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SOIL GAS SCREENING ON SOIL GAS SCREENING ON CHEMICAL WEAPONS CHEMICAL WEAPONS LEGACY SITESLEGACY SITES
Adrian Baker and Rebecca LeeAdrian Baker and Rebecca Lee
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
CONTENTS….CONTENTS….
Objectives of the research
Concept development
Phase 1: range trial
Phase 2: field trial
Phase 3: site survey
Future work
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
OBJECTIVES OF THE RESEARCHOBJECTIVES OF THE RESEARCH
To develop a rapid, discrete and non-intrusive sampling method for assessing and characterising sites potentially contaminated with mustard agent
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
CONCEPT DEVELOPMENTCONCEPT DEVELOPMENT
Volatile compounds: 1,4-dithiane, 1,4-thioxane, chlorobenzene
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
PROBE DESIGNPROBE DESIGN
Three stainless steel probes were designed and constructed
They worked on a lost point principal
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
EQUIPMENTEQUIPMENT
RaidM-100 AP2CCAM
TDTPump1L Syringe
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
PHASE 1 PHASE 1 –– RANGE TRIALRANGE TRIAL
Spiked sand samples with signature compounds
50 kg dry sand and 2 L water mixed in drum
Add 1mg, 10mg, 100mg, 1g, 10g in 1kg sand of:
- Chlorobenzene
- 1,4-dithiane
- 1,4-thioxane
Gives concentrations of:
- 0.02, 0.21, 2.1, 21 and 210 mg/kg
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
Set up drum in cement mixerSet up drum in cement mixer
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
Insert soil gas probeInsert soil gas probe
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
Extract gas with syringe and pass through Extract gas with syringe and pass through AP2C and RAIDAP2C and RAID--MM
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
Take a thermal desorption tube sample Take a thermal desorption tube sample for laboratory analysisfor laboratory analysis
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
RANGE TRIAL RESULTSRANGE TRIAL RESULTS
RaidM-100 – poor results, not specific enough
AP2C – identified dithiane and thioxane at ~100 µg/m3
GCMS analysis – identified:- Chlorobenzene to <100 µg/m3
(lowest concentration used)
- Dithiane to ~40 µg/m3
- Thioxane to ~6 µg/m3
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
PHASE 2 PHASE 2 –– FIELD TRIALFIELD TRIAL
Aim: to collect soil gas from some areas known to be contaminated and some areas not thought to be contaminated
Suspected mustard burning pits located in Area 10A
Set of samples taken along 30m transect line adjacent to one burning pit
Set of samples taken from burning pits themselves
Temperature during trial 2-3°C
BURN PIT
VAPOUR CORE SAMPLING SEPT 2005
SOIL GAS SAMPLING ALONG 30m TRANSECT
VAPOUR SAMPLING SEPT 2005
SOIL GAS SAMPLING IN BURN PITS
AREA 10A
V/C
V
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
Insert soil gas probeInsert soil gas probe
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
Extract gas from the soilExtract gas from the soil
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
Pass soil gas through the detector (AP2C) to identify sulphur compounds (contained in a number of mustard breakdown products)Pass soil gas through the detector (AP2C) to identify sulphur compounds (contained in a number of mustard breakdown products)
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
Extract soil gas through a thermal desorption tube for subsequent analysis in the lab
Extract soil gas through a thermal desorption tube for subsequent analysis in the lab
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
FIELD TRIAL RESULTSFIELD TRIAL RESULTSTransect
– Some chlorobenzene, dithiane and thioxaneidentified (GCMS)
– But coincident with probe number indicating cross contamination
– Low levels of thioxane at 2 locations (GCMS)– Not coincident with probe, real contamination– Nothing identified on AP2C
Burning Pits– 4-5 bars on AP2C, 0 bars on CAM– High concentrations of chlorobenzene (300-
500 µg/m3), dithiane (>2000 µg/m3), thioxane (80-650 µg/m3)
– Low (but detectable) concentrations of mustard (<40 µg/m3)
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
FIELD TRIAL SUMMARYFIELD TRIAL SUMMARY
Soil gas sampling approach works
Evenly mixed dithiane or thioxane detectable to:
- 0.02 mg/m3 in soil by GCMS
- 2.1 mg/m3 in soil by AP2C
Field trial clearly identified burning pit
- and detected mustard even though the temperature was below its freezing point
But, cross contamination issues were encountered
Need for disposable soil gas sampling tubes (i.e. kit redesign)
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
EQUIPMENT MODIFICATIONEQUIPMENT MODIFICATION
Equipment redesigned to avoid cross contamination issue and to be more user friendly
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
PHASE 3 PHASE 3 –– SITE SURVEYSITE SURVEY
Ex RAF siteStored chemical weapons during WWIIRequired site survey (trial pits and sampling) prior to redevelopmentSoil gas survey carried out at each trial pit location to support the site investigation work and to field test new equipment
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
SITE SURVEY RESULTSSITE SURVEY RESULTS
No chlorobenzene, thioxane, dithiane or mustard detected at any location (AP2C or GCMS)
Results matched with soil samples taken from trial pits
Serious problem with waterlogging
Unable to extract soil gas at many locations
Extracted water on some occasions
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
FUTURE WORKFUTURE WORK
Continued development of the approach and undertaking of a full survey on a site known to be contaminated
Plan to use this as the first stage in the assessment of any potential CW legacy sites in the UK to help to inform risk assessments and to locate intrusive investigations
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
CONCLUSIONSCONCLUSIONS
Soil gas sampling approach does appear to be a viable method for screening mustard contaminated sites
There are a number of limitations on its use
Some more development is needed, including a full proof of principal study in the field
© Dstl 200723 May 2007 Dstl is part of the
Ministry of Defence
ANY QUESTIONS?ANY QUESTIONS?