General form of the ADE:

sink/source term

Chemical sink/source term

t

ccq

x

cv

x

cD

ss

2

2

Simple form of the ADE

Uniform 1D flow; longitudinal dispersion;sink/source term

General form of the ADE:

sink/source term

Chemical sink/source term

We will consider two types of chemical reactions

1. Sorption (adsorption & absorption)

2. 1st order irreversible reactions (radioactive decay,

hydrolysis, some forms of biodegradation)

(Zheng & Bennett)

LEA

sorption 1st order

Zheng & Bennett, Fig. 4.3

= v/vc

Sorption (or retardation)

R > 1

= v/vc

Zheng & Bennett, Fig. 4.3

Zheng & Bennett, Fig. 4.2

Linear Isotherm

LEA (Local Equilibrium Assumption)

Linear Isotherm

from MT3DMS manual

t

cR

cq

x

cv

x

cD

ss

2

2

Simple form of the ADE

Uniform 1D flow; longitudinal dispersion;sink/source term; retardation

Retardation Factor

t

c

R

cq

x

c

R

v

x

c

R

D ss

2

2

Simple form of the ADE

= vc

R = v/vc

Zheng & Bennett, Fig. 4.2

Linear Isotherm

Freundlich Isotherms

Unlimited sorption sites

Freundlich Isotherm

Langmuir Isotherm

Limited sorption sites

= maximum sorption capacity

Langmuir Isotherm

Spitz and Moreno (1996)

fraction of organic carbon

Spitz and Moreno ( 1996)

General form of the ADE:

Chemical sink/source term

Zheng & Bennett

dbKR

1

linear

We will consider two types of chemical reactions

1. Sorption (adsorption & absorption)

2. 1st order irreversible reactions (radioactive decay,

hydrolysis, some forms of biodegradation)

t

cRRc

cq

x

cv

x

cD

ss

2

2

Simple form of the ADE

Uniform 1D flow; longitudinal dispersion;sink/source term; retardation; 1st orderirreversible reaction ( is the same for thedissolved phase and the sorbed phase)

1st order rate constant= ln 2 / half life = 0.693/ t½

Zheng & Bennett