Trace Gas Dispersion Analysis

Gaussian Plume Model of PFT Distribution

SAS 60 14 m N of Center

0

100

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2:00 2:14 2:28 2:43 2:57

Time of Day

fL/L

PDCB

PMCP

PMCH

ocPDCH

iPPCH

PTCH

Tracer Release Stop

SAS 90 Center

0

100

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2:00 2:14 2:28 2:43 2:57

Time of Day

fL/L

PDCB

PMCP

PMCH

ocPDCH

iPPCH

PTCH

Tracer Release Stop

SAS 80 44 m S of Center

0

100

200

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2:00 2:14 2:28 2:43 2:57

Time of Day

fL/L

PDCB

PMCP

PMCH

ocPDCH

iPPCH

PTCH

Tracer Release Stop

PMCH

i-PPCH

PTCH

PMCP

o-PDCH

PDCB

Perflurocarbon Tracers (PFTs) have been in use since the late 70s and

early 80s. They have been used for various reasons in different

commercial enterprises, building ventilation measurements, petroleum

reservoir (gas and oil) studies for enhancing recovery from reserves, and

underground cable leak hunting for the utility industry. 1

The focus of the experiment with PFTs is to determine if the variation in

approximately one to five meter distances, in the source location, affects

the dispersion pattern for different tracers. This would help cut costs

during any of the before mentioned commercial uses of the PFTs, and

help to show how close multiple release points can be to be considered

the same release point. Looking at the dispersion pattern could also help

with mapping out where a gas would go if a toxic gas were to be

dispersed in an urban area.2

Introduction

The Gaussian Dispersion Model was used to predict the probable outcome of

the experiment. The equation was set up with the idea of having the height be

at zero.

Through this we got the values that had concentrations in fL/L (ppqv). We

then mapped out the field according to how the dispersion model looked. The

six tracers used for the experiment were PMCP, oPDCH, PDCB, iPPCH,

PTCH, and PMCH. The PTCH and PMCP were released together to serve as

the control. The tracers were released through syringe pumps that were

placed adjacently in four different locations from the co-released PFTs. The

syringes were filled with an approximate dilution of twenty to one methanol to

PFT solution. For the first test the seven Serial Atmospheric Sampler (SAS)

units were placed somewhere near the 200 meter mark of the dispersion

model, at 25 meter increments from the centerline in five different positions.

One SAS at each outlying position of 50 meters from centerline, two at each

25 meter setting from centerline, and two on the centerline. Within each SAS

unit were ten Capillary Adsorbent Tracer (CAT) tubes each taking six minute

samples of the air. The second test had the most of the same setup only with

the SAS units being placed closer together and at seven different positions,

also the CAT tube sampling time was increased from six minutes to twelve

minutes with only six CAT tubes sampling. After both of the tests we took the

ten, or in the case of the second test six, CAT tubes from each of the SAS

units to be loaded into the GC for the air sampling analysis. The GC ran the

CATs through in 15 minute increments.

Methods

After the GC analyzed the samples, the chromatographs showed the peak

heights in V which we then converted using calibration curves generated

from mixed PFT standards to femtoliters per liter. The charts showed a

general corresponding ratio to each other that most of the PFTs followed

throughout the test, mainly in the higher concentration zones of the

results. Half of the PTFs showed concentrations comparable to the

concentrations predicted in the Gaussian Distribution Model.

Results

2

20

)0,,( )(2

)(exp

yzy

yx x

yy

uxx

QX

XAVIER DRIVERTHOMAS A. ABERICHARD DEANE

Fort Berthold Community CollegeNew Town, ND 58763.

X = [PFT] @ p& y (at same height as release), position x pL/m^3(=ppqv)Q = The PFT release rate, fL/sσ(x)z = Vertical plume std dev: = b*x^n, mσ(x)y = Crosswind plume std dev: = a*x^m, m

ū = the mean wind speed, m/s

x = the downwind distance, m

JOHN HEISERRUSSELL DIETZRICHARD WILKE

THOMAS B. WATSONGABRIEL VIGNATO

Brookhaven National LabsUpton, NY 11973

PFTs showing up as global background 1

Perflurocarbon Tracers (PFT)

PFTs from Ball Field test indicating high PFT concentrations

Varian Electron Capture GC

Chemical structure of PTCH a PFT

Brookhaven summer PFT release area 2008

PTCH

Charts indicate the relative concentrations of PFTs are proportional to each other as detected from samplers below

Tentative conclusions indicate that since the sampled concentrations of

PFTs maintain similar relative concentration to each other regardless of

sampling unit, then this is a characteristic of co-released samples. This

is only one indication which will be followed by more detail comparisons

of PFT to PFT ratios. There is also a concern that the samples were

not diluted to the desired 20 to 1 dilution due to immiscibility or PFT

volatility of each PFT at that dilution in methanol.

ConclusionsA special thanks to the follow in related and coordinating programs:

1 The Staff at Office of Educational Programs (OEP) at Brookhaven

National Lab for their innovative and continuous support

2 The NSF Fast Staff for designing and implementing this program

3 The Department of Energy (DOE) for working with BNL on the project

4 Fort Berthold Community College and The Mandan Hidatsa and Arikara

Tribal affiliates for coordinating with the above programs

Acknowledgements References 1 Dietz, R. N. and Goodrich, R. W. “Measurement of HVAC  system performance and local

ventilation using passive perfluorocarbon tracer technology”. Prepared in part for the State

University of New York, College of Technology, Farmingdale, NY. Informal Report,

BNL-61990, June 1995 2 Thomas B. Watson, John Heiser, Paul Kalb, Russell N. Dietz, Richard Wilke, Robert Wieser, and Gabe Vignato, “ NEW YORK CITY URBAN DISPERSION PROGRAM MARCH 2005 FIELD STUDY: TRACER METHODS AND RESULTS”, Brookhaven National Laboratory,Environmental Sciences Department June 2006

3 Thomas B. Watson, Richard Wilke, Russell N. Dietz, John Hieser, and Paul

Kalb,”Atmospheric Background Perfluorocarbons Used As Tracers” , Supplimental

Information, Brookhaven National Laboratory, Upton, New York, 11973