tracer dispersion studies1 tracer release experiments damien martin, catheryn price, tony makepeace,...

Tracer Dispersion Studies 1

Tracer release experimentsTracer release experiments

Damien Martin, Catheryn Price, Tony Makepeace, Graham Nickless, Peter Simmonds, Brian Greally, Alan Knights, Simon O’Doherty and Dudley Shallcross,

Rex Britter and Marina Neophytou.

University of Bristol and University of Cambridge

Tracer Dispersion Studies2

OutlineOutline

Tracer methodology – brief reviewFirst results from DAPPLE IOn-going developmentsThoughts on DAPPLE IIAcknowledgements


Tracer properties required Tracer properties required

Non-toxic Inert (long lifetime)Non-depositingLow background concentrationSensitive detection method

Answer: Perfluorocarbon tracers (SF6)


PerfluorocarbonsPerfluorocarbons

Typical background concentrations ppq Can be separated from air sample using

Gas Chromatography and detected using negative ion chemical ionisation (NICI) mass spectrometry

Perfluoromethylcyclohexane (PMCH) Perfluoromethylcyclopentane (PMCP)


The ApparatusThe Apparatus

GC-MS systemTracer release equipment (cylinders)Sampling system


Schematic of GC-MS systemSchematic of GC-MS system

NICI-MSADS GC

Air sample

PC


Separation of PDMCH isomersSeparation of PDMCH isomersCarbograph PLOT Column

NOTE:

• PMCP

(methyl cyclopentane)

• PMCH

(methyl cyclohexane)

•o c PDCH

(ortho cis dimethyl cyclo hexane)


Automated Bag SamplersAutomated Bag SamplersBattery Operated Bag Sampler

•Internal pump to air intake

•Controller is chip based, this automates sample sequence : Internal clock to control times

•Solenoid controller flow block determines which bag is filled

•Tedlar bags attach to Teflon tubing - 3L air target for background concentration

•Sampling time determined by volume of Tedlar bag (to 5L) and release rate of tracer.


Protocol for releaseProtocol for release

Tracers sealed in cylinders and transported to site.

Release apparatus set up 1 hour before expt. to allow system to stabilise.

All tubing is flushed prior to arrival at site. Weight loss of all tracers and pressure drop on

all cylinders monitored throughout the expt. Entire release system is sealed and all samplers

collected and closed and transported off site, then release system removed to avoid accidental post-release.


Release regimeRelease regime

Release both PMCH and SF6 from same site in York Street (see later)

Release PMCH for 15 mins.Release SF6 for 15 mins. but offset

by 1.5 mins, i.e. SF6 release starts after PMCH.


Problems to overcome Problems to overcome

Iraq war, security, releasing chemicals in London !

Safety of personnel and equipment during experiment.

Access to suitable release sites.A major achievement under these

circumstances.

12Tracer Dispersion Studies

York Street

Library

Bickenhall Street

WestminsterCouncil House

Gloucester Place

Thornton Place

Bickenhall Mansions

Baker Street

Marylebone Road

x

X = tracer release site

1

3 2

6 7

8

5

4

9

10


Results from DAPPLE I 15/5/03Results from DAPPLE I 15/5/03

PMCH concentration for integrated 3 minute samples

0

500

1000

1500

2000

0 2 4 6 8 10

Integrated 3 minute sample, no.

PMCH

concentration (ppqv)

Wesrminister - Ground level

Westminister - Roof level

Bickenhall mansions

End of York Street

Thornton Place


Results from DAPPLE I 15/5/03Results from DAPPLE I 15/5/03

PMCH and SF6 concentrations measured at roof site

0

200

400

600

800

1000

0 2 4 6 8 10

Integrated 3 minute sample, no.

PMCH

concentration

(ppqv)

0100

200300400500

600

SF6

concentration

(pptv)

PMCH

SF6


On-going developmentsOn-going developments

Rest of analysis to be completed by mid August.

Developing capability to release 3 PFC tracers (PMCH, PMCP, o c DMPCH) separately.

Developing a ‘real-time’ analyser for PFCs (1 minute sampling) and same for SF6

Hope to be able to release 3 tracers in 3 locations simultaneously and to have 1 real-time analyser available for DAPPLE II.


Thoughts on DAPPLE IIThoughts on DAPPLE II

Propose to plan for three different release experiments, with location of samplers and release sites to be discussed with Rex in September.

We should then be able to take advantage of any (most) wind directions.

Use of several tracers should be extremely illuminating, where several problems can be tackled simultaneously. Real-time data will we hope also provide useful information.


ConclusionsConclusions

First release was a success, amount released was about right, i.e. did not overload the analysers and was not too small.

Already some interesting observations, no tracer at the end of York Street, similar levels at roof and ground level of W.C.C.


AcknowledgementsAcknowledgements

EPSRC – DAPPLE MSG – MODNERC - studentship


Adsorbent-filled Macrotrap SamplersAdsorbent-filled Macrotrap Samplers

Automated Macrotrap sampler

•Internal processor controlled

•Programmed to sample 3 litres of air onto macrotraps followed by isolation of the trap until lab analysis possible

•15 traps per box - up to 5 hours sampling time

•Macrotraps undergo thermal desorption into ADS system in central laboratory


Release monitoring (pressure)Release monitoring (pressure)

PMCH RELEASE PRESSURE DROP

3

3.1

3.2

3.3

3.4

3.5

16:19:12 16:33:36 16:48:00 17:02:24 17:16:48 17:31:12 17:45:36

TIME

PRESSURE (BAR)

tracer dispersion studies1 tracer release experiments damien martin, catheryn price, tony makepeace,...

Documents

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release apparatus

entire release system

suitable release sites

accidental postrelease

laterrelease pmch