PUBLICATIONS--Release of the report "Modification of a method-of-characteristics solute-transport model 

In Reply Refer To:                                  June 6, 198
WGS-Mail Stop 411


Subject:        PUBLICATIONS--Release of the report "Modification of a
                        method-of-characteristics solute-transport
                        model to incorporate decay and
                        equilibrium-controlled sorption or ion
                        exchange" by Daniel J. Goode and Leonard
                        F. Konikow

This subject report has recently been released as Water-Resources
Investigations Report 89-4030.  The report documents modifications
made to the two-dimensional ground-water solute-transport model of
Konikow and Bredehoeft (1978, TWRI

Book 7, Chapter C2).  These modifications enable simulation of
three types of chemical reactions:  (1) first-order irreversible
rate reaction, such as radioactive decay (2) reversible
equilibrium-controlled sorption with linear, Freundlich, or
Langmuir isotherms and (3) reversible equilibrium-controlled ion
exchange for monovalent or divalent ions.

These processes are incorporated in the general solution scheme
that uses method-of-characteristics with particle tracking for
advection and finite-difference methods for dispersion.  The first
type of reaction is accounted for by an exponential decay term
applied directly to the particle concentration.  The second and
third types of reactions are incorporated through a retardation
factor, which is a function of concentration for nonlinear cases.
The model is evaluated and verified by comparison with analytical
solutions for linear sorption and decay, and by comparison with
other numerical solutions for nonlinear sorption and ion exchange.

The report is being sent under separate cover to District, State,
and some Subdistrict Offices of the Water Resources Division.  The
computer program is available on the Software Exchange System
(SOFTEX), from the National Water Information System (NWIS)
Program Office, or from the authors.

                               Eugene P. Patten
                               Chief, Office of
                               Ground Water

WRD Distribution:  A, B, S, FO, PO