Assessment of the Behavior of Chemical Warfare Agents in Landfills

S.L. Bartelt-Hunt, M.A. Barlaz D.R.U. Knappe, P. Kjeldsen

Dept. of Civil, Construction, & Environmental Engineering North Carolina State University Project Motivation z A chemical and/or biological attack on a building in the U.S. may result in a large amount of contaminated debris that would require disposal z There is little information on the behavior of chemical and biological agents in a landfill Objectives z Model the distribution and behavior of chemical agents in a landfill z Determine which fate routes are most important z Determine sensitivity of results to model input parameters z Bounding calculations to guide experimental work MOCLA Model for Organic Chemicals in Landfills

solid (fs)

Kd KH

Fa FD

Soil Cover gas (fa)

Waste water (fw) Transformation (Fλ) Fw LCS Fdiff Modified from Kjeldsen and Christensen (2001) MOCLA: Input Parameters

Chemical Parameters •Henry’s law constant (dimensionless)

•Log Kow •Dair •Dwater • Abiotic half-life

• Biotic half-life (λbiotic = ∞) Evaluation of Chemical Fate Prior to Disposal Toxic Industrial Chemicals • Carbon disulfide, furan will be included in bounding calculations • others judged to volatilize prior to landfilling (e.g. ethylene oxide, phosgene) Evaluation of Chemical Fate Prior to Disposal

Blister Agents

Distilled Mustard (HD) Lewisite (L) All blister agents will be Nitrogen Mustard (HN-2) included in bounding Phosgene Oxime (CX) calculations Ethyldichloroarsine (ED) Evaluation of Chemical Fate Prior to Disposal Nerve Agents

Cyclohexyl Sarin (GF) Sarin (GB) All nerve agents will be Soman (GD) included in bounding Tabun (GA) calculations VE Amiton (VG) VM VX Tear Gas (CS) Properties of Chemical Agents1 Sulfur Mustard Chemical VX Furan (HD)

Chemical Formula C4H8Cl2S C9H26NO2PS C4H4O CAS number 505-60-2 50782-69-9 110-00-9 Molecular weight (g/mol) 159.07 267.4 68.08 Boiling point (°C) 218 292 31.4 Freezing point (°C) 14.45 <-51 -85.6 Vapor pressure (mm Hg) 0.11 0.0007 600 Henry's Law constant 9.8×10-4 1.4×10-7 2.2×10-1 (dimensionless)

Log Kow 2.41 2.09 1.34 Hydrolysis half-life (min) 8.5 24,480-60,480 infinite Aqueous solubility (mg/L) 684 30,000 1×104 9 pK - - a (tertiary amine)

1 Data at 25 °C unless otherwise stated 2N.A. = Not Available O

+ O H HO-P-O-C2H5 + (CH3)2NH H3C N-P-O-C2H5 CN Ethylphosphoryl Dimethylamine H3C CN cyanidate GA

- OH O H3C GA (Tabun) - + N-P-O-C2H5 +CN+ H H C 3 OH O-Ethyl N,N-dimethylamido Cyanide hydrolysis phosphoric acid pathway O H3C N-P-OH H C 3 OH Dimethylphosphoramidate

O HO-P-OH OH Phosphoric acid Cl-CH2-CH2-S-CH2-CH2-Cl Sulfur Mustard

H2O -Cl-

CH2 H O CH2-CH2-Cl H O CH2-CH2-OH + 2 2 Cl-CH2-CH2-S S S CH -CH -OH CH -CH -OH CH2 2 2 2 2 Mustard Sulfonium ion Hemimustard Thiodiglycol Gas (HD)

Thiodiglycol Thiodiglycol H2O -Cl- hydrolysis + + CH2-CH2-S -(CH2-CH2-OH)2 CH2-CH2-S -(CH2-CH2-OH)2 S H2O S CH2-CH2-Cl CH2-CH2-OH Sulfur Mustard-thiodiglycol Hemimustard-thiodiglycol pathway aggregate aggregate

Thiodiglycol -Cl- H2O CH -CH -S+-(CH -CH -OH) S 2 2 2 2 2 + CH2-CH2-S -(CH2-CH2-OH)2 Sulfur Mustard-thiodiglycol- thiodiglycol aggregate MOCLA: Input Parameters

Base- Parameter Units Range Source case Assumed average wet bulk Dry bulk density of density (700-1200 lb/yd3) and mT/m3 0.34 - 0.63 0.49 the waste(ρb) moisture content of waste (10-20% wet weight basis) Assumed average wet bulk Volumetric moisture density (700-1200 lb/yd3) and content of the waste m3 water/m3 LF 0.042 - 0.14 0.091 moisture content of waste (ε ) w (10-20% wet weight basis) Volumetric gas Assumed values based on content of the waste m3 air/m3 LF 0.10 - 0.40 0.25 data from Bendz (1997) (εa) Fraction of organic 0.40 - 0.60 0.5 Barlaz (1998) carbon in waste (foc) Height of waste (H) m 18.3 - 61 39.7 Assumed range of 60-200 ft MOCLA: Input Parameters Base- Parameter Units Range Source case Precipitation and Net precipitation (N) leachate generation data arid climate m/yr 0.02 - 0.05 0.04 from Landfill Life-cycle (sites with < 20 inch/yr) Inventory Report (EREF 2000) Precipitation and Net precipitation (N) leachate generation data wet climate m/yr 0.04 - 0.32 0.12 from Landfill Life-cycle (sites with > 20 inch/yr) Inventory Report (EREF 2000) -kt qa = 2WLoke where Lo Gas production rate (q ) varies from 85-170 L a m3 LFG/m3 LF yr 1.9 - 3.7 2.8 arid region methane/kg wet waste and k is 0.02 yr-0 -kt qa = 2WLoke where Lo Gas production rate (q ) varies from 85-170 L a m3 LFG/m3 LF yr 4.5 - 9.0 6.75 wet region methane/kg wet waste and k is 0.05 yr-1 MOCLA: Input Parameters Cover soil

Base- Parameter Units Range Source case

Thickness of Cover Soil U.S. EPA Subtitle D m 0.45 (L) regulation

Total porosity of Cover unitless 0.30 - 0.50 0.4 Assumed values Soil (εsc)

Gravimetric moisture % (dry weight 10.3 -30.8 20.0 Benson (1999) content basis) Dry bulk density of the g/cm3 1.3 - 2.0 1.7 Benson (1999) cover soil MOCLA: Input Parameters Liner

Base- Parameter Units Range Source case

U.S. EPA Subtitle Thickness of liner m 0.6 D regulation

Total porosity of liner 0.30 - 0.50 0.4 Assumed values

Gravimetric moisture % (dry weight 10.3 - 30.8 20.0 Benson (1999) content basis) Dry bulk density of the g/cm3 1.3 - 2.0 1.7 Benson (1999) liner MOCLA Simulations Simulation type Climate Variable Base-case scenario arid as a function of time time = 6 mo, 1 yr, 5 yr, 30 yr (no biological wet decay) Base-case scenario (1 yr) with biotic wet λbiotic = ∞, 1000,100, 10 d degradation Monte Carlo wet λ = ∞ simulations biotic Hydrolysis products (1 yr base case wet λ = ∞ simulations) Results: Equilibrium Phase Fractions

1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 ) ) X lfide GE GF V VG VM CS Furan Lewisite GB (Sarin) fs (solid) GA (Tabun)GD (Soman Mustard (HD fw (leachate) Carbon disu ed Nitrogen Mustard Phosgene Oxime Ethyldichloroarsine fa (gas) Distill Results: Base-case scenario

1.00 0.80 Fλ abiotic 6 month 0.60 simulation: 0.40 Fa 0.20 arid climate Fraction remaining 0.00

e n d te e ) E F G id ra r si rin) G G V CS u a i im a VX VM F (HD) w x oman) d ust e O Tabun S M L e ( loroarsine A GB (S ustar en G GD ( M sgen rog ho Carbon disulf it P N Ethyldich istilled D 1.00 0.80 Fλ abiotic 0.60 6 month 0.40 Fa simulation: 0.20 0.00 Fraction remaining wet climate e n ) te e e E D rd i n) an) G GF VG ta is sin im bu m VX VM lfid Fura (H s w r x isu rd O d Le roa e (Ta (So n sta n Mu o n GB (Sarin)D chl GA G rbo ge i osge Mu h Ca d itro yld P N Eth istille D Results: Base-case scenario

1.00

0.80 Fλ abiotic 5 year 0.60 0.40 Fa

simulation: 0.20 arid climate 0.00 Fraction remaining

d e e n) n) sit me un) a GE GF VG M CS fide uran tar i i ari VX V ul F rsin S ew a Ox Tab ( Som dis L ( ( n loro ene A GB D o h G G b osg rogen Mus ldic h Car t P Ni thy E Distilled Mustard (HD)

1.00 0.80 Fλ abiotic 0.60

5 year 0.40 Fa simulation: 0.20 wet climate 0.00 e ) n ) ite e n) E F G Fraction remaining rd im u G G VX V VM CS ura ta is sin x F s O (Tab Mu Lew roar lo ene GB (Sarin n g GA ge ich GD (Soman) Carbon disulfide itro Phos N Ethyld Distilled Mustard (HD Results: Base-case scenarios

1.00

0.80 Fλ abiotic 30 year 0.60 0.40 simulation: Fa arid climate 0.20 0.00 Fraction remaining ) e e n) it an) ran s m ari GE GF VX VG VM CS Fu (HD arsine abun) S om Lewi ro T S stard lo GB ( en Mustard g GA ( GD ( Mu ro hosgene Oxi Carbon disulfideed P Nit till Ethyldich Dis

1.00 0.80 Fλ abiotic 30 year 0.60 0.40 simulation: 0.20 Fa wet climate 0.00 ) n ) te e e ) ide an GE GF VG M CS ura tard isi im m VX V lf F (HD w rsin x Fraction remaining isu d us a So d M Le e O B (Sarin) ( star en G D bon sg GA (Tabun G r Mu ldichloroo Ca d itrogen Ph ille N thy st E Di Impact of Climate

0.50

0.40

0.30

0.20

Fraction remaining 0.10

0.00

n de a VX VG VM CS lfi ur isu F Wet scenario d n o rb Arid Scenario a C 10X Wet Scenario Persistence of select CWAs

1.0 CS furan

g 0.8 CX GD

0.6 VX

0.4

Fraction remainin Fraction 0.2

0.0 0 5 10 15 20 25 30 Time (yr) Results: Effects of biodegradation

λbiotic= ∞λbiotic= 1000 d 1.0 1.0 0.9 0.9 0.8 0.8

n 0.7 n 0.7 0.6 0.6 0.5 0.5 0.4 0.4 CWA fractio CWA fractio 0.3 0.3 0.2 0.2 0.1 0.1 0.0 0.0 HD HN-2 GB GD VX furan HD HN-2 GB GD VX furan λbiotic= 100 d 1.0 λbiotic= 10 d 1.0 0.9 0.9 0.8 0.8

n 0.7 n 0.7 0.6 0.6 0.5 0.5 0.4

CWA fractio 0.4 0.3 fractio CWA 0.3 0.2 0.2 0.1 0.1 0.0 0.0 HD HN-2 GB GD VX furan HD HN-2 GB GD VX furan Fraction remaining in the landfill Fraction transformed via biodegradation

1.0

Fraction transformed0.0 via abiotic hydrolysis Fraction transported via gas phase advection Findings z All CWAs are predominantly associated with the solid phase in the landfill due to high log Kow values z Significant fate routes are abiotic hydrolysis and gas phase advection z Blister agents (HD, HN-2, ED, L) and some G- agents (GA and GB) are transformed quickly (~6 months) z VX, GD, CS and toxic industrial chemicals persist in landfill for 5 yr or longer Findings z Effect of climate is minimal

z Slight increase in Fa (advective loss) due to increase in gas production rate z No effect on abiotic hydrolysis rate z Decreasing biotic half-life to 10 days impacts fate only for compounds with long abiotic hydrolysis half- lives relative to the simulation period z Knowledge of fate of hydrolysis products is critical Uncertainty Analysis z Performed using Crystal Ball (Excel add-in) z Triangular distribution used for all input parameters z Employed Latin Hypercube sampling with 1000 realizations z Scenario: 1 year simulation, wet climate, no biological degradation Results: Uncertainty Analysis

1 1 GD y 0.8 0.8 GB 0.6 0.6 0.4 0.4

Probabilit 0.2 0.2 0 0 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1

Fλ, abiotic Fλ, abiotic 1 1 1 0.8 VX HN-2 Furan

y 0.8 0.8 0.6 0.6 0.6 0.4 0.4 0.4

Probabilit 0.2 0.2 0.2 0 0 0 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 00.20.40.60.81 Fλ, abiotic Fλ, abiotic Fa

CPD for HD is a vertical line at Fλ, abiotic = 1 Results: Uncertainty Analysis

Contribution to CWA Fate Pathway MOCLA input parameter Variance

gas production rate (qa) 71.4% gas-phase furan K 16.0% advection H waste bulk density (ρb) -6.0% λ -83.7% HD abiotic hydrolysis abiotic waste moisture content (εw) 6.8% λ -84.7% HN-2 abiotic hydrolysis abiotic waste moisture content (εw) 7.2% λ -88.9% GB abiotic hydrolysis abiotic waste moisture content (εw) 7.1%

λabiotic -80.4%

GD abiotic hydrolysis waste moisture content (εw) 10.3%

log Kow -4.9% λ -87.7% VX abiotic hydrolysis abiotic waste moisture content (εw) 8.0% Findings: Uncertainty Analysis z Greatest degree of uncertainty in results for GD and VX z Difference in simulation results under uncertainty for GD compared to GB is attributable to longer abiotic half-life of

GD combined with higher log Kow value z VX results are attributable to uncertainty associated with longer hydrolysis half-life (29.5 d) z Abiotic half-life accounts for greater than 80% of variance in model predictions Fate of Hydrolysis Products

Agent Hydrolysis Product Scenario: 1 Distilled Mustard Thiodiglycol (TDG) year base- (HD) case simulation, 2-(2-chloroethyl) Nitrogen Mustard wet climate, (NH-2) methylamino ethanol no degradation VX EA2192 (abiotic or biotic) Results: Hydrolysis Products Equilibrium phase fractions

Phase fractions CWA Hydrolysate

fa fw fs

TDG 0.000 0.255 0.745

2-(2-chloroethyl) methylamino ethanol 0.000 0.213 0.787

EA2192 0.000 0.189 0.811 Results: Hydrolysis Products

Fate routes

Compound Fraction F a F (diffusion) F remaining (advection) a w

Thiodiglycol (TDG) 0.991 0.000 0.000 0.008

2-(2-chloroethyl)- methylamino ethanol 0.992 0.000 0.000 0.007

EA2192 0.993 0.000 0.000 0.006 Findings: Hydrolysis Products z Equilibrium phase fraction results for all hydrolysates indicates chemical present in leachate fraction (lower log Kow) z All hydrolysis products remain in landfill at end of 1 year simulation z Fw could be significant pathway for CWA hydrolysis products z Information on biotic and/or abiotic degradation of hydrolysis products is critical Acknowledgements z US EPA Safe Buildings Program z Susan Thorneloe and Paul Lemieux