Elsy A. Escobar, Paul Dahlen and Paul C. Johnson School of - PowerPoint PPT Presentation

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 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

 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

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

Experimental Experimental Set Set Up Set Set Up Up

Experimental Chemical Mass Fraction n-Pentane 0.018 2-methyl-2-butene 0.011 MTBE MTBE 0 002 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 n-Octane 0 056 0.056 1,3,5-Trimethylbenzene 0.133 Mineral Oil 0.500 TOTAL 1.000

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

Normalized Flux vs. Time Normalized Flux vs. Time Colu Column mn A: A: Sand Sand 0.45 0.40 /L) i,o /L) Flux, d Flux, 0.35 .C i,o 0.30 ir .C air rmalized 0 25 0.25 a ormalize /A)/(D i C i /A)/(D 0.20 0.15 0 10 0.10 (Q.C No (Q. 0.05 8 d 8 d 12 d 12 d 0.00 0 5 10 15 20 25 30 Time, days Time, days N-Pentane 2-Methyl-2-Butene Benzene

Near- Steady Steady State T Near State Times mes Time, days y Column B: Sand – C: Sand - E: Crushed D: Crushed F: Crushed A: Sand Crushed Granite Crushed Granite –Sand - Granite -Sand Granite - Sand Granite Crushed Granite Component n-Pentane n Pentane 8 8 22 22 23 23 11 11 9 9 31 31 2-Methyl-2-Butene 8 27 29 14 9 39 Transient state Transient Transient state Transient MTBE 24 64 > 90 d state > 130 d > 130 d state > 125 d n-Hexane 8 26 29 9 13 32 Transient state Transient Benzene 12 44 26 53 > 83d state > 125 d Cyclohexane y 8 31 24 16 13 32 Iso-Octane 7 34 29 18 18 33 n-Heptane 9 27 Inconclusive 22 20 39 Transient state Transient Toluene 30 85 26 Inconclusive > 90 d state > 125 d Transient state n-Octane 32 Inconclusive Inconclusive 60 Inconclusive > 90 d Transient state Transient Transient state Transient P-Xylene 47 71 > 90 d state > 130 d > 130 d state > 125 d 1,3,5- Transient state Transient Transient state Transient state Transient 92 Trimethylbenzene > 90 d state > 130 d > 130 d >130 d state > 125 d

Expected Times vs. Experimental Times T r = R.  v .L 2 /D eff API (2005). A Practical Strategy for Assessing the Subsurface Vapor-to-Indoor Air Migration Pathway R = (1+(  m /Hi.  v )+(Ki.  b /  v .H i )) at Petroleum Hydrocarbon Sites. Pub # 4741 Soil Properties D eff = 0.0196 cm 2 /s r b = 1.68 g/cm 3 f v = 0.32 cm3-vapor/cm3-soil f m = 0.04 cm3-water/cm3-soil f m 0.04 cm3 water/cm3 soil f oc = 0.00043 g-oc/g-soil Column A Column A Colmn D Colmn Tr Tr H i, Ki Experimental Experimental Component LH 2 O/Lvapor K oc, L/Kg R (calculated) (calculated), =foc*Koc time, days time, days , days , y days y 8 Pentane 41.15 1600 0.69 1.09 7.2 47.7 11 2-Methyl-2-Butene 3.55 156 0.067 1.13 7.5 8 52.8 14 MTBE 0.029 12.3 0.005 6.29 41.5 24 652.8 T 8 Hexane 58.13 4073.8 1.75 1.16 7.7 56.8 9 Benzene 0.18 58.9 0.025 2.43 16.0 12 210.5 26 8 Cyclohexane 6.14 482 0.21 1.20 7.9 61.3 16 Iso-Octane 107.27 2692 1.16 1.06 7.0 7 43.4 18 9 Heptane 78.07 2400 1.03 1.07 7.1 45.1 22 Toluene Toluene 0.21 0 21 259 259 0 11 0.11 4 32 4.32 28 5 28.5 30 30 457.8 457 8 26 26 32 Octane 89.84 89.84 0.039 1.00 6.6 36.4 Inconclusive P-xylene 0.19 389 0.17 6.26 41.3 47 709.0 T 92 0.24 1020 0.44 11.33 74.7 1370.7 T 1,3,5-trimethylbenzene

Concentration Profiles Concentration Profiles Normal Normalized Flux Flux vs. vs. Time Time Colum Column A A /L) i,o /L) 14 days 14 days .C i,o 0.45 6.0 r .C n Pentane n-Pentane 0 40 0.40 5.0 5 0 t th, ft ai ai n length, f /A)/(D i Benzene .C i /A)/(D 4.0 0.35 umn len 3.0 0.30 2.0 Colum 0.25 Q.C 1.0 1.0 zed Flux, (Q 0.20 C zed Flux, ( 0.0 0.15 0.0 0.2 0.4 0.6 0.8 1.0 0.10 C/C C/Co 0.05 100 days 100 days Normali Normali 0.00 0 20 40 60 80 100 120 140 160 6.0 n-Pentane th, ft 5.0 Time, days Time, days gth, f 4.0 Benzene Benzene leng olumn len N-Pentane 2-Methyl-2-Butene Benzene P-Xylene 3.0 2.0 Colu 1.0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 C/ C/Co

Mass Emission Rates [x10 ‐ 6 mg/cm 2 ‐ s] Column B: Sand ‐ C: Sand ‐ E: Crushed D: Crushed D: Crushed F: Crushed F: Crushed A: Sand Crushed Crushed Granite ‐ Sand ‐ Granite ‐ Sand Granite Granite ‐ Sand Granite Crushed Granite Components 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 Toluene 0.34 0.34 0.006 0.006 0.054 0.054 0.095 0.095 0.45 0.45 0.018 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 ‐ 0.083 Not Detected 0.006 0.01 0.086 Not detected Trimethylbenzene Trimethylbenzene

Column A Column A Column B Column B 6.0 6.0 n-Pentane n-Pentane 5.0 th, ft th, ft 5.0 , ft , ft Benzene Benzene 4.0 4 0 Benzene B olumn length length Column leng leng 4.0 3.0 3.0 2.0 Colum 2.0 Colum 1.0 1.0 0 0 0.0 C 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 C/Co C/Co C/Co C/Co Column C Colum C 6.0 Colum Column D D n-pentane 5.0 6.0 ft length, ft Benzene n-Pentane length, 4.0 5.0 gth, ft th, ft Benzene 3.0 4.0 leng Column Column len 3.0 Colum 2.0 2.0 Colum 1.0 1.0 0.0 0 0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 C/Co C/Co C/Co C/Co

Column E Column E Column F Column F 6.0 6.0 n-Pentane n-Pentane 5.0 5.0 ft ft ft 5.0 5 0 length, f Length, Benzene lumn length, lumn Length Benzene 4.0 4.0 3.0 3.0 2.0 2.0 olum olum 1.0 1 0 1.0 Co Co 0.0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 C/Co C/Co C/Co C/Co

 Transient data show that n-pentane, 2-methyl-2-butene, n-hexane, cyclohexane, iso-Octane and n-heptane migrate similarly and quickest l h i O d h i i il l d i k 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 effects (i.e., using air as the sweep gas across the top of column). ff t (i i i th th t f l )  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.