the problem of rates of dissolution during weather ing is presented to illustrate the importance of knowing mere about th e surface properties and reactivities of minerals. (C) 1998 Published by Elsevier Science B.V. All rights reserved.