Oxigeno Y Medidores

Wat. Res. Vol. 25, No. 5, pp. 499-528, 1991 Printed in Great Britain. All rights reserved

0043-1354/91 $3.00 + 0.00 Copyright © 1991 Pergamon Press pie

REVIEW PAPER SORPTION PHENOMENA IN SUBSURFACE SYSTEMS: CONCEPTS, MODELS A N D EFFECTS ON CONTAMINANT FATE A N D TRANSPORT*
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WALTER J. WEnER JR "~', PAUL M. MCGINLEY a n d LYNN E. KATZ ~) Environmental and Water Resources Engineering,The University of Michigan, Ann Arbor, MI 48109, U.S.A.

(First received March 1990; accepted in revised form September 1990)
Abstract--The behavior, transport and ultimate fate of contaminants in subsurface environments may be affected significantly by their participation in sorption reactions and related phenomena. The degree to which the resulting effects can be quantified and predicteddepends upon the extent to which certain fundamental aspects of sorption are understood, and upon the accuracy with which these phenomena can be characterized and modeled in complex subsurface systems. Current levels of understanding of the reactions and processes comprising sorption phenomena are discussed in this paper, as are the forms and utilities of different models used to describe them.Emphasis is placed on concept development, on the translation of these concepts into functional models for characterizing sorption rates and equilibria, and on the application of these concepts and models for explaining contaminant behavior in subsurface systems. Examples are provided to illustrate the impacts of sorption phenomena on contaminant transport.

Key words--sorption, partitioning, soils,groundwater, subsurface systems, rate and equilibrium models, mass transfer, contaminant tranport

NOMENCLATURE A = area (L 2) a~ = chemical activity of species i b -- Langmuir isotherm coefficient corresponding to the enthalpy of adsorption (L3/M) C~,~= equilibrium solution phase concentration of species i (M/L 3) C * = equilibrium solution phase concentration of species ¢,1 i in a singie-solutesystem at the same spreading pressure as that of a mixture (M/L ~) C,.: -- concentration of species i associated with phase or interface j (M/L 3) D, = effective diffusion coefficient (L2/t) Dh = hydrodynamic dispersion coefficient (L2/t) Dh -- second-rank hydrodynamic dispersion tensor (L2/t) D~,a = apparent dispersion coefficient (L2/t) D1 = free liquid diffusion coefficient (L2/t) D m = minimumenergy in the Morse potential model (ML2/t 2) E = C o u l o m b i c constant of proportionality (ML3/

F-Q 3)

o = minimum energy level for attractive forces in Lennard-Jones potential (ML2/t 2) f, j = activity coefficient of species i in phase j F~,'~ = flux of species i in direction x (M/L2-t) HSA =hydrocarbonaceous molecular surface area (L 2) k = Boltzman's constant 1,38 x 10-~serg/degree Kelvin (ML:/F-T) *This paper was the basis of the 1990 Distinguished Lecture by Walter J. Weber Jr for the Association of Environmental Engineering Professors. 499

k ' = psuedo-first-order rote constant (I/t) K~ = ion-exchange selectivity coefficient between ions A and B k~ = overall mass transfer coefficient for diffusion into an adjacent solute accumulating phase (l/t) K D = distributioncoefficient (L3/M) K{~ = distribution coefficient in phase j(L~/M) k¢ = effective mass transfer coefficient (L/t) K~ = equilibrium constant K F = Freundlich isotherm constant [(L~/M) ~] k F = forward rate constant (L3/M-t) kf = film transfer coefficient (L/t) Ko¢ -- organic carbon-normalized linear isotherm coefficient (L3/M) Kow = octanol/water partition coefficient (dimensionless) Kp--partitioncoefficient (dimensionsless) k R = reverse rate constant (l/t) m = Morse potential constant (l/L) N = total number of species in solution n = Freundlich isotherm exponent (dimensionless) %OC = percent soil organic carbon content q = mass of solute sorbed per unit mass of sorbent (M/M) q, -- mass of solute sorbed per unit mass of sorbent at radial distance r (M/M) qo,~= mass of solute i sorbed per...