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Elsy A. Escobar, Paul Dahlen and Paul C. Johnson School of Sustainable Engineering and the Built Environment Ari ona State Uni ersit Arizona State University Study transient vapor migration on a chemical-by- Study transient vapor

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Elsy A. Escobar, Paul Dahlen and Paul C. Johnson School of Sustainable Engineering and the Built Environment Ari ona State Uni ersit Arizona State University

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 Study transient vapor migration on a chemical-by-  Study transient vapor migration on a chemical by

chemical basis (i.e., time to reach steady-state), and its dependence on lithology

 Visualize steady-state soil gas profiles and quantify

mass emissions in idealized subsurface settings mass emissions in idealized subsurface settings

 Examine the difference between profiles and emissions

under conditions with and without oxygen

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 Allows more control of key variables and  Allows more control of key variables and

ability to create settings with known characteristics

 Easier to monitor the phenomena of interest  Can operate and monitor multiple sets of

conditions simultaneously

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Experimental Design: Experimental Design: Id Id li li d S b f S tti tti g Id Idea eali lize zed Subsur surface ace Setti ttings

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Experimental Experimental Set Set Up Set Set Up Up

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Chemical Experimental Mass Fraction n-Pentane 0.018 2-methyl-2-butene 0.011 MTBE 0 002 MTBE 0.002 n-Hexane 0.051 Benzene 0.005 Cyclohexane 0.059 n-Heptane 0.067 Toluene 0.038 p-xylene 0.043 Iso-Octane 0.100 n-Octane 0 056 n Octane 0.056 1,3,5-Trimethylbenzene 0.133 Mineral Oil 0.500 TOTAL 1.000

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Comparison of V Comparison of Vapor Source por Source Composition Composition to Weathered eathered Gasoline Gasoline Composition Composition to to Weathered athered Gasoline Gasoline

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0.45

Normalized Flux vs. Time Normalized Flux vs. Time Colu Column mn A: A: Sand Sand

0 25 0.30 0.35 0.40

d Flux, Flux,

air ir.C

.Ci,o

i,o/L)

/L)

0 10 0.15 0.20 0.25

rmalize

rmalized Ci/A)/(D /A)/(Di

0.00 0.05 0.10 5 10 15 20 25 30

No (Q. (Q.C

12 d 12 d 8 d 8 d

Time, days Time, days

N-Pentane 2-Methyl-2-Butene Benzene

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Near Near-Steady

Steady State T

State Times mes

Time, days Column Component y

A: Sand B: Sand – Crushed Granite

Sand

C: Sand - Crushed Granite D: Crushed Granite -Sand E: Crushed Granite –Sand - Crushed Granite F: Crushed Granite

n Pentane 8 22 23 11 9 31 n-Pentane 8 22 23 11 9 31 2-Methyl-2-Butene 8 27 29 14 9 39 MTBE 24 Transient state > 90 d Transient state > 130 d Transient state > 130 d 64 Transient state > 125 d n-Hexane 8 26 29 9 13 32 Benzene 12 Transient state > 83d 44 26 53 Transient state > 125 d Cyclohexane 8 31 24 16 13 32 y Iso-Octane 7 34 29 18 18 33 n-Heptane 9 27 Inconclusive 22 20 39 Toluene 30 Transient state > 90 d 85 26 Inconclusive Transient state > 125 d n-Octane 32 Transient state > 90 d Inconclusive Inconclusive 60 Inconclusive P-Xylene 47 Transient state > 90 d Transient state > 130 d Transient state > 130 d 71 Transient state > 125 d 1,3,5- Trimethylbenzene 92 Transient state > 90 d Transient state > 130 d Transient state > 130 d Transient state >130 d Transient state > 125 d

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Tr = R.v.L2/Deff

API (2005). A Practical Strategy for Assessing the

Expected Times vs. Experimental Times

R = (1+(m/Hi.v)+(Ki.b/v.Hi))

Subsurface Vapor-to-Indoor Air Migration Pathway at Petroleum Hydrocarbon Sites. Pub # 4741 Soil Properties

Deff = 0.0196 cm2/s rb = 1.68 g/cm3 fv = 0.32 cm3-vapor/cm3-soil fm = 0.04 cm3-water/cm3-soil fm 0.04 cm3 water/cm3 soil foc = 0.00043 g-oc/g-soil

Component Hi, LH2O/Lvapor Koc, L/Kg Ki =foc*Koc R Tr (calculated) , days Experimental time, days Column A Column A Colmn Colmn D Tr (calculated), days Experimental time, days , y

Pentane 41.15 1600 0.69 1.09 7.2 8 2-Methyl-2-Butene 3.55 156 0.067 1.13 7.5 8 MTBE 0.029 12.3 0.005 6.29 41.5 24 Hexane 58.13 4073.8 1.75 1.16 7.7 8

47.7 11 52.8 14 652.8 T 56.8 9 Benzene 0.18 58.9 0.025 2.43 16.0 12 Cyclohexane 6.14 482 0.21 1.20 7.9 8 Iso-Octane 107.27 2692 1.16 1.06 7.0 7 Heptane 78.07 2400 1.03 1.07 7.1 9 Toluene 0 21 259 0 11 4 32 28 5 30 210.5 26 61.3 16 43.4 18 45.1 22 457 8 26 Toluene 0.21 259 0.11 4.32 28.5 30 Octane 89.84 89.84 0.039 1.00 6.6 32 P-xylene 0.19 389 0.17 6.26 41.3 47

1,3,5-trimethylbenzene

0.24 1020 0.44 11.33 74.7 92 457.8 26 36.4 Inconclusive 709.0 T 1370.7 T

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0 40 0.45

r.C

.Ci,o

i,o/L)

/L)

Normal Normalized Flux Flux vs.

vs. Time

Time Colum Column A A

5 0 6.0

14 days 14 days

n-Pentane

Concentration Profiles Concentration Profiles

0.25 0.30 0.35 0.40

Q.C .Ci/A)/(D /A)/(Di

ai ai 1.0 2.0 3.0 4.0 5.0

Colum umn len n length, f th, ft n Pentane Benzene

0.05 0.10 0.15 0.20

zed Flux, ( zed Flux, (Q

0.0 1.0 0.0 0.2 0.4 0.6 0.8 1.0

C/C C/Co

0.00

20 40 60 80 100 120 140 160

Normali Normali

Time, days Time, days

4.0 5.0 6.0

gth, f th, ft

100 days 100 days

n-Pentane Benzene

N-Pentane 2-Methyl-2-Butene Benzene P-Xylene

0.0 1.0 2.0 3.0

Colu

lumn len

leng Benzene 0.0 0.2 0.4 0.6 0.8 1.0 C/ C/Co

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Column Mass Emission Rates [x10‐6 mg/cm2‐s] B: Sand‐ C: Sand‐ D: Crushed E: Crushed F: Crushed Components A: Sand Crushed Granite‐Sand Crushed Granite D: Crushed Granite‐Sand Granite‐Sand‐ Crushed Granite F: Crushed Granite n‐Pentane 3.8 0.79 1.9 4.3 12 1.7 2‐Methyl‐2‐Butene 0.72 0.13 0.47 0.68 2.7 0.28 MTBE 0.18 3.2 X 10‐5 0.010 0.008 0.099 0.003 n‐Hexane 0.85 0.09 0.33 0.55 2.2 0.19 Benzene 0.18 0.004 0.034 0.052 0.20 0.014 Cyclohexane 0.69 0.070 0.25 0.41 1.8 0.15 Iso‐Octane 0.62 0.055 0.18 0.38 1.5 0.11 n‐Heptane 0.41 0.031 0.13 0.21 1.0 0.058 Toluene 0.34 0.006 0.054 0.095 0.45 0.018 Toluene 0.34 0.006 0.054 0.095 0.45 0.018 Octane 0.10 0.004 0.021 0.033 0.19 0.005 P‐Xylene 0.097 Not detected 0.012 0.014 0.12 0.002 1,3,5‐ Trimethylbenzene 0.083 Not Detected 0.006 0.01 0.086 Not detected Trimethylbenzene

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4 0 5.0 6.0 th, ft th, ft

Column A Column A

n-Pentane B 5.0 6.0 , ft , ft

Column B Column B n-Pentane Benzene

0 0 1.0 2.0 3.0 4.0 Colum Column leng leng Benzene 1.0 2.0 3.0 4.0 Colum

lumn length

length

Benzene

0.0 0.0 0.2 0.4 0.6 0.8 1.0 C/Co C/Co 0.0 0.0 0.2 0.4 0.6 0.8 1.0 C C/Co C/Co Colum Column C C 4.0 5.0 6.0 gth, ft th, ft Colum Column D D n-Pentane Benzene 3.0 4.0 5.0 6.0 length, length, ft ft n-pentane Benzene 0 0 1.0 2.0 3.0 Colum Column len leng 0.0 1.0 2.0 Colum Column 0.0 0.0 0.2 0.4 0.6 0.8 1.0 C/Co C/Co 0.0 0.2 0.4 0.6 0.8 1.0 C/Co C/Co

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5.0 6.0 ft ft

Column F Column F

n-Pentane 5 0 6.0 ft

Column E Column E

n-Pentane 1.0 2.0 3.0 4.0 5.0

lumn Length Length, Benzene 1 0 2.0 3.0 4.0 5.0

lumn length, length, f Benzene 0.0 0.0 0.2 0.4 0.6 0.8 1.0 Co C/Co C/Co 0.0 1.0 0.0 0.2 0.4 0.6 0.8 1.0 Co C/Co C/Co

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 Transient data show that n-pentane, 2-methyl-2-butene, n-hexane,

l h i O d h i i il l d i k cyclohexane, iso-Octane and n-heptane migrate similarly and quickest as expected from theory.

 Transport times over a 2-m distance are days to weeks for these  Transport times over a 2 m distance are days to weeks for these

chemicals and months to years for other chemicals in the experiment.

 Soil gas profiles reflect the idealized subsurface setting in each

g p g column.

 These experiments provide a baseline to study aerobic biodegradation

ff t (i i i th th t f l ) effects (i.e., using air as the sweep gas across the top of column).

 Modeling of the experiment will be performed using the Luo (2009)

modification of the Johnson-Abreu mathematical model modification of the Johnson Abreu mathematical model.

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