EPA/600/R-17/186 August 2017
www.epa.gov/homeland-security-research
United States
Environmental Protection
Agency
oEPA
Natural Attenuation of the Persistent
Chemical Warfare Agent VX on
Porous and Permeable Surfaces
Office of Research and Development
National Homeland Security Research Center
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EPA/600/R-17/186
August 2017
Natural Attenuation of the Persistent
Chemical Warfare Agent VX on Porous and
Permeable Surfaces
U.S. Environmental Protection Agency
Office of Research and Development
National Homeland Security Research Center
Research Triangle Park, NC 27711
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Disclaimer
The U.S. Environmental Protection Agency, through its Office of Research and Development,
funded and managed the research described here under Contract Number EP-C-11-038, Task
Order 23 with Battelle. It has been subjected to the Agency's review and has been approved for
publication. Note that approval does not signify that the contents necessarily reflect the views of
the Agency. Mention of trade names, products, or services does not convey official EPA
approval, endorsement, or recommendation.
Questions concerning this document or its application should be addressed to the principal
investigator:
Lukas Oudejans, Ph.D.
National Homeland Security Research Center
Office of Research and Development
U.S. Environmental Protection Agency (MD-E343-06)
109 T.W. Alexander Drive
Research Triangle Park, NC 27711
Phone: 919-541-2973
Fax: 919-541-0496
E-mail: Oudeians.Lukas@epa.gov
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Acknowledgments
This effort was initiated following discussions with the U.S. Environmental Protection Agency's
(EPA's) Office of Land and Emergency Management (OLEM)'s Office of Emergency
Management (OEM) and EPA Regional On-Scene Coordinators on high-priority research needs
to support response and recovery following incidents involving chemical, biological, or
radiological (CBR) agents or materials. This work was managed by the principal investigator
from Office of Research and Development (ORD)'s National Homeland Research Center
(NHSRC) with input from US EPA project team members:
Lukas Oudejans, Ph.D. (Principal Investigator), ORD/NHSRC
Paul Lemieux. Ph.D., ORD/NHSRC
Lawrence Kaelin, OLEM/OEM/Consequence Management Advisory Division (CMAD)
Catherine Young, EPA Region 1
Charlie Fitzsimmons, EPA Region 3
Brian Englert, EPA Region 4
This effort was completed under U.S. EPA contract EP-C-11-038, Task Order 23, with Battelle;
the research efforts of the following Battelle personnel are greatly appreciated:
David Chappie
David See
Anthony Ellingson
Zachary Willenberg
Robert Lordo
The authors would like to acknowledge Joan Bursey for her technical editing; QA reviewers
Ramona Sherman and Eletha Brady-Roberts; and reviewers Emily Parry (ORD/NHSRC) and
David Bright (OEM/CMAD) for their contributions to this report.
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Table of Contents
Disclaimer v
Acknowledgments vi
Acronyms and Abbreviations x
Executive Summary xii
1.0 Introduction 1
1.1 Purpose 1
1.2 Proj ect Obj ectives 1
1.3 Test Facility Description 2
2.0 Experimental Methods 3
2.1 General Experimental Design 3
2.2 Test Matrices 4
2.3 Test Chamber 6
2.4 Test Materials 7
2.5 Chemical Agent and Spiking Coupons 8
2.6 Extraction of VX from Coupons 9
2.7 Extraction Recovery Method Demonstration 9
2.8 Analytical Methods 11
2.8.1 Analysis for VX 11
2.8.2 Analysis for VX Hydrolysis Product 13
2.9 Analysis of Variance (ANOVA) to Test Hypotheses 15
3.0 Test Results 19
3.1 Extraction Recovery Method Demonstration Results 19
3.2 Natural Attenuation Results 21
3.2.1 Environmental Condition 1 21
3.2.2 Environmental Condition 2 27
3.2.3 Environmental Condition 3 33
3.3 ANOVA Results 38
4.0 Quality Assurance/Quality Control 42
4.1 Control of Monitoring and Measuring Devices 42
4.2 Equipment Calibrations 43
4.3 Technical Systems Audit 45
4.4 Performance Evaluation Audit 45
4.5 Data Quality Audit 46
4.6 Deviations 46
5.0 Summary 48
6.0 References 52
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List of Figures
Figure ES-1. Percent of VX attenuated over time versus material and temperature (negative VX
attenuation reflects instances when higher VX was recovered from the test coupons than
the associated spike controls) xiii
Figure 1. Photograph of coupons associated with the extraction recovery method demonstration
showing use of round Petri dishes and square acrylic boxes 10
Figure 2. VX recoveries following coupon extraction in various solvents (error bars equal plus one
standard deviation) 19
Figure 3. Photograph of silanized glass coupon with VX having a "pancake" appearance 23
Figure 4. Photograph of silanized glass coupon with VX having a "spread" appearance 23
Figure 5. VX recovery at Environmental Condition 1 (error bars equal plus one standard deviation).
Initial VX amount is 2200 (ig 24
Figure 6. VX recovery at Environmental Condition 2 (error bars equal plus one standard deviation).
Initial spiked VX amount is 1900 (ig except for plywood (2100 (ig) 30
Figure 7. VX recovery at Environmental Condition 3 (error bars equal plus one standard deviation).
Initial spiked VX amount is 2100 (ig except for plywood (2200 (ig) 35
Figure 8. Percent of VX attenuated overtime by material and temperature (negative VX attenuation
reflects instances when higher VX was recovered from the test coupons than the
associated spike controls) 49
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List of Tables
Table ES-1. Weathering Period (Time) when at Least 90% VX Attenuation was First Observed* xiv
Table 1. Natural Attenuation Test Matrix and Coupons Used for Each Material Type 5
Table 2. Description of Materials Used for the Natural Attenuation Investigation 7
Table 3. Gas Chromatography/Mass Spectrometry Conditions 12
Table 4. VX Recoveries from Materials Extracted Using Different Solvents (all with IS) 20
Table 5. Observations Associated with Environmental Condition 1* across Replicates 22
Table 6. VX Recovery at Environmental Condition 1 25
Table 7. EMPA Degradation Product Recovery at Environmental Condition 1* 26
Table 8. Relative Humidity during Environmental Condition 2 Testing 28
Table 9. Observations Associated with Environmental Condition 2* across Replicates 29
Table 10. VX Recovery at Environmental Condition 2 31
Table 11. VX Recoveries from Silanized Glass at 7, 14, and 21 Days at Environmental Condition 2 32
Table 12. EMPA Degradation Product Recovery at Environmental Condition 2* 33
Table 13. Observations Associated with Environmental Condition 3* across Replicates 34
Table 14. VX Recovery at Environmental Condition 3 36
Table 15. EMPA Degradation Product Recovery at Environmental Condition 3* 37
Table 16. ANOVA Test Results for Mean Rate of VX Loss (Slope Estimate) from Different
Materials (among the Three Environmental Conditions Tested) 40
Table 17. ANOVA Test Results Identifying Pairs of Materials with Significantly Different Mean
Residual Mass under Identified Environmental Conditions 41
Table 18. Quality Control Requirements and Results 42
Table 19. Equipment Calibration Schedule 44
Table 20. Gas Chromatography Performance Parameters and Acceptance Criteria 45
Table 21. Performance Evaluation Results 46
Table 22. Percent of VX Naturally Attenuated over Time by Environmental Condition 50
Appendices
Appendix A. VX Analysis by GC/MS, Sample Chromatograms 53
Appendix B. Relative Humidity during Environmental Conditions 1 and 2 testing 55
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Acronyms and Abbreviations
%R
percent recovery
°C
degree(s) Celsius
ANOVA
analysis of variance
CBR
chemical, biological, and radiological
CCV
continuing calibration verification
cm
centimeter(s)
CMAD
Consequence Management Advisory Division
CV
coefficient of variation
CWA
chemical warfare agent
D1
diethyl methylphosphonate (degradation product of EMPA)
D2
diethyl dimethylpyrophosphonate (degradation product of EMPA)
DIC
N,N'-diisopropylcarbodiimide
EMPA
ethyl methylphosphonic acid
EPA
U.S. Environmental Protection Agency
FID
flame ionization detector
FOD
frequency of detection
GC
gas chromatography
GLM
general linear model
HDPE
high density polyethylene
HMRC
Hazardous Materials Research Center
HS
Homeland Security
HSRP
Homeland Security Research Program
INL
Idaho National Laboratory
IS
internal standard
kHz
kilohertz
LED
light-emitting diode
Hg
microgram(s)
|iL
microliter(s)
|im
micrometer(s)
min
minute(s)
mL
milliliter(s)
mm
millimeter(s)
MS
mass spectrometer(try)
NHSRC
National Homeland Security Research Center
NIST
National Institute of Standards and Technology
OEM
Office of Emergency Management
OLEM
Office of Land and Emergency Management
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ORD
Office of Research and Development
PB
procedural blank
PTFE
polytetrafluoroethylene
QA
quality assurance
QAPP
quality assurance project plan
r2
coefficient of determination
RH
relative humidity
SD
standard deviation
TSA
technical systems audit
UV
ultraviolet
VX
O-ethyl S-(2-[diisopropylamino]ethyl) methylphosphonothioate
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Executive Summary
The U.S. Environmental Protection Agency (EPA) Homeland Security Research Program's
(HSRP's) purpose is to protect human health and the environment from adverse impacts,
including those resulting from acts of intentional contamination (including terrorist incidents) by
investigating the effectiveness and applicability of remediation technologies for environmental
response. Within the HSRP, EPA's National Homeland Security Research Center (NHSRC)
conducts research needed to identify methods and equipment that can be used for
decontamination of building surfaces contaminated with chemical warfare agents (CWAs).
Previous research has indicated that natural attenuation might be an effective, low cost option for
surfaces contaminated with CWAs, especially given the relatively high volatility of some of
these agents. For example, natural attenuation of CWAs such as O-ethyl S-(2-
[diisopropylaminojethyl) methylphosphonothioate (VX) occurs following deposition onto
relatively nonporous materials (EPA, 2016). A further study was undertaken to determine the
applicability of using natural attenuation of a persistent CWA on porous or permeable materials.
This project studied the influence of temperature on the natural attenuation of VX from five
types of porous/permeable materials: unsealed concrete, plywood, rubber escalator handrail, high
density polyethylene (HDPE) plastic, and acoustic ceiling tile. Natural attenuation of VX was
also measured on silanized glass, which served as a nonporous reference material. Testing was
conducted at three different temperatures (25 degrees Celsius [°C], 10 °C, and 35 °C). Other
environmental conditions such as relative humidity (RH) at 40% and air exchange (one air
exchange per hour) were held constant during the testing. The test durations lasted 28 days at 25
°C, 35 days at 10 °C, and 10 days at 35 °C.
Material coupons of 4.0 centimeters (cm) x 2.5 cm were each spiked with 2 microliters (|iL) of
neat VX. After weathering periods (ranging from 30 minutes [min] to 35 days), VX was
extracted from the coupons and quantified via gas chromatography (GC)/mass spectrometry
(MS).
The natural attenuation of VX was estimated by:
Mean VX Attenuated (%) = 100% - Mean VX Recovered (%),
relative to spike controls by material, temperature,
and weathering period.
Natural attenuation measured the reduction in the amount of extractable VX remaining following
unaided degradation or volatilization of VX from the spiked materials. The attenuation estimates
did not distinguish between VX losses attributed to volatilization, degradation, or inability to be
extracted from spiked materials. VX attenuation results are shown in Figure ES-1.
As shown in Figure ES-1, natural attenuation of VX occurred on all six materials under all three
temperatures tested. Natural attenuation of VX tended to occur faster at warmer temperatures.
For example, at least 90% attenuation on all materials occurred within seven days at 35 °C and
within 28 days at 25 °C. At 10 °C, less than 80% VX attenuation occurred on rubber escalator
handrail, high density polyethylene (HDPE) plastic, and ceiling tile after 35 days (the longest
duration tested).
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-20
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34
Extraction Time (Weathering Period) in Days
Figure ES-1. Percent of VX attenuated over time versus material and temperature (negative VX attenuation reflects instances
when higher VX was recovered from the test coupons than the associated spike controls).
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Natural attenuation was also influenced by the material tested. In general, VX attenuation
occurred fastest on unsealed concrete (possibly associated with the inherently low VX extraction
efficiencies from this material), plywood, and silanized glass. VX attenuation was slower on
rubber escalator handrail, HDPE plastic, and ceiling tile. Table ES-1 shows the times that at least
90% VX attenuation was first observed for several materials and environmental conditions (test
temperatures).
The natural attenuation of VX achieved >90% for all materials at all three temperatures, except
the rubber escalator handrail, HDPE plastic, and ceiling tile at 10 °C, which all achieved only
>70% attenuation. Despite the high levels of VX attenuation, non-detect results for all material
replicates occurred for only plywood and silanized glass after a 28-day weathering period at 25
°C and a 10-day weathering period at 35 °C.
Semi-quantitative analysis for VX-associated hydrolysis product ethyl methylphosphonic acid
(EMPA) confirmed VX degradation on some materials with time. This degradation product is
considered to be relatively non-toxic. However, it does provide insight on the degradation of VX
in addition to the evaporation process. The detection of other VX degradation products including
highly toxic EA-2192 was not attempted because such an analysis would require the use of liquid
chromatography/MS, which was beyond the scope of this study.
Table ES-1. Weathering Period (Time) when at Least 90% VX Attenuation was First
Observed*
Material
Environmental Condition
1 (25 °C)
Actual VX
,,ime, Attenuation
(days) (%)
2(10 °C)
Actual VX
,,ime, Attenuation
(days* (%)
3 (3
Time
(days)
5 °C)
Actual VX
Attenuation
(%)
Unsealed concrete
2
91
14
94
1
91
Plywood
4
94
21
93
2
96
Rubber
escalator handrail
28
91
>35f
75*
7
92
HDPE plastic
14
97
>351'
79t
7
99
Ceiling tile
14
93
>35f
77t
7
97
Silanized glass
7
94
35
99.7
3
91
* Coupons were extracted at eight time points (weathering periods) ranging from 30 min to 35 days; the time points
differed for each of the enviromnental conditions. The minimum time required to achieve 90% VX attenuation may
be lower.
t 90% VX attenuation was not achieved at the longest weathering period tested, which is identified as the actual
VX attenuation is provided for the longest available weathering period.
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Impact of the Study:
Based on the results obtained from this investigation, natural attenuation of persistent CWAs
such as VX applied to porous/permeable materials occurs given sufficient time (days to several
weeks). Natural attenuation was found to occur faster at warmer temperatures. Natural
attenuation was also influenced by material type, with faster attenuation occurring on unsealed
concrete, plywood and silanized glass. Slower VX attenuation occurred on rubber escalator
handrail, HDPE plastic, and ceiling tile. Relatively poor extraction efficiencies of VX from
unsealed concrete limits the interpretation of the natural attenuation of VX as it is not determined
whether residual VX is still present in unsealed concrete. This investigation was conducted using
clean and newly fabricated surfaces (except for the concrete). Aged materials and the presence of
dirt, grime or other (nontoxic) chemicals may enhance or reduce the persistence of VX while the
absence of ultraviolet (UV) light limits the findings of this study to indoor settings.
Trace amounts of VX may still be present weeks to months after a contamination event. These
amounts should be put into context with surface concentration cleanup goals for VX. EPA has
not established cleanup objectives such as surface cleanup levels. Such cleanup levels are
expected to be site-specific and likely to be at or below the detection limit for VX (by GC/MS) in
this study. Therefore, detectable amounts of VX on these materials, even after weeks of natural
attenuation, would require surface or volumetric decontamination/neutralization to reach the
expected cleanup level. The amount of VX observed on procedural blanks should be interpreted
to indicate that volatilization of VX results in a redistribution of some of the VX onto originally
clean surfaces; however, observed amounts were low and were also declining with time.
Clearance sampling following the implementation of natural attenuation as a decontamination
strategy should also consider the analysis of VX degradation products, some of which were
detected in this investigation, and some of which may have significant toxicological effects
themselves. In some instances, (e.g., unsealed concrete after 10 days [all environmental
conditions] and ceiling tile after seven hours [all environmental conditions]), there was no visible
evidence of VX on the surface of the material, but VX was generally detected via extractive
sampling methods. The potential adsorption or embedding of VX into porous or permeable
materials should also be taken into consideration when selecting surface sampling methods and
decontamination approaches to reach acceptable surface concentrations.
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1.0 Introduction
The U.S. Environmental Protection Agency's (EPA's) Homeland Security Research Program
(HSRP) serves to protect human health and the environment from the adverse impacts of a
chemical, biological, or radiological (CBR) agent release. The HSRP's role is to develop tools
and information that will help detect and quantify the intentional release of CBR contaminants in
buildings, water systems, or the outdoor environment; contain these contaminants;
decontaminate buildings, water systems or the outdoor environment; and facilitate the treatment
and disposal of hazardous materials resulting from remediation/cleanup activities.
As part of the HSRP, EPA's National Homeland Security Research Center (NHSRC)
investigates the effectiveness and applicability of technologies and/or approaches for homeland
security (HS)-related applications by developing test plans that are responsive to the needs of the
HSRP's EPA Program Office and Regional partners, conducting tests, collecting and analyzing
data, and preparing peer-reviewed reports. EPA NHSRC provides high-quality information that
is useful to decision makers in responding to incidents and implementing appropriate
technologies to mitigate consequences to the public resulting from CBR incidents.
U.S. EPA is responsible for planning for and responding to releases of toxic chemicals into the
environment, including the deliberate release of chemical warfare agents (CWAs). EPA (EPA,
2016) previously reported that natural attenuation of O-ethyl S-(2-[diisopropylamino]ethyl)
methylphosphonothioate (VX) occurs following deposition onto relatively nonporous materials.
Natural attenuation might provide a low cost and low impact approach for decontaminating
surfaces and may also be a desirable option for structures that do not require immediate
reopening/reoccupation. Further study was needed to determine the applicability of using natural
attenuation for decontamination of CWAs from porous/permeable materials. This project
evaluated the natural attenuation of VX after being applied as a liquid onto porous/permeable
materials.
1.1 Purpose
The purpose of this project was to measure the rate and magnitude of natural attenuation of VX
from various porous or permeable materials after application as a liquid at different temperatures
to better inform potential decontamination options for less volatile CWAs.
1.2 Project Objectives
The project objective was to evaluate natural attenuation of VX from various porous or
permeable materials including unsealed concrete, plywood, rubber escalator handrail, high
density polyethylene (HDPE) plastic, and ceiling tile. Natural attenuation of VX was also studied
on silanized glass, which served as a nonporous reference material similar to the previous study
that investigated the natural attenuation of VX from nonporous materials (EPA 2016). Testing
was conducted for 28 days at 25 degrees Celsius (°C), 35 days at 10 °C, and 10 days at 35 °C.
During testing, the relative humidity (RH) was maintained at nominal 40%, and the air exchange
rate was held at one volume of test chamber air per hour.
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1.3 Test Facility Description
All testing was performed at the Battelle Hazardous Materials Research Center (HMRC) located
on the Battelle site in West Jefferson, Ohio. The HMRC is certified to work with chemical surety
material through its Bailment Agreement W911SR-10-H-0001 with the U.S. Department of the
Army.
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2.0 Experimental Methods
As a general overview, multiple coupons (small representative pieces) of various materials were
simultaneously challenged (spiked) with neat VX for the natural attenuation investigation. All of
the spiked coupons were placed in a test chamber under controlled temperature, RH, and air
exchange conditions. At designated times, groups of coupons were removed from the chamber,
extracted, and analyzed for VX, leaving the remainder of the coupons in the chamber for further
exposure and later analysis. More specific experimental methods are provided in Sections 2.1
through 2.8.
2.1 General Experimental Design
A multiple group time-series experimental design was used, as represented below:
Xi
Oio
On
O12
Ol3
Ol4
Ol5
Ol6
Ol7
X2
O20
O21
O22
023
024
025
O26
027
X3
O30
O31
O32
033
034
035
036
037
For this experimental design, time passes from left to right. For n=l, 2, 3, Xn represents the
experimental treatment (X) performed within a specified environmental condition (n). Coupons
were randomly assigned to groups that were extracted and analyzed for VX after up to eight time
durations (t) within the specified environmental condition. The mean masses of VX (five
replicates) recovered from coupons for a given material after a given time (t) under a given
environmental condition (n) were the experimental results/observations (Ont).
Three hypotheses were tested:
Test #1:
• Null hypothesis: No decline occurs in mean recovered VX over time.
• Alternative hypothesis: Mean recovered VX declines over time.
Test #2:
• Null hypothesis: The mean rate of VX loss does not change among different
environmental conditions (temperatures).
• Alternative hypothesis: The mean rate of VX loss differs among environmental
conditions (temperatures).
Test #3:
• Null hypothesis: The mean rate of VX loss does not vary among different materials.
• Alternative hypothesis: The mean rate of VX loss does vary among different materials.
Each statistical test was performed by applying an analysis of variance (ANOVA) to the log-
transformed residual masses of VX. The ANOVA model assumed an exponential decay over
time and included effects for the duration of time from spiking to the measurement of residual
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mass (i.e., eight distinct time points, treated as continuous time measurements), material type,
temperature, and interactions between these terms (as they were deemed statistically significant
at the 0.05 level). Each hypothesis test was associated with a test for a specific parameter in the
ANOVA model:
• Test #1: Test for whether the slope parameter associated with time from initial spiking is
significantly less than 0 (i.e., results in a decline in the mass measurement with increasing
time).
• Test #2: Test for whether the slope parameter (rate of decline) differs significantly
among different environmental conditions (temperatures).
• Test #3: Test for whether the slope parameter (rate of decline) differs significantly among
different materials.
For a specific statistical test within the ANOVA, the null hypothesis was rejected for the
alternative hypothesis if the p-value for the F-test performed on the given model parameter was
no higher than 0.05.
2.2 Test Matrices
The test matrix for VX natural attenuation is shown in Table 1. Between attenuation tests, the
test chamber and work area were cleaned, and contaminated test items and waste were disposed
of. Attenuation was evaluated under controlled temperature, RH, and air exchange rates in a
custom-built test chamber. Briefly, the natural attenuation investigation was conducted as
follows:
• Six materials (five porous/permeable and one nonporous) were used for the attenuation
investigation. The five porous/permeable materials were unsealed concrete, plywood,
rubber escalator handrail, HDPE plastic, and ceiling tile. The nonporous material
(silanized glass) was used as a reference material that would generally reflect the amount
of VX attenuated via volatilization.
• Testing was conducted at three environmental conditions; each was run as a separate test
in the chamber:
o Environmental Condition 1: 25 ± 3 °C, 40 ± 5% RH, with one chamber volume of
air exchanged per hour. Testing performed for 28 days.
o Environmental Condition 2: 10 ± 3 °C, 40 ± 5% RH, with one chamber volume of
air exchanged per hour. Testing performed for 35 days.
o Environmental Condition 3: 35 ± 3 °C, 40 ± 5% RH, with one chamber volume of
air exchanged per hour. Testing performed for 10 days.
• Environmental conditions in the chamber (with coupons present) were stabilized at
specified experimental conditions for at least 24 hours prior to spiking coupons.
• On the first day of each test, 40 coupons of each material type were spiked with 2
microliters (|iL) of VX as described in Section 2.5. Coupons were spiked in the test
chamber. In addition, 2 |iL of VX was spiked directly into hexane (five replicates) and
acetone (five replicates) at time zero to serve as spike controls. The spike controls were
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spiked evenly throughout the time zero spiking operation (i.e., one prior to spiking
samples, one after every two weathering time sets, and the last following the spiking of
all samples). Solvent volumes for the spike controls we identical to the extraction volume
for the material coupons, namely, 25 mL.
Table 1. Natural Attenuation Test Matrix and Coupons Used for Each Material Type
Environmental
Conditions
Materials Tested
Initial Analyses
(Coupons Per
Each Material)
Seven Additional
Time Points
(Coupons Per Each
Material)
Condition 1:
25 °C, 40% RH,
with one chamber
volume of air
exchanged per
hour
Unsealed concrete*,
Plywood,
Rubber escalator
handrail,
HDPE plastic,
Ceiling tile*,
Silanized glass
5 spike controls (no coupons);
5 test coupons, 1 procedural blank, 1
laboratory blank (30 min after spike);
3 breakthrough controls (for unsealed
concrete and ceiling tile only, used
throughout all time points)^
5 test coupons,
1 procedural blank,
1 laboratory blank
(extraction time points:
7 hours; 1, 2, 4, 7, 14
and 28 days after
spike)
Condition 2:
10 °C, 40% RH,
with one chamber
volume of air
exchanged per
hour
Unsealed concrete*,
Plywood,
Rubber escalator
handrail,
HDPE plastic,
Ceiling tile*,
Silanized glass
5 spike controls (no coupons);
5 test coupons, 1 procedural blank, 1
laboratory blank (30 min after spike);
3 breakthrough controls (for unsealed
concrete and ceiling tile only, used
throughout all time points)^
5 test coupons,
1 procedural blank,
1 laboratory blank
(extraction time points:
7 hours; 1, 4, 7, 14, 21,
and 35 days after
spike)
Condition 3:
35 °C, 40% RH,
with one chamber
volume of air
exchanged per
hour
Unsealed concrete*,
Plywood,
Rubber escalator
handrail,
HDPE plastic,
Ceiling tile*,
Silanized glass
5 spike controls (no coupons);
5 test coupons, 1 procedural blank, 1
laboratory blank (30 min after spike);
3 breakthrough controls (for unsealed
concrete and ceiling tile only, used
throughout all time points)^
5 test coupons,
1 procedural blank,
1 laboratory blank
(extraction time points:
4 and 7 hours; 1, 2, 3,
7, and 10 days after
spike)
* Unsealed concrete and ceiling tile test coupons were placed on top of polytetrafluoroethylene (PTFE) disks,
t Breakthrough controls were placed on top of M8 paper, which was intended to detect the presence of liquid VX
that might seep through these coupons.
Note: all coupons (as well as PTFE disks and M8 paper) were placed in trays lined with an absorbent wipe, which
helped pick up the coupons for extraction.
• For both unsealed concrete and ceiling tile, three breakthrough control coupons were
spiked with 2 |iL of VX and placed on top of M8 Chemical Detection Paper (M8 paper)
(Luxfer Magtech, Cincinnati, OH, USA). The M8 paper was cut to the coupon
dimensions and was used with the intent to detect liquid VX that might seep through the
coupons. At the end of each time point, the M8 paper was checked for a color change
indicating that VX had migrated through the coupon; no other chemical analysis was
used for the breakthrough control coupons.
• Two of the five unsealed concrete and ceiling tile test coupons were placed on top of
PTFE disks (cut to the coupon dimensions). The PTFE disks were used to capture any
VX that might migrate through the coupons. If the breakthrough controls/M8 paper
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indicated that VX had migrated through the material at a given time, the test coupons and
PTFE disks would have been extracted and analyzed separately for VX. However, in all
cases the breakthrough control coupons/M8 paper did not indicate that VX migrated
through the material, so the test coupons and PTFE disks were extracted together.
• Five coupons of each material type were extracted at 30 minutes (min) after spiking plus
seven additional time points (weathering periods) as shown in Table 1. The weathering
periods differed for each environmental condition given the anticipated differences in the
persistence of VX. The weathering periods were chosen to maximize information on the
duration that VX persists under the various environmental conditions rather than
generating a more uniform sampling pattern over time.
• In addition to the five test coupons, one procedural blank coupon (a coupon inside the test
chamber that was not spiked with VX) of each material type and one laboratory blank
coupon (a coupon kept outside the agent hood and test chamber that was not spiked with
VX) of each material type were extracted and analyzed along with the test coupons at
each time point.
2.3 Test Chamber
A custom-fabricated acrylic test chamber was used for testing that enabled monitoring,
recording, and control of temperature, RH, and chamber air exchange. The test chamber was held
within a chemical fume hood for secondary containment.
Temperature within the test chamber was adjusted with a radiator/heat exchanger (Part #
3525K25, McMaster-Carr, Aurora, OH) installed at the top of the chamber. The heat exchanger
was fed by a refrigerated/heated bath circulator filled with propylene glycol heat transfer fluid
(-28 °C to 150 °C operating range, ±0.1 °C temperature stability, 500 Watt cooling capacity, 1
kilowatt heating capacity). Humidity was added to the chamber air using a Nafion®
humidification tube (Model #FC100-80, Perma Pure LLC, Toms River, NJ). House air was fed
through the Nafion® tube to achieve the desired RH and then supplied to the chamber. The
supplied house air was directed through a series of particulate filters (rated as low as 0.01
micrometers [|im]) and desiccant dryers to clean and dry the air prior to delivery to the
laboratory. A redundant carbon filter and moisture trap were installed at the test chamber supply
air inlet (upstream of the Nafion® tube) to further clean and dry the air. Chamber supply air
exchange was controlled using a calibrated mass flow controller to achieve one air exchange per
hour.
Process controllers integrated into the heat exchanger and Nafion® tube circulator baths were
used to control temperature and RH. Test chamber temperature and RH was monitored and
recorded using a calibrated Vaisala temperature/RH probe (HMT338, Vaisala Oyj, Helsinki,
Finland). In addition, shelf-specific temperature and RH monitoring was conducted with HOBO
data loggers (UX100-003, Onset Computer Corporation, Bourne, MA). A double-door-
controlled access port (airlock) in the test chamber allowed for the addition or removal of
coupons and supplies with minimal disturbance to the controlled environmental conditions
within. Five- cm thick closed-cell foam insulation was also used to prevent chamber heat
loss/gain. To minimize the exposure of the coupons to ultraviolet light, lights in the fume hood
6
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and laboratory were turned off when not needed. Light-emitting diode (LED) bulbs emitting little
to no ultraviolet light were used inside the test chamber, and black Kraft paper (Part # 883458,
Staples, Columbus, OH) was used to block light at the hood face when no work was being
performed. Glove ports allowed the chamber to remain sealed while operators manipulated
coupons and supplies within the chamber. Circulation fans mounted inside the chamber just
above the heat exchanger helped to ensure uniformity of the environmental parameters. Fans
were oriented so that air flow was not directed at the coupons.
2.4 Test Materials
The natural attenuation investigation was conducted using the following six types of material
coupons: unsealed concrete, plywood, rubber escalator handrail, HDPE plastic, ceiling tile, and
silanized glass (a nonporous reference material). Table 2 describes the materials and preparation
approaches used. Coupons were cut to uniform length and width (4.0 cm x 2.5 cm) from larger
pieces of material. Edges and damaged areas were avoided in cutting test coupons. Glass
coupons were silanized following a modification of the method of Labit et al. (2008).
Table 2. Description of Materials Used for the Natural Attenuation Investigation
Material
Description
Supplier -
Location
Coupon
Length (cm)
x Width (cm)
Coupon
Preparation
Unsealed
concrete
Type II Portland Cement was obtained from a
ready-mix supplier. The cement, which met
uniform building code specifications for structural
walls, was delivered (to the Idaho National
Laboratory [INL]) in April 2004. The cement was
originally poured into 3-foot x 3-foot x 2-inch
plywood molds and then troweled to form a
finished surface. After curing, the cement was
removed from the molds and cut into 6-inch x 6-
inch blocks, some of which have been used by
U.S. Department of Homeland Security, Battelle,
and INL.
Unspecified
supplier -
Idaho Falls, ID
4.0 x 2.5
(cut to 0.5 cm
thickness)
Cleaned with
dry air to
remove dust
Plywood
Pine subfloor plywood 23/32 CAT PS 1-09
(common: 23/32-inch x 4-foot x 8-foot; actual:
0.703-inch x 47.5-inch x 95.875-inch) (Item #:
12249)
Lowe's -
Hilliard, OH
4.0 x 2.5
(cut to 0.75 cm
thickness)
Cleaned with
dry air to
remove dust
Rubber
escalator
handrail
Standard Otis escalator handrail (20-foot section)
Porta-Flex
Manufacturing -
Ajax, ON
4.0 x 2.5
Cleaned with
dry air to
remove dust
HDPE
plastic
MacCourt drywall mud pan (Item #: 19251,
Model #: AT2606)
Lowe's -
Hilliard, OH
4.0 x 2.5
Cleaned with
dry air to
remove dust
Ceiling
tile
Armstrong® random textured contractor 10-pack
white textured 15/16-inch drop acoustic panel
ceiling tiles (common: 48-inch x 24-inch; actual:
47.719-inch x 23.719-inch) (Item #: 55612, Model
#: 933)
Lowe's -
Hilliard, OH
4.0 x 2.5
Cleaned with
dry air to
remove dust
7
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Material
Description
Supplier -
Location
Coupon
Length (cm)
x Width (cm)
Coupon
Preparation
Silanized
glass*
Window glass (initially uncoated)
Brooks Brothers
-West Jefferson,
OH
4.0 x 2.5
Silanized*
* Silanized glass was used as a nonporous reference material. The process used to silanized the glass is according to
Labit et al. (2008).
2.5 Chemical Agent and Spiking Coupons
All quantities of neat VX used for this project were synthesized at the Battelle HMRC in
December 2015, under the Chemical Weapons Convention program guidelines, with
accountability through the U.S. Army Edgewood Chemical Biological Center. All neat VX
originated from the same synthesis lot and was sealed in multiple glass ampoules (i.e., one
ampoule was intended to be used per test, with the sealed volume based on the anticipated need
for a particular test). The ampoules used are listed below along with VX purity (if measured).
VX purity was measured four times during this testing by GC/flame ionization detector (FID).
The VX (ampoules) used and associated purity during this project were:
• Ampoule C063-1: VX used for the extraction recovery method demonstrations. VX
purity was 95.2% as measured on February 8, 2016.
• Ampoule C063-2: VX used for spiking most coupons associated with Environmental
Condition 1. VX from ampoule C063-2 was depleted after spiking all coupons and the
first four spike controls. VX purity was not measured from this ampoule. For the
calculation of the percent recovery of VX for the first spike controls of Environmental
Condition 1, the VX purity of ampoule C063-1 was used.
• Ampoule C063-7: VX used to complete the spiking of the Environmental Condition 1.
This VX was used for the remaining spike controls and purity testing. VX purity was
95.7% as measured on March 14, 2016. For the calculation of the percent recovery of VX
for the spike controls (see Section 2.8, equation 4) of Environmental Condition 1, the VX
purity of ampoule C063-1 was used. Ampoules C063-1 and C063-2 were sealed until
being used for this testing, while ampoule C063-7 had previously been unsealed and then
recapped before being used in this testing.
• Ampoule C063-3: VX used for spiking the coupons associated with Environmental
Condition 2. VX purity was 95.6% as measured on May 2, 2016.
• Ampoule C063-4: VX used for spiking the coupons associated with Environmental
Condition 3. VX purity was 95.7% as measured on July 5, 2016.
The coupons were visually inspected prior to spiking with the neat VX; coupons with surface
anomalies such as visible scratches or divots were not used. The VX was dispensed using a
Hamilton repeating dispenser (#PB600-1, Hamilton, Reno, NV) and 100 |iL Hamilton syringe
(#81085, Hamilton, Reno, NV). All test coupons were spiked with a single 2 |iL droplet of VX.
The coupons were open to the atmosphere within the test chamber. After weathering in the
8
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environmental conditions for a given experiment and specified time, a batch of coupons was
transferred from the test chamber into solvent for extraction. This process was repeated for each
time point in the test matrix.
2.6 Extraction of VX from Coupons
All test and blank coupons in the test matrix were extracted by placing each coupon into a
separate 60-milliliter (mL) glass bottle (05-719-257, Fisher Scientific, Pittsburgh, PA) containing
25 mL of applicable extraction solvent: hexane (H306SK-4, Fisher Scientific, Pittsburgh, PA)
with the N,N'-diisopropylcarbodiimide (DIC) (AC 11521-5000, Fisher Scientific, Pittsburgh, PA)
VX stabilizer or acetone (A929-4, Fisher Scientific, Pittsburgh, PA) with DIC, based on the
outcome of method demonstration work described in Section 2.7. The use of the DIC is intended
to stabilize VX in dilute concentrations by inhibiting VX degradation (EPA, 2013). The VX
stabilizer DIC was added to the extraction solvent at 1% by volume. The stabilizer also helped to
improve the sensitivity of the GC/MS analysis of VX samples. The hexane and acetone
extraction solvents used during this study were of Optima™ grade to ensure the highest purity
possible (> 99%). The hexane used was > 95% «-hexane and > 99% for all hexanes). Internal
standard (IS), naphthalene-dx (AC 17496-0010, Fisher Scientific, Pittsburgh, PA), was added to
the extraction solvent stocks at a concentration of 2.5 micrograms (|ig)/mL. The 4.0 cm x 2.5 cm
coupons fit lying flat within the inside diameter of the bottles, and 25 mL of liquid reached a
height of approximately 1.3 cm (higher when liquid was displaced by coupons). This bottle and
volume of extraction solvent were generally sufficient to submerge the coupons. For the coupon
that floated (i.e., ceiling tile), the coupons were extracted with the VX-spiked side facing down.
In addition, the PTFE disks associated with the unsealed concrete and ceiling tile were also
extracted along with the test coupons (in the same bottle).
Following addition of coupons, the bottles were swirled by hand for approximately 5 to 10
seconds and placed into a sonicator (Branson Model 5510, Danbury, CT). Extraction bottles
were sonicated at 40 kilohertz (kHz) to 60 kHz for 10 min. This coupon extraction approach was
based on high recoveries for the extraction of VX from similar materials (EPA, 2011). Within 30
min of completing this process, approximately 1 mL from each extraction bottle was transferred
to individual GC vials (vial P/N 21140, cap P/N 24670, Fisher Scientific [Restek Corporation],
Hanover Park, IL) and sealed. Samples not analyzed the same day as extraction were stored at -
20 °C or lower.
2.7 Extraction Recovery Method Demonstration
This method demonstration study evaluated the ability to recover VX from unsealed concrete,
plywood, rubber escalator handrail, HDPE plastic, ceiling tile, and silanized glass coupons 24
hours after the coupons were spiked with VX and held under ambient laboratory conditions.
When considering method demonstration for extraction from hard, nonporous surfaces, a shorter
time of up to 60 min is typically used. The 24 hours contact time in this study allows for
permeation to occur on a longer time scale prior to extraction. The coupons were spiked with a
single 2-|iL droplet of VX as described in Section 2.5. During the extraction recovery testing, the
coupons were placed into 60 millimeter (mm) x 15 mm Petri dishes (AS4052, Fisher Scientific,
9
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Waltham, MA) or 4.8 cm x 4.8 cm x 2.9 cm acrylic boxes (10172618, Michaels, Irving, TX), see
Figure 1.
The lids on the dishes/boxes were loosely placed on top to prevent accidental contact with VX
during the weathering time, while allowing for natural evaporation/attenuation to occur under
ambient environmental conditions. The extraction approach described in Section 2.6 was
employed with four different extraction solvents:
• hexane with IS
• hexane with IS and DIC
• acetone with IS and DIC
• dichloromethane (D151-1, Fisher Scientific, Pittsburgh, PA): acetone (1:1 ratio by
volume) with IS and DIC.
Figure 1. Photograph of coupons associated with the extraction recovery method
demonstration showing use of round Petri dishes and square acrylic boxes.
The extraction recovery method demonstration was evaluated as follows:
• For each extraction solvent and material combination evaluated, three VX-spiked test
coupons, one procedural blank (an unspiked coupon handled similarly to the test
coupons), and one laboratory blank (an unspiked coupon never placed inside the agent
hood) were extracted. In addition, three spike controls (a spike of equal amount of VX
directly applied into the extraction solvent) were used.
10
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• Coupons were spiked as described in Section 2.5 and extracted as described in Section
2.6. Coupon extractions took place 24 hours after the test coupons were spiked. The
analytical methods followed those documented in Section 2.8.
• For the unsealed concrete and ceiling tile, PTFE disks were placed underneath these
coupons (to capture any VX that might migrate through the materials). The PTFE disks
and coupons were extracted and analyzed together for VX.
• The acceptable recovery of VX targeted for each of the materials was 70% to 120% of
the mean spike control recovery with less than a 30% coefficient of variation (CV)
between triplicate samples.
2.8 Analytical Methods
2.8.1 Analysis for VX
The sample extracts were analyzed to quantify the amount of VX remaining on each coupon
using GC/MS (6890 gas chromatograph and 5973 mass-selective detector, Agilent Technologies,
Santa Clara, CA) operated in the full-scan mode for compounds ranging from 40 to 500 atomic
mass units. VX was detected with ions 114, 72, 127, and 79. The GC/MS parameters are
documented in Table 3. Example chromatograms, including one high-curve analysis and one
low-curve analysis (refer to Section 4.2), are provided in Appendix A. See Section 4.2 for
equipment calibration information as well as GC performance parameters and acceptance criteria
that ensure the accuracy and reproducibility of the integration of the ion peaks. The integration of
the target ion and qualifier ion peaks was conducted primarily by the GC/MS software, but every
single peak in every sample and standard was also reviewed by the GC/MS analyst.
The lowest standard used to establish the calibration curve (quantitation limit) was above, but
near, the GC/MS instrument detection limit. Samples with results below the lower calibration
level (i.e., 0.10 |ig/mL) were reported as less than the quantitation limit ("non-detects").
11
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Table 3. Gas Chromatography/Mass Spectrometry Conditions
Parameter
Description
Instrument
Hewlett Packard Model HP 6890 Gas Chromatograph equipped with HP
5973A Mass Selective Detector and Model 7683 Automatic Sampler
Column
30 meters x 0.25 mL inside diameter Rtx-5 (cross-linked methyl-silicone),
fused silica capillary column, 0.25 |_im film thickness (Restek Catalog Number
05223)
Carrier gas flow rate
1.2 mL/min helium (constant flow)
Column temperature
40 °C initial temperature, hold 1 min, 30 °C/min to 280 °C, hold 0 min
Injection volume/type
1 |_iL splitless injection (4 mm inside diameter single gooseneck quartz insert)
with 0.5 min purge activation time. Split vent flow rate at 80 mL/min
Injection temperature
250 °C
Transfer line temperature
280 °C
MS quad temperature
150 °C
MS source temperature
230 °C
Ionization mode
Electron ionization
Solvent delay
3 min
The VX concentration in coupon extract samples and spike control samples was calculated by
the GC/MS instrument software and is provided in units of |ig/mL. The GC/MS analysis result
for each extract sample was fitted to the calibration curve generated for the specific GC used to
analyze the sample, and VX concentration was determined from the ratio of the VX peak area
response to that of the IS peak area response. Use of an IS compensated for potential variability
in sample injection volumes as well as decreasing or increasing instrument sensitivity. During
the effort, VX exhibited a quadratic response over the concentration range analyzed, and thus the
ratio of VX area response to the IS area response (y-axis) was plotted versus the ratio of VX
concentration to IS concentration (x-axis). The quadratic VX calibration curve that was fitted to
the analysis data took the following form:
(As / A is) = [a x (Cs / Cis)2] + [b x (Cs / Cis)] + c (1)
where:
As = area response of the target analyte
Ais = area response of the internal standard
Cs = concentration of the target analyte
Cis = concentration of the internal standard
a, b, c = coefficients of quadratic curve fit
VX concentrations in the coupon extracts were calculated by GC/MS instrument software and
are provided in units of ng/mL. These GC concentration results (|ig/mL) were converted to total
mass recovered by multiplying by the extract volume:
12
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Mm - Cs x Ev (2)
where:
Mm = calculated mass of VX recovered from an individual
replicate (|ig)
Cs = GC concentration (|ig/mL) from an individual replicate, see Equation 1
Ev = extraction solvent volume (mL).
The percent recovery of VX recovered from an individual replicate relative to the mean mass
measured in spike controls was calculated as follows:
%R = Mm / Msc x 100% (3)
where:
%R = percent recovery for an individual replicate
Mm = calculated mass of VX recovered from an individual replicate (|ig)
Msc = mean calculated mass of VX recovered from spike controls (|ig).
A separate %R calculation was made for recovery of VX from each replicate coupon. The mean
%R was based on the mean of the %R for all applicable replicates.
The percent recovery of VX from spike controls (versus theoretical) was calculated as follows:
%Rsc = [Mm / (D / CFi x Sv x CF2 x P)] x 100% (4)
where:
%Rsc = percent recovery for an individual spike control replicate (versus theoretical)
Mm = calculated mass of VX recovered from an individual replicate (|ig)
D = density of VX (grams/cubic centimeter)
CFi = conversion factor 1 (1000 |iL/ cubic centimeter)
Sv = VX spike volume (|iL)
CF2 = conversion factor 2 (1,000,000 gram/|ig)
P = VX purity (as a fraction)
A separate %Rsc calculation was made for recovery of VX from each spike control replicate.
The mean %R was based on the mean of the %Rsc for all applicable replicates.
2.8.2 Analysis for VX Hydrolysis Product
The sample extracts were also analyzed to provide a semi-quantitative estimate of the amount of
the VX hydrolysis product ethyl methylphosphonic acid (EMPA). The detection of other VX
degradation products including highly toxic EA-2192 was not attempted because such an
analysis would require the use of liquid chromatography/MS, which was beyond the scope of
this study.
In preliminary testing, 10 |ig/mL of EMPA was not directly detected in the extraction solvents
hexane or acetone via GC/MS as described in Section 2.8.1 for the analysis of VX. The solvents
13
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might have caused a reaction with the EMPA, or EMPA might have degraded in the hot inlet of
the GC; however, two degradation products of EMPA, diethyl methylphosphonate [Dl] and
diethyl dimethylpyrophosphonate [D2] were detected. Dl and D2 are known degradation
products of EMPA and sometimes impurities associated with VX (Munro et al., 1999). The
combination of detecting degradation products of EMPA, use of a single EMPA standard, and
lack of information on how effective the extraction process is for EMPA from a coupon makes
the EMPA analysis semi-quantitative.
The subsequent analysis of the EMPA degradation products was conducted using GC/MS (6890
gas chromatograph and 5973 mass selective detector, Agilent Technologies, Santa Clara, CA)
operated in the full scan mode for compounds ranging from 40 to 500 atomic mass units, as
described in Section 2.8.1. Dl was detected with ions 79, 97, and 125, and D2 was detected with
ions 203, 143, and 175.
An EMPA standard at 81 |ig/mL, which is equivalent to the VX concentration in the spike
controls assuming 100% VX purity, was included in the analytical run (along with the VX
calibration curve and the VX continuing calibration verification [CCV] standards described in
Section 4.2). An intermediate EMPA standard at 3 milligrams/mL was prepared first by addition
of neat EMPA (98% purity, 386561-1G, Sigma-Aldrich, St. Louis, MO) to the hexane and
acetone extraction solvents containing IS and DIC. The intermediate was then diluted to the 81
|ig/mL concentration standard included in the analytical runs. The EMPA standard served as a
single "calibration point" that was used to compare the EMPA-associated peaks of the test
samples.
For the initial analyses associated with Environmental Condition 1, an 81 |ag/m L EMPA
standard was included with the high VX calibration curve and a 10 |ag/m L EMPA standard was
included with the low VX calibration curve. There was concern that using the 81 |ig/mL EMPA
standard with the low VX calibration curve might cause saturation of the GC/MS detector
possibly resulting in unusable data. However, chromatograms with responses exceeding as high
as 700%) of the low EMPA standard response were found to be of no danger to the GC/MS
detector (i.e., no visual saturation in the chromatogram for EMPA byproducts) that would
influence the VX response. Hence, it was acceptable to use the 81 |ig/mL EMPA standard with
the low VX calibration curve.
The 81 |ig/mL EMPA standard was then used with the low and high VX calibration curves for
all of the 28-day samples for Environmental Condition 1 and all the remaining tests. Using the
same EMPA standard concentration with both the low and high VX calibration curves improved
the comparability of the results as the reported Dl and D2 peak areas were related to the single
EMPA standard. The concentrations recovered from the standard provided estimates of the
maximum response from each EMPA degradant if all the VX on a particular coupon were to
degrade into EMPA. Peak areas were reported for the two EMPA degradants in the standard as
well as in all the samples for each analytical run.
14
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2.9 Analysis of Variance (ANO VA) to Test Hypotheses
SAS/STAT® software (SAS Institute Inc., Gary NC) was used to fit an ANOVA model to the
study data to test the three hypotheses noted in Section 2.1. The ANOVA model took the
following form:
ln('Yijkn) — M ai + (
-------
addition, any residual mass values reported as below the lower calibration limit of 2.5 |ig were
included in the analysis as 2.5 |ig.
How the results of the ANOVA model fitting were used in performing the three sets of statistical
hypothesis tests to address study objectives is detailed below. Recall that in statistical hypothesis
testing, null and alternative hypotheses are specified, and the null hypothesis is assumed to hold
unless the observed data (as applied to the statistical test procedure) are sufficient to support
rejecting the null hypothesis for the alternative. All statistical tests were performed at a 0.05
significance level unless otherwise noted, meaning that the likelihood of incorrectly rejecting the
null hypothesis for the alternative based on the observed data is no more than 5%.
Test #1:
• Null hypothesis'. No decline occurs in mean recovered VX over time.
• Alternative hypothesis: Mean recovered VX declines over time.
Test #1 addressed whether the mean slope (A + /? + f) associated with the time factor (i.e., the
mean VX loss rate) was significantly less than 0 (i.e., an overall exponential decline occurs in the
mass measurement with increasing time), where /? and f represent the mean of the incremental
amounts added to the slope that are specific to the environmental condition and material type,
respectively. In addition, statistical tests of whether the environmental condition-specific slope
(A + y + Pi) or the material-specific slope (A + /? + Yj) is significantly less than 0 were
performed, in order to determine whether observing a significant rate of decline was dependent
on either the environmental condition or material type.
Test #2:
• Null hypothesis: The mean rate of VX loss does not change among different
environmental conditions (temperatures).
• Alternative hypothesis: The mean rate of VX loss differs among environmental condition
(temperatures).
Because the three attenuations were distinguished by temperature, this test considered whether
the attenuation effect was statistically significant on average across the time points.
Test #2 addressed whether the attenuation-specific slopes (A + y + /?;) differed significantly from
each other at the 0.05 level, indicating that the rate of decline in residual mass measurement of
VX over time differed among the three environmental conditions. If so, then pairwise differences
in these slopes (i.e., differences among the Pi values) were statistically compared at an overall
0.05 level (i.e., each test performed at a 0.05/3=0.0167 level) to determine which of the three
pairs of environmental conditions differed significantly in their rates of decline.
In addition, statistical tests were performed to determine whether the mean VX residual mass
value differed among the three environmental conditions. First, the significance of the interaction
term (aM)ij was tested at the 0.05 level to determine whether the significance of the mean
attenuation effect was dependent on the material type.
16
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1. If this interaction term were significant, then statistical comparisons between pairs of
environmental conditions were done by material type, with the overall significance level
among all three pairs of the three environmental conditions being no higher than 0.05
within each material type (i.e., each test performed at a 0.05/3=0.0167 level). No further
tests were performed.
2. If the interaction term was not significant, then a test for significance of the main
attenuation rate term a., was performed at a 0.05 level.
a. If this test was significant, then at least one of the attenuation rates
-------
b. If this test was not significant, then on average across time points, the six material
types did not differ significantly overall or within any environmental condition.
18
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3.0 Test Results
3.1 Extraction Recovery Method Demonstration Results
As discussed in Section 2.7, extraction recovery was determined 24 hours after spiking coupons
of unsealed concrete, plywood, rubber escalator handrail, HDPE plastic, ceiling tile, and
silanized glass with 2 |iL of VX. Four extraction solvents were tested: hexane (referred to as
hexane without DIC), hexane with DIC (referred to as simply hexane), acetone with DIC
(referred to as simply acetone), and dichloromethane: acetone (1:1) with DIC (referred to as
dichloromethane:acetone). All extraction solvents contained the IS. The results of the recovery
efficiency test are summarized in Figure 2 and Table 4. During this testing, the temperature
varied from 18.1 °C to 21.3 °C, and the RH ranged from <15% to 34.8%. The HOBO data logger
(Onset Computer Corporation, Bourne, MA) used to monitor temperature and RH had a
minimum RH reporting level of 15%. The mean spike control recoveries ranged from 82% to
102%. The spike control recoveries were calculated based on the amount and purity of VX
spiked. As noted in Section 2.5, the purity of VX was 95.2% for all method demonstration tests.
Per Section 2.7, acceptable recoveries of VX were defined as having mean recoveries relative to
the spike control of 70% to 120% with less than a 30% CV between samples. None of the
extraction solvents tested achieved 70% VX recovery from unsealed concrete. Mean percent VX
recoveries ranged from 12% to 20%, and the CV ranged from 37% to 63%. Low VX recoveries
were also obtained from epoxy-sealed concrete in a companion study (EPA, 2016). The poor
recoveries might be attributed to strong adsorption and/or degradation of the VX within the
concrete (Groenewold et al., 2002). In fact, Groenewold et al. (2002) demonstrated the near
complete VX degradation when VX was exposed to crushed concrete. Nevertheless, detectable
VX was recovered with all four extraction solvents (ranging from 230 |ig to 388 |ig) 24 hours
after spiking.
0 o
u u
¦K oi
cr -x
x "5.
> «
N? O
O -M
= s
01 ^
110%
100%
Unsealed Plywood Escalator HDPE Ceiling Silaniied
Concrete Handrail Plastic Tile Glass
Material
I Hexane without DIC
IHexane
Acetone
Dichloromethane: Acetone (1:1)
Figure 2. VX recoveries following coupon extraction in various solvents (error bars equal
plus one standard deviation).
19
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Table 4. VX Recoveries from Materials Extracted Using Different Solvents (all with IS)
Measure of
Extraction Solvent
Material
VX Recovery
Hexane
Hexane
Acetone
Dichloromethane:
without DIC
Acetone (1:1)
Spike Control
Mean (|_ig)
1723
1577
1929
1963
SD (jig)
128
34
81
59
% Recovery*
90
82
100
102
SD (%)
6.7
1.8
4.2
3.1
CV (%)
7.4
2.2
4.2
3.0
Unsealed concrete
Mean (|_ig)
285
263
230
388
SD (fj-g)
108
97
89
246
% Recovery*
17
17
12
20
SD (%)
6.3
6.1
4.6
13
CV (%)
38
37
39
63
Plywood
Mean (ng)
1206
1016
1405
1190
SD fog)
27
168
9.8
338
% Recovery*
70
64
73
61
SD (%)
1.6
11
0.51
17
CV (%)
2.2
17
0.70
28
Rubber escalator
Mean (ng)
993
1199
960
1390
handrail
SD fog)
93
69
201
68
% Recovery*
58
76
50
71
SD (%)
5.4
4.4
10
3.5
CV (%)
9.4
5.8
21
4.9
HDPE plastic
Mean (ng)
1620
1582
1738
1751
SD fog)
63
56
187
34
% Recovery*
94
100
90
89
SD (%)
3.6
3.6
9.7
1.7
CV (%)
3.9
3.6
11
1.9
Ceiling tile
Mean (ng)
1347
1370
1660
1570
SD (fJ-g)
100
172
97
71
% Recovery*
78
87
86
80
SD (%)
5.8
11
5.0
3.6
CV (%)
7.4
13
5.9
4.5
Silanized glass
Mean (ng)
1577
1639
1793
1654
SD (jig)
3.3
36
216
43
% Recovery*
92
104
93
84
SD (%)
0.19
2.3
11
2.2
CV (%)
0.21
2.2
12
2.6
SD = standard deviation of (here) the % Recovery; three replicate coupons were extracted per material and
extraction solvent. All of the results were quantifiable; there were no non-detect results.
CV = coefficient of variation.
* % recovery (mean) for spike controls is relative to the theoretical recovery, and % recovery (mean) for the
material samples is relative to the associated spike control.
Note: all associated laboratory and procedural blanks were non-detect for VX (<2.5 |ig).
For plywood, acceptable VX recoveries relative to the spike control were obtained when using
hexane without DIC (70% mean recovery and a CV of 2.2%) and acetone (73% mean recovery
20
-------
and a CV of 0.7%). Lower mean VX recoveries from plywood occurred when using hexane
(64%) and dichloromethane:acetone (61%).
In contrast to the results obtained with plywood, the VX recoveries from rubber escalator
handrail were acceptable when using hexane or dichloromethane:acetone but not when using
hexane without DIC or acetone. When using hexane, the mean VX recovery from the rubber
escalator handrail was 76% with a CV of 5.8%. For dichloromethane:acetone, the mean VX
recovery from the rubber escalator handrail was 71% with a CV of 4.9%. Lower mean VX
recoveries from the rubber escalator handrail occurred when using hexane (58%) and acetone
(50%).
For HDPE plastic, ceiling tile, and silanized glass, all mean VX recoveries relative to the spike
controls were >78% and all CV were <13%. As such, each of the extraction solvents was found
to be acceptable for these materials. Silanized glass was used as a nonporous reference material
to account for evaporative losses. The mean VX recoveries relative to the spike control from
silanized glass ranged from 92% to 104% for all extraction solvents, except
dichloromethane:acetone, which had a mean VX recovery of 84%. Considering the VX
recoveries from silanized glass, some of the applied VX might be unrecoverable due to the use of
an incomplete extraction process or losses associated with VX evaporation or degradation.
Based on the extraction recovery method demonstration results, hexane (with DIC) was selected
as the extraction solvent for unsealed concrete, rubber escalator handrail, HDPE plastic, ceiling
tile, and silanized glass. Acetone with DIC was selected as the extraction solvent for plywood.
3.2 Natural Attenuation Results
3.2.1 Environmental Condition 1
The first environmental condition evaluated was 25 ± 3 °C, 40 ± 5% RH, with one chamber
volume of air exchanged per hour. The actual temperature as measured by the Vaisala probe and
the shelf-specific HOBO data loggers was consistently maintained within 25 ± 1 °C for all test
durations. The actual RH measurements taken during this test are presented in Appendix B. In a
few instances, the target RH was not maintained, but the magnitude and duration of these
instances was relatively minor. The Vaisala measurement provided the overall conditions in the
test chamber. The HOBO measurement on individual shelves was used to confirm that
substantial differences in microenvironments did not exist between shelves.
After each weathering period (prior to extraction), the physical appearance of the coupons was
noted (Table 5). Unsealed concrete and plywood were described at 30 min as having a "soak"
spot, either dark or faint in color, where the VX was applied. Subsequent observations of the
unsealed concrete and plywood throughout the entire exposure included faint and dark spots, but
often there were no visible changes to the coupons, especially as the exposure times increased.
The rubber escalator handrail initially had a "pancake" appearance (Figure 3) where the VX was
applied; this area became a blister after 1 day of exposure. The HDPE plastic samples had the
"pancake" appearance during the entire exposure time; at 28 days, the HDPE plastic was also
described as having a hazy appearance. Dark soak spots were initially observed on some of the
21
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ceiling tile coupons, but at the seven-hour extraction time and after, there was no VX visible. In
most cases, the VX applied to silanized glass coupons had either a "pancake" appearance (Figure
3) or looked to have spread across the coupon (Figure 4). After the seven-day and longer
durations, a variety of observations were noted, including: wet, hazy, or no VX visible.
None of the breakthrough control coupons (i.e., spiked unsealed concrete and ceiling tile
coupons placed on M8 paper) indicated the presence of VX via a color change (i.e., the VX did
not migrate through these especially porous coupons). The unsealed concrete and ceiling tile test
coupons were therefore extracted along with the PTFE disks on which they were placed.
Table 5. Observations Associated with Environmental Condition 1* across Replicates
Material
30 min
7 hours
1 day
Weathering Period
2 days 4 days
7 days
14 days
28 days
Unsealed
concrete
Soak;
dark spot;
faint spot
Faint spot;
no VX
visible
Dark Spot;
no VX
visible
No VX
visible
No VX
visible
Faint Spot;
no VX
visible
No VX
visible
No VX
visible
Plywood
Soak;
dark spot
Dark spot;
no VX
visible
Dark spot;
faint spot
Faint spot;
no VX
visible
No VX
visible
No VX
visible
No VX
visible
No VX
visible
Rubber
escalator
handrail
Pancake
Pancake
Blister;
white
smear
Blister
Blister
Blister
Blister
Blister
HDPE
plastic
Pancake
Pancake
Pancake
Pancake
Pancake
Pancake
Pancake
Pancake;
haze
Ceiling
tile
Soak;
dark spot;
no VX
visible
No VX
visible
No VX
visible
No VX
visible
No VX
visible
No VX
visible
No VX
visible
No VX
visible
Silanized
glass
Pancake;
spread
Pancake;
spread
Pancake;
spread
Pancake;
spread
Pancake;
spread;
hazy
Wet;
hazy;
no VX
visible
Wet;
hazy;
no VX
visible
Hazy
* Differing observations (e.g., dark spot versus no VX visible) occurred on different replicate coupons.
Observations were only recorded for each coupon replicate prior to extraction; repeated observations over time were
not documented for the same replicate coupon.
22
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Figure 3. Photograph of silanized glass coupon with VX having a "pancake" appearance.
Figure 4. Photograph of silanized glass coupon with VX having a "spread" appearance.
The mean spike control recoveries for VX during testing at Environmental Condition 1 were
2199 ug from the hexane spike controls and 2301 from the acetone spike controls. Hexane was
23
-------
used as the extraction solvent for unsealed concrete, rubber escalator handrail, HDPE plastic,
ceiling tile, and silanized glass. Acetone was used as the extraction solvent for plywood.
The amount of VX recovered over time is presented in Figure 5 and Table 6. After a 30-min
weathering period, the mean VX recoveries were >1537 |ig for all materials, except unsealed
concrete, which had a mean VX recovery of 684 |ig. The VX recoveries rather steadily decreased
from unsealed concrete. The mean VX recovery from plywood was 871 |ig after two days but
rapidly decreased to 134 |ig after four days. Similarly, rapid decreases in VX recoveries occurred
from HPDE plastic, ceiling tile, and silanized glass which had mean recoveries >1080 |ig after
four days and mean VX recoveries <472 |ig from these materials after seven days. The overall
decrease in VX was slowest from the rubber escalator handrail, which had mean VX recoveries
of 703 |ig after seven days, 423 |ig after 14 days, and 187 |ig after 28 days. VX was recovered
from at least some of the replicates of all materials tested after 14 days; the highest mean VX
recoveries were from rubber escalator handrail (423 |ig), ceiling tile (152 |ig), and HDPE plastic
(66 |ig). The remaining materials had mean VX recoveries <10 |ig after 14 days. After 28 days,
VX was detected from at least one of the five replicate coupons for all materials except plywood
and silanized glass. Mean VX recoveries remained above 10 jj.g after 28 days for the rubber
escalator handrail (187 |ig) and ceiling tile (33 |ig).
2400
2200 T ¦ Unsealed concrete
2000 T T I T It It ¦ Plywood
-r; I I' I I I ¦ _ ¦ Rubber escalator handrail
¥ 1800 I I T
—- III I I ^ ¦ HDPE plastic
"g 1600 I I | I ¦ TtH IT I Ceiling tile
> 1400 II I ¦ ¦ II ¦ 1 Silanized glass
"io° II II II il b
iooo t| I II —rl
1J1 ]| J I .
30 minutes 7 hours 1 day 2 days 4 days 7 days 14 days 28 days
Extraction Time (Weathering Period)
Figure 5. VX recovery at Environmental Condition 1 (error bars equal plus one standard
deviation). Initial VX amount is 2200 jig.
24
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Table 6. VX Recovery at Environmental Condition 1
Material
Measure of
VX Recovery
30 min
I
7 hours
Extraction Time (Weathering Period)
1 day 2 days 4 days 7 days 14 days
28 days
Unsealed
concrete*
Mean (jig)
684*
381
275
198
77
53
6.9
2.6
SD (jig)
377
64
125
27
32
24
6.6
0.31
CV (%)
55
17
45
14
42
46
96
12
FOD
5/5
5/5
5/5
5/5
5/5
5/5
3/5
1/5
PB (jig)
<2.5
<2.5
14
17
13
4.8
<2.5
<2.5
Plywood1^
Mean (jig)
1935
1776
1436
871
134
47
7.5
<2.5
SD (jig)
123
152
192
233
40
10
1.2
0
CV (%)
6.4
8.6
13
27
30
21
16
0
FOD
5/5
5/5
5/5
5/5
5/5
5/5
5/5
0/5
PB (jig)
<2.5
<2.5
<2.5
12
29
25
18
<2.5
Rubber
escalator
handrail*
Mean (jig)
1959
1975
1227
731
908
703
423
187
SD (jig)
114
189
404
558
104
216
116
71
CV (%)
5.8
9.6
33
76
11
31
27
38
FOD
5/5
5/5
5/5
5/5
5/5
5/5
5/5
5/5
PB (jig)
<2.5
<2.5
11
12
26
74
31
14
HDPE
plastic*
Mean (jig)
2158
2040
2030
1905
1702
388
66
9.5
SD (jig)
73
41
68
57
141
145
16
2.4
CV (%)
3.4
2.0
3.4
3.0
8.3
37
23
26
FOD
5/5
5/5
5/5
5/5
5/5
5/5
5/5
5/5
PB (jig)
<2.5
<2.5
<2.5
<2.5
<2.5
3.2
<2.5
<2.5
Ceiling
tile*
Mean (jig)
1863
2126
1786
1504
1174
472
152
33
SD (jig)
422
212
235
167
151
61
7.0
3.6
CV (%)
23
10
13
11
13
13
4.6
11
FOD
5/5
5/5
5/5
5/5
5/5
5/5
5/5
5/5
PB (jig)
<2.5
4.0
22
21
31
36
38
7.0
Silanized
glass*
Mean (jig)
1537
1900
1611
1745
1080
122
5.2
<2.5
SD (jig)
839
117
677
196
678
196
3.7
0
CV (%)
55
6.2
42
11
63
161
71
0
FOD
5/5
5/5
5/5
5/5
5/5
3/5
3/5
0/5
PB (jig)
<2.5
<2.5
<2.5
<2.5
<2.5
<2.5
<2.5
<2.5
SD = standard deviation; five replicate coupons were extracted per material and weathering period.
CV = coefficient of variation.
FOD = frequency of detection (number of coupons above the quantitation limit/total number of coupons). For results
less than the quantitation limit. 2.5 jig was used for the calculation of summary statistics.
PB = procedural blank; all laboratory blanks were non-detect for VX (<2.5 jig). The VX detections on the PBs were
likely associated with VX volatilization and subsequent deposition/adsorption.
< = all available results were less than the quantitation limit.
* The spike control (hexane with IS and DIC) associated with these materials had a mean VX recovery of 2199 jig.
' The spike control (acetone with IS and DIC) associated with plywood had a mean VX recovery of 2301 jig.
i One unsealed concrete replicate had a comparatively low VX recovery (42 jig): this coupon may not have received
the full VX challenge as an air bubble was noted in the syringe.
As documented on Table 6, relatively low levels of VX (<74 jig or approximately 3% of amount
spiked) were recovered from the procedural blanks, which are unspiked coupons held in the test
chamber with the spiked coupons. VX recoveries were associated with the porous material
procedural blanks but not the nonporous silanized glass procedural blanks. VX was not detected
25
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from procedural blanks after 30 min, indicating that they were without VX at the start of the test.
The porous material procedural blanks appeared to adsorb VX vapor that might have volatilized
from the spiked coupons. All associated laboratory blanks (unspiked coupons never placed inside
the test chamber) were non-detect for VX.
As noted in Section 2.8.2, sample extracts were also analyzed to semi-quantitatively estimate D1
and D2. These chemicals are degradation products of EMPA, which is a hydrolysis product of
VX. This analysis was of particular interest for unsealed concrete, which was associated with
comparatively low VX recoveries. However, neither degradation product was detected in sample
extracts from the unsealed concrete. The low recovery of VX from unsealed concrete might be
attributed to the highly adsorptive properties of VX, which can make it difficult to extract and
analyze (Groenewold et al., 2002). Method development testing was not undertaken in this study
to determine the extractability of D1 or D2 applied to concrete coupons.
As shown in Table 7, the EMPA degradation product D2 was detected from plywood (after four
days), HDPE plastic (after seven days), ceiling tile (only one on replicate at seven days), and
silanized glass (after 14 days). D1 was only detected from HPDE plastic after 14 days (Table 7).
As footnoted in Table 7, in a few analytical runs, D1 was not detected in the associated EMPA
standard; in these instances, the response from D1 was simply insufficient to provide a peak. The
footnote is intended to document these instances and clarify that a semi-quantitative response for
D1 was not applicable rather than indicating a 0% response. The detection of EMPA degradation
products in these materials generally appeared to correspond with decreased recoveries of VX.
For example, the mean VX recovery from plywood decreased from 871 |ig after two days to 134
|ig after four days; D2 first appeared in the plywood samples after four days.
Table 7. EMPA Degradation Product Recovery at Environmental Condition 1*
Extraction Time (Weathering Period)
Material and
Replicate
4 days
% EMPA
7 days
% EMPA
14 days
% EMPA
28 days
% EMPA
Response1,
Standard1
Response1,
Standard1
Response1,
Standard1
Response1,
Standard1
D2
Plywood 1
2.2
High
114
Low
11
Low
0.3
High
Plywood 2
3.0
Low#
21
Low
74
Low
1.0
High
Plywood 3
2.6
High
104
Low
44
Low
0.2
High
Plywood 4
3.3
High
102
Low
39
Low
0.9
High
Plywood 5
4.9
High
129
Low
55
Low
0.3
High
HDPE plastic 1
--
--
9.2
High
15
High
21
High
HDPE plastic 2
--
--
0
High
15
High
16
High
HDPE plastic 3
--
--
10
High
20
High
7.8
High
HDPE plastic 4
—
—
16
High
20
High
14
High
HDPE plastic 5
--
--
13
High
15
High
12
High
26
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Table 7. EMPA Degradation Product Recovery at Environmental Condition 1* (continued)
Extraction Time (Weathering Period)
Material and
Replicate
4 days
% EMPA
7 days
% EMPA
14 days
% EMPA
28 days
% EMPA
Response1,
Standard1
Response1,
Standard1
Response1,
Standard1
Response1,
Standard1
D2
Ceiling tile 1
--
--
0
High
--
--
--
--
Ceiling tile 2
--
--
0
High
--
--
--
--
Ceiling tile 3
--
--
8.2
High
--
--
--
--
Ceiling tile 4
--
--
0
High
--
--
--
--
Ceiling tile 5
--
--
0
High
--
--
--
--
Silanized glass 1
--
--
--
--
0
Low
1.1
High
Silanized glass 2
--
--
--
--
4.8
Low
2.0
High
Silanized glass 3
--
--
--
--
0
Low
0.5
High
Silanized glass 4
--
--
--
--
0
Low
0.5
High
Silanized glass 5
—
—
—
—
0
Low
0
High
D1S
HDPE plastic 1
--
--
--
--
7.7
High
11
High
HDPE plastic 2
--
--
--
--
7.6
High
10
High
HDPE plastic 3
--
--
--
--
7.5
High
2.8
High
HDPE plastic 4
--
--
--
--
8.8
High
8.9
High
HDPE plastic 5
--
--
--
--
8.1
High
8.6
High
* Detections (semi-quantitative) of D2 and D1 from test coupons; detections did not occur at other weathering times
or materials.
' The percent of the applicable standard peak area for D2 or Dl.
i The low EMPA standard was 10 |ig/mL. and the high EMPA standard was 81 |ig/mL.
# This sample was the only plywood replicate reanalyzed using the low VX curve and was thus the only replicate
based on the low EMPA standard.
? In some cases Dl was not detected in the associated EMPA standard, so it was not possible to semi-quantitatively
detect Dl from the test coupons specifically: unsealed concrete (at two days), plywood (at four, seven and 14 days),
rubber escalator handrail (at two days), HDPE plastic (at two days), ceiling tile (at two days), and silanized glass (at
two days).
- = D2 or Dl was not detected on any replicate.
3.2.2 Environmental Condition 2
The second environmental condition evaluated was 10 ± 3 °C, 40 ± 5% RH, with one chamber
volume of air exchanged per hour. The target temperature was consistently maintained and
ranged from 8.9 °C to 12.2 °C throughout the study as measured by the Vaisala probe and shelf-
specific HOBO data loggers.
The RH data are presented in Table 8 and Appendix B. As shown in Table 8, which presents
summaries of the shelf-specific HOBO data loggers that collected RH measurements at five min
intervals, the mean RH was above the target level at 30 min (52.4% RH) and at seven hours
(47.1% RH); all other mean RH levels were within the target range of 35% to 45% RH. The RH
became elevated during test initiation when the chamber was opened for a period of time to
allow the VX to be brought into the chamber for coupon spiking. The RH returned to the target
RH level relatively quickly after spiking (Appendix B). On May 10, 2016, the RH level nearly
27
-------
reached 65%; during this time, corrective action was being taken to reverse the trend of
increasing RH, but the bypass valve on the Nafion® humidification tube was inadvertently turned
the wrong way increasing the air flow through the humidifier. This error was quickly identified,
and the bypass valve was turned the correct way to introduce drier air into the chamber. As
shown in Appendix B, other instances of relatively minor or brief RH deviations from the target
level occurred. In some instances, these events were likely associated with the opening of the
chamber to remove samples.
Table 8 also estimates the amount of time the samples were above and below the target RH
levels. The mean RH at 30 min exceeded the target RH level for the entire 30 min duration. For
the seven-hour test, the RH target level was exceeded for 50% of the time. For all other tests,
relatively small portions of the weathering period (<12%) were outside the target RH range.
Table 8. Relative Humidity during Environmental Condition 2 Testing
Measurement
30 min
7 hours
Extraction Time (Weathering Period)
1 day 4 days 7 days 14 days
21 days
35 days
Minimum RH (%)
50.5
41.2
34.9
35.3
32.7
33.0
30.0
29.8
Mean RH (%)
52.4
47.1
39.4
40.5
38.5
40.3
40.3
40.3
Maximum RH (%)
53.4
59.6
56.3
57.7
55.7
63.0
61.9
63.0
Estimated Time RH
30
3.5
2.3
3.0
2.4
19.8
21.2
25.7
was Above the
min
hours
hours
hours
hours
hours
hours
hours
Upper Limit (45%)*
(100%)
(50%)
(9.7%)
(3.1%)
(1.4%)
(5.9%)
(4.2%)
(3.1%)
Estimated Time RH
was Below the
Lower Limit
(35%)*
11.3
hours
19.6
hours
35.3
hours
36.3
hours
(6.7%)
(5.8%)
(7.0%)
(4.3%)
Note: Based on test/shelf-specific RH measured with HOBO data loggers during the weathering periods only. Lower
and higher designations are used to indicate the amount of time below or above the target RH level.
* Results are presented as time, i.e., in min or hours, and as a percentage of the weathering period; estimates of time
above or below RH limits were made based on RH measurements rounded to whole numbers.
-- RH was not below the lower limit.
After each weathering period (prior to extraction), the physical appearance of the coupons was
noted (Table 9). Unsealed concrete and plywood were initially observed at 30 min and were
described as having a "soak" spot, either dark or faint in color, where the VX was applied.
Subsequent observations of the unsealed concrete and plywood throughout the entire exposure
included faint and dark spots, but often there were no visible changes to the coupons. The rubber
escalator handrail initially had a "bead" appearance where the VX was applied; this area was
consistently described as being a blister after four days of exposure. The HDPE plastic samples
generally had a "bead" or "pancake" appearance during the entire exposure time. Dark soak
spots were initially observed on all of the ceiling tile coupons, but at the 7-hour extraction time
and after there was no VX visible. On silanized glass, VX initially had a "pancake" appearance.
Instances of the VX having a "spread" appearance in contrast to a well-defined pancake
appearance occurred during the seven-hour through 21-day exposure durations. The VX on
28
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silanized glass began to appear dry in some cases at seven days and these observations continued
until all coupons appeared dry or hazy at 35 days.
Table 9. Observations Associated with Environmental Condition 2* across Replicates
Material
30 min
7 hours
Extraction Time (Weathering Period)
1 day 4 days 7 days 14 days
21 days
35 days
Unsealed
concrete
Spread;
soak;
dark spot;
faint spot
Dark Spot;
no VX
visible
No VX
visible
No VX
visible
Faint spot;
no VX
visible
No VX
visible
No VX
visible
No VX
visible
Plywood
Soak;
dark spot
Faint spot
Faint spot;
no VX
visible
Faint Spot;
no VX
visible
No VX
visible
Faint spot;
no VX
visible
No VX
visible
Faint Spot;
no VX
visible
Rubber
escalator
handrail
Bead
Bead
Bead
Blister
Blister
Blister
Blister
Blister
HDPE
plastic
Bead
Bead;
pancake
Bead
Pancake
Pancake
Pancake
Pancake
Pancake;
wet
Ceiling
tile
Soak; dark
spot
No VX
visible
No VX
visible
No VX
visible
No VX
visible
No VX
visible
No VX
visible
No VX
visible
Silanized
glass
Pancake
Pancake;
spread
Pancake;
spread; wet
Pancake;
spread; wet
Spread;
wet;
dry spot
Pancake;
spread;
wet;
dry spot
Pancake;
spread;
wet;
dry spot
Hazy;
dry spot
* Differing observations (e.g., dark spot versus no VX visible) occurred on different replicate coupons.
Observations were only recorded for each coupon replicate prior to extraction; repeated observations over time were
not documented for the same replicate coupon.
None of the breakthrough control coupons (i.e., spiked unsealed concrete and ceiling tile
coupons placed on M8 paper) indicated the presence of VX via a color change (i.e., the VX did
not migrate through these especially porous coupons). The unsealed concrete and ceiling tile test
coupons were therefore extracted along with the PTFE disks on which they were placed.
The mean spike control recoveries for VX during testing at Environmental Condition 2 were
1880 |ig from the hexane spike controls and 2073 |ig from the acetone spike controls. Hexane
was used as the extraction solvent for unsealed concrete, rubber escalator handrail, HDPE
plastic, ceiling tile, and silanized glass. Acetone was used as the extraction solvent for plywood.
The mean VX recovery from the hexane spike controls (1880 |ig) was lower than expected,
because one of the spike control replicates had a lower recovery (1240 |ig) compared to the other
four replicates with VX recoveries ranging from 1765 |ig to 2280 |ig. No observations were
made at the time of testing to explain the lower recovery. For rubber escalator handrail, HDPE
plastic, ceiling tile, and silanized glass, mean VX recoveries were sometimes higher than the
theoretical recoveries obtained from the spike controls, especially within the first day of testing.
The amount of VX recovered from the various materials over time is presented in Figure 6 and
Table 10. After a 30-min weathering period, the mean VX recovery was >1940 |ig for all
29
-------
materials except unsealed concrete, which had a mean VX recovery of 1050 |ig. The VX
recoveries decreased rather steadily for unsealed concrete, but VX remained detectable after 35
days with a mean VX recovery of 78 |ig. The mean VX recoveries from the other materials
remained >1128 |ig for at least four days. For plywood and silanized glass, the mean VX
recoveries remained >1026 |ig after seven days but then decreased to levels lower than those
recovered from unsealed concrete at 35 days (<52 |ig). The VX recoveries from rubber escalator
handrail, HDPE plastic, and ceiling tile were >1015 |ig after 14 days and remained >391 |ig for
the entire study duration. The mean VX recovery from rubber escalator handrail was noticeably
lower at seven days (427 |ig) than observed at four days (1128 |ig) and 14 days (1015 |ig). The
reason for this lower result is unknown, but a similar incidence of lower VX recovery from
rubber escalator handrail also occurred at Environmental Condition 1, where the mean VX
recovery at two days (731 |ig) was lower than the recovery at one day (1227 |ig) and four4 days
(908 |ig) (see Table 6).
Unsea ed concrete
Plywood
Rubber esca ator handrai
HDPE plastic
Ceiling tile
Silanized glass
30 minutes 7 hours
1 day 4 days 7 days 14 days
Extraction Time (Weathering Period)
21 days 35 days
Figure 6. VX recovery at Environmental Condition 2 (error bars equal plus one standard
deviation). Initial spiked VX amount is 1900 jig except for plywood (2100 jig).
30
-------
Table 10. VX Recovery at Environmental Condition 2
Material
Measure of
VX Recovery
30 min
E
7 hours
Extraction Time (Weathering Period'
1 day 4 days 7 days 14 days
21 days
35 days
Unsealed
concrete*
Mean (jig)
1050
811
438
263
215
111
54
78
SD (jig)
394
275
154
92
96
72
25
40
CV (%)
38
34
35
35
45
65
46
52
FOD
5/5
5/5
5/5
5/5
5/5
5/5
5/5
5/5
PB (jig)
<2.5
<2.5
<2.5
<2.5
9.3
10
3.1
5.7
Plywood1^
Mean (jig)
1940
1777
1729
1354
1026
456
151
52
SD (jig)
72
75
134
104
211
87
31
11
CV (%)
3.7
4.2
7.8
7.7
21
19
20
22
FOD
5/5
5/5
5/5
5/5
5/5
5/5
5/5
5/5
PB (jig)
<2.5
<2.5
<2.5
16
16
32
29
16
Rubber
escalator
handrail*
Mean (jig)
2143
1917
1886
1128
427
1015
553
473
SD (jig)
106
164
317
458
87
285
264
229
CV (%)
4.9
8.5
17
41
20
28
48
48
FOD
5/5
5/5
5/5
5/5
5/5
5/5
5/5
5/5
PB (jig)
<2.5
<2.5
2.7
27
50
44
32
39
HDPE
plastic*
Mean (jig)
2106
2207
2062
1773
1955
1825
1206
391
SD (jig)
116
41
111
215
59
131
390
81
CV (%)
5.5
1.9
5.4
12
3.0
7.2
32
21
FOD
5/5
5/5
5/5
5/5
5/5
5/5
5/5
5/5
PB (jig)
<2.5
<2.5
<2.5
<2.5
<2.5
<2.5
3.2
<2.5
Ceiling
tile*
Mean (jig)
1952
2092
2035
1782
1470
1396
967
435
SD (jig)
165
156
64
262
250
73
136
56
CV (%)
8.4
7.5
3.1
15
17
5.2
14
13
FOD
5/5
5/5
5/5
5/5
5/5
5/5
5/5
5/5
PB (jig)
<2.5
<2.5
4.4
10
16
14
25
29
Silanized
glass*
Mean (jig)
2113
2084
1997
1413
1054
715
450
5.9
SD (jig)
65
26
146
693
953
616
697
3.6
CV (%)
3.1
1.3
7.3
49
90
86
155
61
FOD
5/5
5/5
5/5
5/5
5/5
5/5
4/5
4/5
PB (jig)
<2.5
<2.5
<2.5
<2.5
<2.5
<2.5
<2.5
<2.5
SD = standard deviation; five replicate coupons were extracted per material and weathering period.
CV = coefficient of variation.
FOD = frequency of detection (number of coupons above the quantitation limit/total number of coupons). For results
less than the quantitation limit. 2.5 jig was used for the calculation of summary statistics.
PB = procedural blank; all laboratory blanks were non-detect for VX (<2.5 jig). The VX detections on the PBs were
likely associated with VX volatilization and subsequent deposition/adsorption.
< = all available results were less than the quantitation limit.
* The spike control (hexane with IS and DIC) associated with these materials had a mean VX recovery of 1880 jig:
one of the replicates had a comparatively low VX recovery (1240 jig): a definitive cause was not identified.
' The spike control (acetone with IS and DIC) associated with plywood had a mean VX recovery of 2073 jig.
The VX recoveries associated with silanized glass were associated with the highest CVs (e.g.,
from 86% to 155% over 7 to 21 days), while the CVs were <65% in all other cases (Table 10).
Interestingly, the VX descriptions on silanized glass for these weathering times (Table 9)
covered a wide range of appearances from well formed "pancake" shapes, to coupons that
remained wet with VX spread across the coupon, to an apparently dry VX residue on the coupon.
31
-------
As shown in Table 11, VX recoveries within a given weathering period were lowest where the
coupon was described as being dry, higher when the coupons were described as having a wet
appearance, and highest when the coupons retained VX in a "pancake" shape. The visual
descriptions may reflect the amount of agent volatilization/degradation that has occurred with
silanized glass coupons appearing dry having the most VX loss, while VX retaining the
"pancake" appearance is associated with the lowest amount of attenuation. Similar relationships
between the VX appearance on silanized glass coupons and the amount of VX recovered also
occurred with Environmental Condition 1 at four and seven days (data not presented). Other
researchers have reported relationships between CWA drop size and evaporation rates and
degradation rates. For example, Jung and Lee (2014) reported the evaporation rate of sulfur
mustard from aluminum and stainless steel increased linearly with increasing drop size. Wagner
et al. (2004) found that the degradation rate of larger VX droplets on concrete was slower than
for smaller droplets. When Wagner et al. (2004) dissolved a large droplet of VX in hexane and
uniformly distributed the VX across the concrete surface, the degradation rate increased similar
to the degradation rate associated with the smaller droplets. For the current study, the reason for
VX presenting differently on silanized glass is not known.
Table 11. VX Recoveries from Silanized Glass at 7,14, and 21 Days at Environmental
Condition 2
Silanized
Glass
Replicate
Extraction Time (Weathering Period)
7 Days
VX
Description* Recovery
(M-g) '
14 Days
VX
Description* Recovery
(Hg) '
21 Days
VX
Description* Recovery
(Hg) '
1
Wet; spread
1781
Wet; spread
644
Dry Spot
188
2
Dry spot
3.2
Dry spot;
spread
6.3
Dry Spot
<2.5
3
Wet; spread
1827
Pancake
1582
Dry Spot
4.0
4
Wet; spread
1637
Dry spot;
spread
313
Wet; Spread
394
5
Dry spot
21
Wet; spread
1029
Pancake
1663
* Observations were recorded for each coupon replicate prior to extraction; repeated observations over time were
not documented for the same replicate coupon.
Relatively low levels (< 50 |ig) of VX were recovered from the procedural blanks (unspiked
coupons held in the test chamber) (Table 10). As with the testing conducted under
Environmental Condition 1, VX was only recovered from the porous/permeable material
procedural blanks and not from the silanized glass procedural blanks. The porous materials
appear capable of adsorbing vaporous VX that might have volatilized from the spiked coupons.
VX was not detected from any of the laboratory blanks, which are unspiked coupons never
placed inside the test chamber.
As noted in Section 2.8.8, sample extracts were also analyzed to semi-quantitatively estimate D1
and D2, which are degradation products of VX by way of EMPA degradation. As shown on
Table 12, D2 was detected from plywood at 7, 14, 21, and 35 days and detected from HDPE
32
-------
plastic at 21 and 35 days. As footnoted in Table 12, in a few analytical runs D1 was not detected
in the associated EMPA standard; in these instances, the response from D1 was simply
insufficient to provide a peak. The footnote is intended to document these instances and clarify
that a semi-quantitative response for D1 was not applicable rather than indicating a 0% response.
Table 12. EMPA Degradation Product Recovery at Environmental Condition 2*
Material and
Replicate
Extraction Time (Weathering Period)
7 days
% Response1'
14 days
% Response1'
21 days
% Response1,
35 days
% Response1,
D2
Plywood 1
0
1.3
2.2
0.6
Plywood 2
0
5.2
3.3
0.9
Plywood 3
0
1.3
3.2
1.0
Plywood 4
0.3
1.5
3.3
1.3
Plywood 5
0
2.0
4.3
1.7
HDPE plastic 1
--
--
0.8
4.6
HDPE plastic 2
--
--
0.7
4.0
HDPE plastic 3
--
--
0
4.7
HDPE plastic 4
--
--
3.9
3.1
HDPE plastic 5
--
--
0.3
4.2
* Detections (semi-quantitative) of D2 from test coupons; detections did not occur at other weathering times or
materials. D1 was not detected from the test coupons; however, in some cases D1 was not detected in the associated
EMPA standard either, so it was not possible to semi-quantitatively detect D1 from: unsealed concrete (at 30 min
seven hours, and one day), rubber escalator handrail (at 30 min, seven hours, and one day), HDPE plastic (at 30 min,
seven hours, and one day), ceiling tile (at 30 min seven hours, and one day), and silanized glass (at 30 min seven
hours, and one day).
' The percent of the applicable standard peak area for D2; only the high EMPA standard (81 ng/mL) was used.
-- = D2 was not detected on any replicate.
3.2.3 Environmental Condition 3
Environmental Condition 3 was defined as: 35 ± 3 °C, 40 ± 5% RH, with one chamber volume of
air exchanged per hour. The actual temperature as measured by the Vaisala probe and the shelf-
specific HOBO data loggers was consistently maintained within 35 ± 1 °C for all test durations.
Similarly, the actual RH values, when rounded to whole numbers, ranged from 35% to 43%,
which was within the target RH level range. Technically two RH measurements made with the
Vaisala probe (34.99% and 34.69%) were slightly less than the lower RH target of 35%, but
none of the RH measurements made with the HOBO data loggers were below 35%.
After each weathering period (prior to extraction), the physical appearance of the coupons was
noted (Table 13). Unsealed concrete and plywood were initially observed at 30 min and were
described as having a dark "soak" spot where the VX was applied. Subsequent observations of
the unsealed concrete and plywood included faint and dark spots or no visible changes to the
coupons. The rubber escalator handrail initially had a "pancake" appearance where the VX was
applied; this area was consistently described as being a blister after 1 day of exposure. With the
exception of one "wet/spread" observation at 30 min, all HDPE plastic samples were described
as having a "pancake" appearance. Some dark soak spots or stains were initially observed after
33
-------
30 min on the ceiling tile coupons, but subsequent observations were described as no VX visible.
On silanized glass, VX initially had a "pancake" or "wet/spread" appearance. Observations
indicative of the VX becoming dry or hazy began to be reported after one day of weathering, and
in some cases, there was no VX visible on the silanized glass coupons.
None of the breakthrough control coupons (i.e., spiked unsealed concrete and ceiling tile
coupons placed on M8 paper) indicated the presence of VX via a color change (i.e., the VX did
not seep through these especially porous coupons). The unsealed concrete and ceiling tile test
coupons were therefore extracted along with the PTFE disks on which they were placed.
Table 13. Observations Associated with Environmental Condition 3* across Replicates
Material
30 min
4 hours
Extraction Time (Weathering Period)
7 hours 1 day 2 days 3 days
7 days
10 days
Unsealed
concrete
Soak;
dark spot
Dark spot;
no VX
visible
Dark spot;
no VX
visible
Faint spot;
no VX
visible
No VX
visible
No VX
visible
No VX
visible
No VX
visible
Plywood
Soak;
dark spot
Dark spot;
faint spot;
no VX
visible
Faint spot
Faint spot;
no VX
visible
Faint spot;
no VX
visible
No VX
visible
No VX
visible
No VX
visible
Rubber
escalator
handrail
Pancake
Pancake;
Blister
Pancake;
Blister
Blister
Blister
Blister
Blister
Blister
HDPE
plastic
Pancake;
wet; spread
Pancake
Pancake
Pancake
Pancake
Pancake
Pancake
Pancake
Ceiling
tile
Soak;
dark spot;
stain; No
VX visible
No VX
visible
No VX
visible
No VX
visible
No VX
visible
No VX
visible
No VX
visible
No VX
visible
Silanized
glass
Pancake;
wet; spread
Pancake;
wet; spread
Pancake;
wet; spread
Wet;
spread;
hazy;
dry spot;
no VX
visible
Pancake;
hazy;
dry spot
Wet;
spread;
hazy; dry
spot; no
VX
visible
Hazy;
dry spot;
no VX
visible
Hazy;
dry spot;
no VX
visible
* Differing observations (e.g., dark spot versus no VX visible) occurred on different replicate coupons.
Observations were only recorded for each coupon replicate prior to extraction; repeated observations over time were
not documented for the same replicate coupon.
The amount of VX recovered over time is presented in Figure 7 and Table 14. The mean spike
control recoveries for VX during testing at Environmental Condition 3 were 2104 |ig from the
hexane spike controls and 2218 |ig from the acetone spike controls. Hexane was used as the
extraction solvent for unsealed concrete, rubber escalator handrail, HDPE plastic, ceiling tile,
and silanized glass. Acetone was used as the extraction solvent for plywood.
34
-------
30 minutes 4 hours
Unsealed concrete
Plywood
Rubber escalator handrail
HDPE plastic
Ceiling tile
Silanized glass
_L
7 hours 1 day 2 days 3 days
Extraction Time (Weathering Period)
7 days 10 days
Figure 7. VX recovery at Environmental Condition 3 (error bars equal plus one standard
deviation). Initial spiked VX amount is 2100 jig except for plywood (2200 jig).
The mean VX recoveries after 30 min were >1720 |ig for all materials, except unsealed concrete,
which had a mean VX recovery of 659 |ig. VX recovery from unsealed concrete rather steadily
decreased with only one or two replicate coupons detecting VX at seven days and 10 days of
exposure (the associated mean VX recoveries were <6.2 |ig). The mean VX recoveries remained
>1308 |ig for all other materials after seven hours. For plywood, the mean VX recovery
dramatically decreased between seven hours (1631 |ig) and one day (395 |ig); the VX recoveries
from plywood continued to decrease until becoming completely non-detect at 10 days. Similar
decreases in mean VX recovery were associated with HDPE plastic between two days (1455 |ig)
and three days (545 |ig) and silanized glass between seven hours (1653 |ig) and one day (691
|ig). The VX remained detectable from HDPE plastic at low levels (mean VX recovery 7.1 |ig) at
10 days, but VX was not detected from silanized glass at 10 days. The mean VX recoveries at
seven days and 10 days were highest from rubber escalator handrail (159 |ig and 86 |ig,
respectively) and ceiling tile (71 |ig and 18 |ig, respectively).
35
-------
Table 14. VX Recovery at Environmental Condition 3
Material
Measure of
VX Recovery
30 min
E
4 hours
Extraction Time (Weathering Period^
7 hours 1 day 2 days 3 days
7 days
10 days
Unsealed
concrete*
Mean (jig)
659
561
408
192
93
38
3.6
6.2
SD (jig)
223
256
126
91
30
21
1.7
8.3
CV (%)
34
46
31
47
33
57
46
133
FOD
5/5
5/5
5/5
5/5
5/5
5/5
2/5
1/5
PB (jig)
<2.5
4.4
36
12
4.1
20
<2.5
<2.5
Plywood1^
Mean (jig)
1937
1815
1631
395
93
49
3.7
<2.5
SD (jig)
147
100
155
73
80
14
0.39
0
CV (%)
7.6
5.5
9.5
19
86
28
11
0
FOD
5/5
5/5
5/5
5/5
5/5
5/5
5/5
0/5
PB (jig)
<2.5
8.5
19
23
22
33
2.8
<2.5
Rubber
escalator
handrail*
Mean (jig)
1726
1511
1308
805
540
443
159
86
SD (jig)
148
306
511
403
425
244
107
45
CV (%)
8.6
20
39
50
79
55
67
53
FOD
5/5
5/5
5/5
5/5
5/5
5/5
5/5
5/5
PB (jig)
<2.5
6.6
17
41
31
24
14
33
HDPE
plastic*
Mean (jig)
1898
2021
1919
1691
1455
545
22
7.1
SD (jig)
110
53
66
113
173
238
5.4
1.2
CV (%)
5.8
2.6
3.5
6.7
12
44
25
18
FOD
5/5
5/5
5/5
5/5
5/5
5/5
5/5
5/5
PB (jig)
<2.5
3.7
3.6
<2.5
8.7
2.9
<2.5
<2.5
Ceiling
tile*
Mean (jig)
1720
1835
1791
1205
842
460
71
18
SD (jig)
289
251
119
205
152
159
16
5.3
CV (%)
17
14
6.7
17
18
35
23
29
FOD
5/5
5/5
5/5
5/5
5/5
5/5
5/5
5/5
PB (jig)
<2.5
5.7
17
24
55
66
28
10
Silanized
glass*
Mean (jig)
1965
1874
1653
691
454
184
3.0
<2.5
SD (jig)
83
43
537
631
575
247
1.2
0
CV (%)
4.2
2.3
32
91
127
135
39
0
FOD
5/5
5/5
5/5
3/5
5/5
4/5
1/5
0/5
PB (jig)
<2.5
<2.5
<2.5
<2.5
<2.5
<2.5
<2.5
<2.5
SD = standard deviation; five replicate coupons were extracted per material and weathering period.
CV = coefficient of variation.
FOD = frequency of detection (number of coupons above the quantitation limit / total number of coupons). For
results less than the quantitation limit. 2.5 jig was used for the calculation of summary statistics.
PB = procedural blank; all laboratory blanks were non-detect for VX (<2.5 jig). The VX detections on the PBs were
likely associated with VX volatilization and subsequent deposition/adsorption.
< = all available results were less than the quantitation limit.
* The spike control (hexane with IS and DIC) associated with these materials had a mean VX recovery of 2104 jig.
' The spike control (acetone with IS and DIC) associated with plywood had a mean VX recovery of 2218 jig.
Relatively low levels (< 66 jig) of VX were recovered from the procedural blanks (unspiked
coupons held in the test chamber) (Table 14). As with the testing conducted under
Environmental Conditions 1 and 2, VX was only recovered from the porous/permeable material
procedural blanks and not from the silanized glass procedural blanks. The porous or permeable
materials appear capable of adsorbing VX that might have volatilized from the spiked coupons.
36
-------
VX was not detected from any of the laboratory blanks, which are unspiked coupons never
placed inside the test chamber.
Sample extracts were also analyzed to semi-quantitatively estimate D1 and D2, which are
degradation products of VX by way of EMPA degradation. As shown on Table 15, D2 was
detected from plywood, HDPE plastic, ceiling tile, and silanized glass at seven and 10 days. D2
was also detected earlier from plywood (after one, two, and three days) and HDPE plastic (after
two and three days). D1 was only detected from HDPE plastic after seven and 10 days.
Table 15. EMPA Degradation Product Recovery at Environmental Condition 3*
Material and
Replicate
Extraction Time (Weathering Period)
1 day
% Response1'
2 days
% Response1'
3 days
% Response1,
7 days
% Response1,
10 days
% Response1,
D2
Plywood 1
1.4
0
2.9
1.8
1.0
Plywood 2
1.2
3.7
1.5
2.2
1.2
Plywood 3
1.9
1.0
3.8
1.2
1.7
Plywood 4
1.1
0
3.7
1.2
1.3
Plywood 5
2.2
5.3
1.5
1.2
1.0
HDPE plastic 1
--
0.3
3.5
87
6.6
HDPE plastic 2
--
0
2.5
111
11
HDPE plastic 3
—
0
4.1
51
7.2
HDPE plastic 4
--
0
14
65
11
HDPE plastic 5
--
0
3.2
85
14
Ceiling tile 1
--
--
--
2.6
0.1
Ceiling tile 2
--
--
--
1.0
0.1
Ceiling tile 3
--
--
--
0
0.1
Ceiling tile 4
--
--
--
0
0.2
Ceiling tile 5
--
--
--
1.0
0.1
Silanized glass 1
--
--
--
0
0.7
Silanized glass 2
--
--
--
12
0
Silanized glass 3
--
--
--
0
0.3
Silanized glass 4
--
--
--
0
0
Silanized glass 5
—
—
—
2.4
0
Dl
HDPE plastic 1
--
--
--
57
1.9
HDPE plastic 2
--
--
--
77
2.9
HDPE plastic 3
--
--
--
46
2.8
HDPE plastic 4
--
--
--
50
3.6
HDPE plastic 5
--
--
--
58
4.3
* Detections (semi-quantitative) of D2 and D1 from test coupons; detections did not occur at other weathering times
or materials.
' The percent of the applicable standard peak area for D2 or Dl; only the high EMPA standard (81 ng/mL) was
used.
- = D2 or Dl was not detected on any replicate.
37
-------
3.3 ANOVA Results
The results of applying the log-linear ANOVA model presented in Section 2.9 above to the
observed (log-transformed) residual VX mass measurement data to test the three sets of
statistical hypotheses of interest were as follows:
Test #1:
• Null hypothesis'. No decline occurs in mean recovered VX over time.
• Alternative hypothesis: Mean recovered VX declines over time.
The (declining) time trend was highly statistically significant overall and for each of the three
environmental conditions and six material types (p<0.0001 for each test), meaning the null
hypothesis can be rejected in favor of the alternative.
The overall mean slope estimate (A + /? + f) was -0.01141 (with standard error 0.00027). Thus, at
T hours following spiking, the model-predicted average residual mass of VX (|ig) is some
multiple of e~a01140T = (0.9887)7
The environmental condition-specific slope estimates (A+f+ft) were as follows:
• Environmental Condition #1 (25 ± 3 °C): -0.00791 (with standard error 0.00028)
• Environmental Condition #2 (10 ± 3 °C): -0.00335 (with standard error 0.00022)
• Environmental Condition #3 (35 ± 3 °C): -0.02230 (with standard error 0.00073)
The material-specific slope estimates (A, + P + y ¦) were as follows (each having standard error
0.00046):
• Unsealed concrete: -0.01134
• Plywood: -0.01328
• Rubber escalator handrail: -0.00824
• HDPE plastic: -0.01093
• Ceiling tile: -0.00973
• Silanized glass (reference material): -0.01490
All of these estimates are negative, implying a decline in residual mass over time. The larger the
slope estimate in absolute value, the greater the rate of decline in the hours immediately
following spiking.
Test #2:
• Null hypothesis'. The mean rate of VX loss does not change among different
environmental conditions (temperatures).
38
-------
• Alternative hypothesis: The mean rate of VX loss differs among environmental
conditions (temperatures).
The ANOVA model fitting determined that significant differences existed between the three
environmental condition-specific slopes {X + f + p^ (p<0.0001), indicating the rate of decline in
residual mass measurement of VX over time differed significantly among the three
environmental conditions. These estimates were given above in the results for Test #1:
Environmental Condition #3 had the largest slope in absolute value, about 2.8 times the value of
the next-highest slope, for Environmental Condition #1, which in turn was twice the value of the
slope for Environmental Condition #2. To determine which of these three slopes differed
significantly from each other, pairwise differences among each of these three slopes (i.e.,
differences among the values) were statistically compared at an overall 0.05 level (i.e., each
test performed at a 0.05/3=0.0167 level). All three pairs differed significantly from each other
(pO.OOOl).
Statistical tests were also performed to determine whether the mean VX residual mass value
(across time) differed among the three environmental conditions. Because the interaction term
(oM)ij was statistically significant (p<0.0001), the significance of the mean attenuation effect
was dependent on the material type. Therefore, statistical comparisons between pairs of
attenuations were done by material type, with the overall significance level among all three pairs
of the three environmental conditions being no higher than 0.05 within each material type (i.e.,
each test performed at a 0.05/3=0.0167 level). The following pairs of environmental conditions
differed significantly in their mean residual mass values for the following material types:
• Unsealed concrete: Environmental Condition 1 vs. 2
• Plywood: Environmental Condition 1 vs. 2, 2 vs. 3
• Rubber escalator handrail: Environmental Condition 2 vs. 3
• Silanized glass: Environmental Condition 1 vs. 3, 2 vs. 3
Test #3:
• Null hypothesis: The mean rate of VX loss does not vary among different materials.
• Alternative hypothesis: The mean rate of VX loss does vary among different materials.
The ANOVA model fitting determined that significant differences existed between the six
material-specific slopes {X + p + Yj) (pO.OOOl), indicating that the rate of decline in residual
mass measurement of VX over time differed significantly among the three environmental
conditions. These estimates were given above in the results for Test #1 (and are repeated below
in Table 16): the largest slope estimate in absolute value (for silanized glass, the nonporous
reference material) was approximately 80% higher than the smallest estimated slope in absolute
value (for rubber escalator handrail). To determine which of these six slopes differed
significantly from each other, pairwise differences in these slopes (i.e., differences among the y,
values) were statistically compared at an overall 0.05 level (i.e., each test performed at a
0.05/15=0.0033 level).
39
-------
Table 16. ANOVA Test Results for Mean Rate of VX Loss (Slope Estimate) from Different
Materials (among the Three Environmental Conditions Tested)
Material
Material-
Specific Slope
Estimates
Vertical Lines Connect Materials
whose Estimates do not Differ
Significantly
Silanized glass (reference material):
-0.01490
Plywood
-0.01328
Unsealed concrete
-0.01134
HDPE plastic
-0.01093
Ceiling tile
-0.00973
Rubber escalator handrail
-0.00824
As shown in Table 16, the rate of decline for silanized glass differs significantly from each of the
porous/permeable materials except plywood. In turn, the rate of decline for rubber escalator
handrail differed significantly from all but ceiling tile.
Statistical tests were also performed to determine whether the mean VX residual mass value
(across time) differed among the six materials. Because the interaction term (oM)y was
statistically significant (p<0.0001), the significance of the mean attenuation effect was dependent
on the environmental condition. Therefore, statistical comparisons between pairs of materials
were done by environmental condition, with the overall significance level among all 15 pairs of
the six material types being no higher than 0.05 within each environmental condition (i.e., each
test performed at a 0.05/15=0.0033 level). The following pairs of materials differed significantly
in their mean residual mass values for the following environmental conditions (Table 17):
• Environmental Condition 1:
o [plywood and unsealed concrete] versus all other materials (with the exception
of plywood versus silanized glass).
• Environmental Condition 2:
o unsealed concrete versus all other materials (with the exception of rubber
escalator handrail);
o rubber escalator handrail versus [HDPE plastic and plywood],
• Environmental Condition 3:
o rubber escalator handrail versus all other materials (with the exception of
ceiling tile)
o [plywood, silanized glass, and unsealed concrete] versus [ceiling tile and
HDPE plastic]
o plywood versus unsealed concrete.
40
-------
Table 17. ANOVA Test Results Identifying Pairs of Materials with Significantly Different
Mean Residual Mass under Identified Environmental Conditions
Material
Material
Plywood
Unsealed
concrete
HDPE
plastic
Ceiling tile
Rubber
escalator
handrail
Silanized Glass
El, E2
E3
E3
E3
Plywood
El, E2, E3
El, E3
El, E3
El, E2, E3
Unsealed concrete
El, E2, E3
El, E2, E3
El, E3
HDPE plastic
E2, E3
Ceiling tile
El, E2, E3: Environmental Condition 1, 2, 3
41
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4.0 Quality Assurance/Quality Control
4.1 Control of Monitoring and Measuring Devices
Quality control requirements and results are shown in Table 18 and includes checks of the
measurement methods for temperature, RH, time, volume, spike controls, IS, VX recovery from
silanized glass, and laboratory blanks. Attainment of these data quality indicator results limited
the amount of error introduced into the investigation results.
Table 18. Quality Control Requirements and Results
Parameter
Measurement
Method
Data Quality Indicators
Results
Temperature,
°C
Thermometer
Compared against calibrated
National Institute of Standards and
Technology (NIST)-traceable
thermometer once before testing,
agree ±1 °C
At each environmental
condition, the HOBO data
loggers were generally
within ±1 °C of the NIST-
traceable Vaisala
instrument.
RH, %
Hygrometer
Compared against calibrated
NIST-traceable hygrometer once
before testing, agree ±10% (full
scale)
At each environmental
condition, the HOBO data
loggers were generally
within ±5% of the NIST-
traceable Vaisala
instrument.
Time,
second
Timer/data
logger
Compared against calibrated
NIST-traceable timer once before
testing; agree ±2 seconds/min.
Deviation of 0 second/min
Volume, (J.L
Repeating
dispenser/syringe
Repeating dispenser/syringe was
checked for accuracy and
repeatability one time before use
by determining the mass of water
delivered. The syringe was
considered acceptable if the range
of observed masses for five
droplets was ±10% of expected.
Ten measurements were
made with tolerances
(percent errors) of 4.84,
9.85, 0.17, 10.19, 9.85,
9.85, 9.85, 0.17, 0.17, and
9.85%.
Spike control
GC/MS
The mean of the spike controls
included with each day of testing
should be within 70% to 120% of
the target application.
The mean spike control
recoveries (for hexane and
acetone separately) were
within 70% to 120% of
the theoretical recoveries.
42
-------
Table 18. Quality Control Requirements and Results (continued)
Parameter
Measurement
Method
Data Quality Indicators
Results
is,
naphthalene-
d8
Extraction,
GC/MS
The mean of the IS quantity
included with each day of testing
should be within 70% to 120% of
the expected mass.
Every sample's IS
response was compared to
the mid-point standard.
Anything outside the
specification was flagged
and re-run.
VX on
silanized
glass with
immediate
extraction,
|ig/m L
Extraction,
GC/MS
The mean percent recovery for a
known quantity of VX added to
silanized glass coupons must fall
within the range of 70% to 120%
of the spike control and have a CV
of <30% between replicates.
The mean VX recovered
from silanized glass (after
a 30-min weathering
period) was within 70% to
120% of the VX
recovered from the
associated spike controls
and the CVs were <30%
between replicates, except
for Environmental
Condition 1 when the CV
was 55%.
VX on
laboratory
blank
coupons,
|ig/m L
Extraction,
GC/MS
Laboratory blanks (coupons
without applied VX maintained
outside the testing hood) should
have <1% of the amount of
analyte compared to that found on
spike controls.
No measurable VX
detected on laboratory
blank coupons.
4.2 Equipment Calibrations
The instrumentation used to quantify VX and semi-quantify D1 and D2 from the material
extracts is identified in Section 2.8. The equipment needed for the analytical methods was
maintained and operated according to the quality requirements and documentation of the Battelle
HMRC. All equipment was calibrated with appropriate standards and at the frequency specified
in Table 19.
GC/MS calibration ranged from 0.1 |ag/m L to 125 |ig/mL. To accommodate accurate analysis
over this broad range, two separate calibration curves were generated - a "low" curve ranging
from 0.1 |ig/mL to 10 |ig/mL, and a "high" curve ranging from 5.0 |ig/mL to 125 |ig/mL. Each
curve was constructed using five distinct calibration levels. Range of each curve and selection of
the specific calibration points included in each curve were determined based on general GC/MS
performance in analysis of VX in hexane and acetone as well as on the observed quadratic
response nature of VX. A quadratic regression (coefficient of determination [r2] >0.990) curve fit
was applied to the calibration data. Any sample exceeding the upper calibration limit of the high
curve would have been diluted to a concentration within the calibration range and reanalyzed.
However, no such case occurred. Sample results below the high curve lower calibration limit
43
-------
were analyzed against the low curve. Sample results below the low curve lower calibration limit
were reported as < 0.1|ig/mL. The GC/MS was tuned daily. A tune check was performed before
running each batch using decafluorotriphenylphosphine. A 12-hour tune time was not employed.
Table 19. Equipment Calibration Schedule
Equipment
Frequency
Calibrated pipette and
repeating dispenser/syringe
Prior to the investigation and every six months thereafter
Calibrated
hygrometer/thermometer
Prior to the investigation and annually thereafter
GC/MS
Beginning of each batch of test samples (calibration curve) and a
calibration verification standard after every five samples and at the
end of a batch of samples
Following analysis of the calibration standards at the beginning of each analytical run, a solvent
blank sample (e.g., hexane with IS and DIC or acetone with IS and DIC) was analyzed to
confirm that no VX carryover was occurring. Solvent blank sample analysis results were below
the value of the lowest calibration standard.
Independently prepared CCV standards were analyzed prior to sample analysis, following every
five samples, and at the end of each batch of samples. Two CCV concentrations were used, one
of which was equal to the low calibration standard and the other(s) within the calibration range.
Measured CCV concentration was required to fall within 35% of the nominal concentration for
the lowest level CCV used and within 20% of the nominal concentration for all other CCVs for
test sample extract VX analysis results to be considered valid. Samples analyzed prior to or
following CCVs that were outside acceptance limits were reanalyzed.
Neat VX was used to create calibration standards encompassing the appropriate analysis
range. Calibration standards were kept and used for no longer than six months from the date
of creation. CCV standards were kept and used for no longer than one month from the date of
creation. The GC was recalibrated if the r2 from the regression analysis of the standards was
<0.98.
Limits were placed on the percent bias observed in the standards.
Percent bias = x 100% (5)
where:
R = expected value from calibration curve
C = observed value from standard.
The percent bias for the low standard required <25%, and the percent bias for the remaining
standards required <15%.
44
-------
As stated above, one CCV standard was ran for every five samples. The percent bias for the low
CCV standard was required to be <35%, and the percent bias for the remaining CCV standards
had to be <20%. Additionally, every 10th test sample extract was immediately reinjected and
analyzed following the original. The result from the reanalysis of every 10th sample was used
strictly as an additional confirmation to the analyst of adequate GC performance. The reanalysis
result was required to fall within 20% of the result of the original analysis of the sample (see
Table 19). The 10th sample reanalysis results were included only in the primary raw analysis data
generated by the analyst and excluded from calculations and reported data (only the original
analysis result was used for calculation and reporting purposes). Criteria for evaluation of the GC
performance are shown in Table 20.
CCV standards or test sample extract reinjections/reanalyses that did not meet the above analysis
results quality criteria were flagged, and all test sample extracts analyzed prior to and following
the non-compliant standard (to the next compliant standard) were reanalyzed. All reported data
(data included in calculations and attenuation performance summaries) were generated from
analyses that met the criteria described in Table 20.
Table 20. Gas Chromatography Performance Parameters and Acceptance Criteria
Parameter
Criterion
Coefficient of determination (r2)
>0.99
% bias for the lowest calibration standard
<25%
% bias for remaining calibration standards (except lowest
standard)
<15%
Solvent blank sample
< lowest calibration standard
% bias for the lowest CCV
<35%
% bias for remaining CCVs (except lowest CCV)
<20%
Differences between replicate samples (10th sample reanalysis)
<20%
4.3 Technical Systems A udit
The Quality Assurance (QA) Officer performed a technical systems audit (TSA) at the HMRC
facility in West Jefferson, Ohio, during the first day of testing at Environmental Condition 2. The
purpose of the TSA was to ensure that testing was performed in accordance with the Quality
Assurance Project Plan (QAPP). The QA Officer reviewed the investigation methods, compared
test procedures to those specified in the QAPP (and the associated amendments), and reviewed
data acquisition and handling procedures. The QA Officer did not identify any findings that
required corrective action.
4.4 Performance Evaluation A udit
A performance evaluation audit was conducted as summarized in Table 21. Acceptable
tolerances were volume (±10%), time (±1 second/min), chemical mass (>85%), IS (±10%),
temperature (±1 °C), and RH (±10%).
45
-------
Table 21. Performance Evaluation Results
Parameter
Audit Procedure
Expected
Tolerance
Results
Volume
Syringe used for dispensing chemical
agent was checked for accuracy and
repeatability one time before use by
determining the mass of water delivered
±10%
Ten measurements were made with
tolerances (percent errors) of 4.84,
9.85,0.17, 10.19,9.85,9.85,9.85,
0.17,0.17, and 9.85%.
Time
Compared time to independent NIST-
traceable timer one time before use
±1
second/min
0 second/min
Compound
mass
Used GC/MS to determine mass of VX
delivered as 2 |_iL droplet into 25 mL of
hexane and acetone and compared to
target application level one time
>85% of
spike target
All mean spike control VX
recoveries were >85% of the target
spike amount; only one replicate (a
hexane spike control from
Environmental Condition 2) had a
VX recovery <85% (64%).
IS
Used GC/MS to measure from a
secondary source and compare to the
primary source one time
±10%
1.9% (relative percent difference)
Temperature
Compared against calibrated NIST-
traceable thermometer one time before
use
±1 °C
At each environmental condition,
the HOBO data loggers were
generally within ±1 °C of the
NIST-traceable Vaisala instrument.
RH
Compared against calibrated NIST-
traceable hygrometer one time before use
±10%
At each environmental condition,
the HOBO data loggers were
generally within ±5% of the NIST-
traceable Vaisala instrument.
4.5 Data Quality Audit
The QA Manager audited at least 10% of the investigation data and traced the data from initial
acquisition, through reduction and statistical comparisons, to final reporting. All data analysis
calculations were checked.
4.6 Deviations
Two deviations were noted for this project:
• The purity of the VX used for most of the coupon spiking associated with Environmental
Condition 1 was not directly confirmed because the ampoule of VX being used was
depleted before the purity sample was collected. Purity was obtained from the same
synthesis lot as the VX used for most of the spiking. Impact to the project was minimal.
The VX purity was expected to be the same because the ampoules of VX originated from
the same synthesis lot.
46
-------
• The RH levels sometimes deviated from the target RH levels during Environmental
Conditions 1 and 2. The deviations are documented in this report (see Appendix B1 and
B2) and are generally minor with regard to the magnitude of the deviation and/or the
duration of time the target RH level was not maintained. The mean RH (based on the
longest weathering periods) were within the target range of 40 ± 5% RH for
Environmental Conditions 1 and 2.
47
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5.0 Summary
The objective of this research effort was to investigate the natural attenuation of VX on various
porous or permeable materials under controlled environmental conditions. Test conditions were
consistent with an indoor environment as, for example, possible degradation by UV light was not
part of this project. Testing was conducted with unsealed concrete, plywood, rubber escalator
handrail, HDPE plastic, ceiling tile, and silanized glass (a nonporous reference material). Except
for the unsealed concrete, all materials were new and considered to be clean. Unsealed concrete
was poured in 2004. Three environmental conditions were tested with temperatures of 25 °C, 10
°C, or 35 °C, and 40% RH and one volume of chamber air exchanged per hour. Coupons of the
test materials were spiked with 2 |iL of neat VX and allowed to weather for various periods
(ranging from 30 min to 35 days). The weathered coupons were then immersed in hexane or
acetone solvent and sonicated to extract the VX. The sample extracts were quantified via GC/MS
for VX.
Natural attenuation was estimated by:
Mean VX Attenuated (%) = 100% - Mean VX Recovered (%), relative to spike controls
by material, temperature, and weathering period.
Natural attenuation measured the reduction in the amount of extractable VX remaining following
unaided degradation or volatilization of VX from the spiked materials. The VX natural
attenuation results are shown in Figure 8. The percent of VX naturally attenuated is also
presented in Table 21 by environmental condition, material, and weathering period. It is apparent
that natural attenuation of VX occurred on all six materials under all three environmental
conditions. Natural attenuation occurred fastest at warmer temperatures. For example, >90%
natural attenuation occurred with all materials tested by seven days at 35 °C, by 28 days at 25
°C, and longer than 35 days at 10 °C (i.e., 90% attenuation was not yet achieved on rubber
escalator handrail, HDPE plastic, or ceiling tile at the longest duration tested).
The time required for the natural attenuation of VX to achieve a given attenuation level was also
material-dependent. Unsealed concrete was consistently the first material to reach 90%
attenuation, followed by plywood, and then silanized glass. Longer amounts of time were
consistently required to achieve 90% natural attenuation when associated with rubber escalator
handrail, HDPE plastic, and ceiling tile.
The various mechanisms possibly contributing to the observed attenuations, such as
volatilization, chemical degradation, or inability to extract were not explicitly investigated or
quantified. However, evidence of chemical degradation was shown with the semi-quantitative
analysis of the degradation products of EMPA that were detected from plywood, HDPE plastic,
ceiling tile, and silanized glass. The detection of other toxic degradation products such as EA-
2192 was not attempted because such an analysis would require the use of liquid
chromatography/MS, which was beyond the scope of this study. Volatilization (and subsequent
reabsorption/deposition) was also likely occurring as shown with the VX detections observed
with many of the procedural blanks. In addition, relatively low VX recoveries occurred at 30 min
with unsealed concrete, indicative of extraction challenges and/or chemical degradation. The
extractability of the EMPA from any material was not investigated in this study.
48
-------
If
!
Unsealed concrete (25 °C)
— Plywood (25 °C)
Rubber escalator handrail (25 °C)
HDPE plastic (25 °C)
Ceiling tile (25 °C)
Silanized glass (25 °C)
Unsealed concrete (10 °C)
— Plywood (10 °C)
Rubber escalator handrail (10 °C)
¦ HDPE plastic (10 °C)
Ceiling tile (10 °C)
— Silanized glass (10 °C)
Unsealed concrete (35 °C)
— Plywood (35 °C)
Rubber escalator handrail (35 °C)
¦ HDPE plastic (35 °C)
Ceiling tile (35 °C)
— Silanized glass (35 °C)
8 10 12 14 16 18 20 22 24 26 28 30 32 34
Extraction Time (Weathering Period) in Days
Figure 8. Percent of VX attenuated over time by material and temperature (negative VX attenuation reflects instances when
higher VX was recovered from the test coupons than the associated spike controls).
49
-------
Table 22. Percent of VX Naturally Attenuated over Time by Environmental Condition
Material
Percent of VX Attenuation at Extraction Time (Weathering Period)*
Min
30
Hours
4 7
I
1 2 3 4 7
>ays
10
14
21
28
35
Environmental Condition 1: 25 °C, 40% RH, with One Volume of Air Exchanged per Hour
Unsealed
concrete
69
--
83
87
91
--
97
98
--
99.7
~
99.9
--
Plywood
16
--
23
38
62
--
94
98
--
99.7
~
99.9^
~
Rubber
escalator
handrail
11
--
10
44
67
--
59
68
--
81
~
91
~
HDPE
plastic
1.9
--
7.2
7.7
13
--
23
82
--
97
--
99.6
~
Ceiling tile
15
--
3.3
19
32
--
47
79
--
93
~
98
~
Silanized
glass
30
--
14
27
21
--
51
94
~
99.8
~
99.9^
--
Environmental Condition 2: 10 °C, 40% RH, with One Volume of Air Exchanged per Hour
Unsealed
concrete
44
--
57
77
--
--
86
89
--
94
97
~
96
Plywood
6.4
--
14
17
--
--
35
51
~
78
93
~
97
Rubber
escalator
handrail
0*
--
0*
0*
--
--
40
77
~
46
71
~
75
HDPE
plastic
0*
--
0*
0*
--
--
5.7
0*
~
2.9
36
--
79
Ceiling tile
0*
--
0*
0*
--
--
5.2
22
~
26
49
~
77
Silanized
glass
0*
--
0*
0*
--
--
25
44
--
62
76
~
99.7
Environmental Condition 3: 35 °C, 40% RH, with One Volume of Air Exchanged per Hour
Unsealed
concrete
69
73
81
91
96
98
--
99.8
99.7
--
--
~
--
Plywood
13
18
26
82
96
98
--
99.8
99.9^
--
--
~
~
Rubber
escalator
handrail
18
28
38
62
74
79
--
92
96
~
~
--
~
HDPE
plastic
10
4
9
20
31
74
--
99
99.7
~
~
~
--
Ceiling tile
18
13
15
43
60
78
--
97
99.1
~
~
~
~
Silanized
glass
7
11
21
67
78
91
--
99.9
99.9^
--
~
~
~
* Attenuation estimated by 100% - mean percent VX recovery relative to spike controls.
' VX was not detected from any of the replicate coupons.
i In cases where higher VX recovery occurred from the material than the spike control (i.e., the mean percent VX
recovery relative to the spike controls was >100%), a "0" was used on this table rather than presenting a negative
percent VX attenuation value.
-- = not sampled.
50
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As can be derived from Figure 8, trace amounts of VX may still be present weeks to months after
a contamination event. These amounts should be put into context with cleanup objectives and
surface concentration cleanup levels for VX which have not been established. Such cleanup
levels are expected to be site-specific and likely to be at or below the detection limit for VX (by
GC/MS) in this study. Therefore, detectable amounts of VX on these materials, even after weeks
of natural attenuation, would require decontamination/neutralization to reach the expected
cleanup level. The amount of VX observed on procedural blanks should be interpreted to
indicate that volatilization of VX results in a redistribution of some of the VX onto originally
clean surfaces; however, observed amounts were low and were also declining with time.
51
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6.0 References
EPA, 2011. Evaluation of Household or Industrial Cleaning Products for Remediation of
Chemical Agents. EPA 600/R-l 1/055. U.S. Environmental Protection Agency (EPA), Office of
Research and Development, National Homeland Security Research Center.
EPA, 2013. Stability Study for Ultra-Dilute Chemical Warfare Agent Standards. EPA 600/R-
13/044. U.S. Environmental Protection Agency (EPA), Office of Research and Development,
National Homeland Security Research Center.
EPA, 2016. Natural Attenuation of Persistent Chemical Warfare Agents on Nonporous Surfaces.
EPA 600/R-16/110. U.S. Environmental Protection Agency (EPA), Office of Research and
Development, National Homeland Security Research Center.
Groenewold, G.S., J.M. Williams, A.D. Appelhans, G.I. Gresham, J.E. Olson, M.T. Jeffery, and
B. Rowland, 2002. Hydrolysis of VX on concrete: rate of degradation by direct surface
interrogation using an ion trap secondary ion mass spectrometer. Environmental Science &
Technology 36(22):4790-4794.
Jung, H. and H.W. Lee, 2014. Understanding evaporation characteristics of a drop of distilled
sulfur mustard (HD) chemical agent from stainless steel and aluminum substrates. Journal of
Hazardous Materials 273:78-84.
Labit, H., A. Goldar, G. Guilbaud, C. Douarche, O. Hyrien, and K. Marheineke, 2008. A simple
and optimized method of producing silanized surfaces for FISH and replication mapping on
combed DNA fibers. BioTechniques 45(6):649-658.
Munro, N.B., S.S. Talmage, G.D. Griffin, L.C. Waters, A.P. Watson, J.F. King, and V.
Hauschild, 1999. The sources, fate, and toxicity of chemical warfare agent degradation products.
Environmental Health Perspectives 107(12):933-974.
Wagner, G.W., R.J. O'Connor, J.L. Edwards, and C.A.S. Brevett, 2004. Effect of drop size on
the degradation of VX in concrete. Langmuir 20(17)7146-7150.
52
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Appendix A
VX Analysis by GC/MS, Sample Chromatograms
Pile
Operatet
Acquired
I na K r^jncnt
Sample Kamo
M13 c I r* f o
Viai N'kwr.bei-
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800 (50 9UJ
Test - EPA-VX-Attenuation-5 (25°C, 40% RH)
Sample Number - AQ37841 (rubber escalator handrail coupon #5, extracted at 28 days)
Result - 4.2 pg/mL
VX and IS peaks are identified in the chromatogram
53
-------
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Test - EPA-VX-Attenuation-5 (25 °C, 40% RH)
Sample Number - AQ39181 (rubber escalator handrail coupon #5, extracted at 30 minutes)
Result - 74 (ig/mL
VX and IS peaks are identified in the chromatogram
54
-------
Appendix B
Relative Humidity during Environmental Conditions 1 and 2 testing
Figure Bl: Relative humidity during Environmental Condition 1
Additional notes: The RH briefly (approximately 5 min) dipped to 33% RH on March 31, 2016
(as measured by the Vaisala). The RH was periodically 46% on April 6 and 7, 2016 (total time at
46% RH was approximately 60 min) as measured by the HOBO located on Shelf 2, which was
associated with the 28-day samples. Only the 28-day samples were present in the chamber when
the 46% RH occurred.
Figure B2: Relative humidity during Environmental Condition 2
Additional notes: None
55
-------
50
49
48
47
• Lower Limit (35%)
Vaisala
Shelf 2 HOBO (28-day samples)
Shelf 1 HOBO (14-day samples)
Shelf 7 HOBO (7-day samples)
Shelf 6 HOBO (4-day samples)
Shelf 4 HOBO (2-day samples)
Shelf 3 HOBO (1-day samples)
Shelf 8 HOBO (7-hour samples)
Shelf 5 HOBO (30-minute samples)
33
32
31
30
Date, Time
Figure Bl. Relative humidity during Environmental Condition 1 testing (environmental conditioning was initiated on March 11,
2016; actual testing began on March 14, 2016 and continued until April 11, 2016).
56
-------
65
63
61
59
57
55
53
51
49
47
45
43
41
39
37
35
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31
29
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vvEPA
United States
Environmental Protection
Agency
PRESORTED STANDARD
POSTAGE & FEES PAID
EPA
PERMIT NO. G-35
Office of Research and Development (8101R)
Washington, DC 20460
Official Business
Penalty for Private Use
$300
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