Modeling of Vapor Intrusion and Volatile Organic Compounds...

Modeling of Vapor Intrusion and Volatile

Organic Compounds Transport in the Soil – Review and Implementation

Xinyue Liu

Exchange student from South University of Science and Technology in China

CONTENTS

1 Conceptual model

3 Numerical model

2 Mathematical model

4 Results and discussion

5 Next step

1 Conceptual model

Some of the volatile organic compounds,

contained in contaminants of interest from

the subsurface, can enter the building

through soil gas transportation.

Vapor intrusion

Johnson, P. C., & Ettinger, R. A. (1991). Heuristic model for predicting the intrusion rate of contaminant vapors into buildings.

1 Conceptual model

• Sources: gas station, improper disposal,

accidental spillage, or leaking landfill liners

• Forms: can become bound to the soil matrix,

dissolved in groundwater (or soil water)

and/or exist as a separate, residual phase

known as a non-aqueous phase liquid

(NAPL)

• Two broad categories: chlorinated solvents

and petroleum hydrocarbons.

VOC contaminants

Johnson, P. C., & Ettinger, R. A. (1991). Heuristic model for predicting the intrusion rate of contaminant vapors into buildings.

1 Conceptual model

• Slab

• Crawl space

• Basement

Buildings

Yao, Y., Shen, R., Pennell, K. G., & Suuberg, E. M. (2013). A Review of Vapor Intrusion Models.

2 Mathematical model

1. Darcy’s law:

Governing equations

2. Convection-diffusion equation:

3. Millington and Quirk equation:

2 Mathematical model

1. Darcy’s law:

Boundary conditions

p=0

p=0

p=0

p=0

p=-5 [Pa]

p=0 p=0

Water table

symmetric infinity

atmosphere

slab

crack

slab

16 m * 3 m domain

3 Numerical model

• Comsol:

Simulation software;

especially for Multiphysics problems

• 229 codes:

Created by MIT Course 229 Staffs

1. Darcy’s law:

• parameters:

ϕg (air filled porosity) = 0.38

Kg (permeability) = 1e-12 [m^2]

3 Numerical model

• 229 codes:

1. Darcy’s law:

3 Numerical model

• 229 codes:

• Finite volume method

1. Darcy’s law:

Pierre F.J Lermusiaux. Lecture 15 notes

1

*

.

.

Nx Ny

p

p

p

=

( ) 0p

c pt

− =

( ) 0p

x y c p ndAt

− =

( ) ( ) 0face

faces

px y c p n A

t

− =

d pAp

dt=

CDS approximation

FV discretization of

Laplace operator

3 Numerical model

• 229 codes:

• Finite volume method

1. Darcy’s law:

Pierre F.J Lermusiaux. Lecture 15 notes

d pAp

dt=

FV discretization of

Laplace operator - Dfs

1 23 4_

2

n n nnp p p

Dfs p Dfs bcst

− −− += +

4 Results and discussion

• Pressure field:

• Time = 20 h

• Comsol:

• 229 codes:

4 Results and discussion

• Pressure field:

3 Numerical model

2. Convection-diffusion equation:

3. Millington and Quirk equation:

Advection of gasAdvection of water

Diffusion Reaction

Gas phase Liquid

phase

Solid

phase

Effective transport

porosity

Effective diffusion

coefficient

Gas

phase

Liquid

phase

chlorinated solvents

Porosity n = 0.38

Diffusion coefficient Di<0.01cm2/s

3 Numerical model

• Comsol:

2. Convection-diffusion equation:

3. Millington and Quirk equation:

Advection of gasAdvection of water

Diffusion Reaction

Gas phase Liquid

phase

Solid

phase

Gas

phase

Liquid

phase

3 Numerical model

• Comsol: Boundary conditions

c=0

c=1

c=0

c=0

c=0 c=0

Water table

symmetric infinity

atmosphere

slab

crack

slab

16 m * 3 m domain

4 Results and discussion

• Comsol:

4 Results and discussion

• Comsol:

T = 300h

T = 500h

Vapor intrusion

Path way is complete

T = 900h

Vapor intrusion becomes steady;

Risk maximum

References

[ 1 ] P i e r r e F. J L e r m u s i a u x . 2 2 9 L e c t u r e n o t e s

[ 2 ] J o h n s o n , P. C . , & E t t i n g e r , R . A . ( 1 9 9 1 ) . H e u r i s t i c m o d e l f o r p r e d i c t i n g t h e

i n t r u s i o n r a t e o f c o n t a m i n a n t v a p o r s i n t o b u i l d i n g s . E n v i r o n m e n t a l S c i e n c e &

Te c h n o l o g y, 2 5 ( 8 ) , 1 4 4 5 - 1 4 5 2

[ 3 ] Ya o , Y. , S h e n , R . , P e n n e l l , K . G . , & S u u b e r g , E . M . ( 2 0 1 3 ) . A R e v i e w o f

Va p o r I n t r u s i o n M o d e l s . E n v i r o n m e n t a l S c i e n c e & Te c h n o l o g y, 4 7 ( 6 ) , 2 4 5 7 -

2 4 7 0 .

[ 4 ] Ya o , Y. , S h e n , R . , P e n n e l l , K . G . , & S u u b e r g , E . M . ( 2 0 1 3 ) . A R e v i e w o f

Va p o r I n t r u s i o n M o d e l s . E n v i r o n m e n t a l S c i e n c e & Te c h n o l o g y, 4 7 ( 6 ) , 2 4 5 7 -

2 4 7 0 . d o i : 1 0 . 1 0 2 1 / e s 3 0 2 7 1 4 g

[ 5 ] I l l a n g a s e k a r e , T. ; P e t r i , B . ; F u č i k , R . ; S a u c k , C . ; S h a n n o n , L . ; S m i t s , K . ;

C i h a n , A . ; C h r i s t , J . ; S c h u l t e , P. ; P u t m a n , B . ; L i , Y. Va p o r I n t r u s i o n f r o m

E n t r a p p e d N A P L S o u r c e s a n d G r o u n d w a t e r P l u m e s : P r o c e s s U n d e r s t a n d i n g a n d

I m p r o v e d M o d e l i n g To o l s f o r P a t h w a y A s s e s s m e n t , S E R D P P r o j e c t E R - 1 6 8 7

F i n a l R e p o r t 2 0 1 4 .

Q&A?

Thank you: Pier re F.J Lermusiaux (MIT) ;

Wael Haj j Al i (MIT) ;

Enze Ma (SUSTech)