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?