Vermont Benzene MonitoringRFA OAR-EMAD-05-18 • Grant Study Objectives – To assess spatial and...

SemiSemi--continuouscontinuous Benzene Monitoring Benzene Monitoring in Burlington, Vermontin Burlington, Vermont

Robert C. LacailladeVermont Department of Environmental Conservation

National Air Monitoring Conference November, 2009

November, 2009 Vermont DEC 2

Background

• Vermont DEC Awarded EPA Grant in 2006 – Local-Scale Air Toxics Ambient Monitoring Program Grant

RFA OAR-EMAD-05-18

• Grant Study Objectives– To assess spatial and temporal characteristics of benzene

in Burlington, Vermont– Evaluate and validate a benzene dispersion model

• Short-term Benzene Concentrations Beneficial– Semi-continuous analyzer viable alternative to

canisters/tubes


Overview

• Design Specs• Installation• Calibration• Data Handling, Validation & Reporting• Quality Assurance• Summary of 1-Hour Benzene Results• Comparisons to TO-15 (24hr & 6hr canisters)• Summary & Observations


“Syntec Spectras GC955 Series 600 BTEX Analyzer”• Designed to measure “BTEX” compounds in air

– benzene, toluene, ethylbenzene and xylenes

• Computer Controlled Gas Chromatograph-PID – Embedded-PC running proprietary software– Windows XP, 40 Gigabyte HD, PC-Anywhere – 19” Standard Instrument Rack Mount– 10” integrated monitor, External keyboard & mouse

• Manufactured by Synspec (The Netherlands)– U.S. Distributor: Wilbur Technical Services, LLC


Design Specifications• Carrier gas- N2 (Ultra High Purity)

• Preconcentrator- Tenax GR• Column: 15 m x 0.32mm (ID)

– 95% dimethylpolysiloxane; 5% diphenylpolysiloxane

– 2-meter “stripper” column – 13-meter “analysis” column

• PID- 10.6 eV, 50 µl measurement cell• 15-minute analysis run time

per Sample• “Semi-continuous”; allows for

simultaneous collection of next air sample while previous sample is analyzed

• Design keys– 10-port valve– Preconcentrator– Precision sampling piston


Installation

• Burlington Monitoring Shelter – In downtown city parking lot on corner of 2 busy streets– Across street from a gas station and newspaper

publisher, next door to fire station

• Connected to Common Glass Sample Manifold – 1/8” Silco-coated stainless tubing– 2µ sintered-stainless particulate inlet filter

• Internet Connection via Dedicated DSL Line – Allows offsite communication, data review/download– Remote control via PC-Anywhere


Calibration Equipment• Software Calibration “mode”

– Linear /non-linear– optional “auto-linearization” function – Retention times verified/edited

• BTEX Calibration Gas – Spectra or Scott– 0.6 or 1 ppmv – 5% analytical accuracy w/ 1-yr cert.

• Zero Air– TEI Model 111

• Dilution Calibrator– Environics Model 6103

• 0-10 sccm gas MFC• 0-20 lpm Air MFC


Synspec Benzene Calibration

Synspec GC955Two-Tiered Calibration Approach for Benzene:Transition from Primary Range to High Range

0

1

2

3

4

5

6

7

0 100000 200000 300000 400000 500000 600000 700000 800000 900000 1000000

PID Response

Con

c. (p

pbv)

Primary Range (0-2 ppbv) High Range (2-5 ppbv)

• Six-point Calibration – Input Levels: 0.07, 0.2, 0.5, 1, 2, 4 ppbv• Two-tiered Approach

– Primary Range 0-2 ppbv (98% of measured values)– High Range 2-5 ppbv

• Non-linear Regression (software auto-linearization not utilized)– R2=0.9994– Method detection limit =0.04 ppb (y-intercept)[0-2 ppbv Calibration] [2-5 ppbv Calibration Transition]


Data Handling

• Chromatograms – Each 15-min sample analysis run is saved to a separate

binary file – Files can be viewed on analyzer or desktop (running Synspec

program) for review and validation

• Output File of Results– Results of each analysis written to a text file (PID response,

ppbv, retention time, operating parameters)– Text file is retrieved using PC-Anywhere and imported to

EXCEL and ACCESS for review and validation – 15-min values used to generate 1-hour averages

• 75% data averaging rule (minimum of 3, 15-min values for 1-hr avg.)


Data Validation• Performance Audits

• Review Text File With Excel/Access – Missing/suspect values– Retention time/operating

parameter verification– Flagging/validation

• Review Chromatograms of Selected Runs– Verify retention time,

peak area, identification, concentration


Data Validation (continued) & Reporting

• Visually Review Results Graphically

– Time series, fingerprint plots

– Scatter plot of benzene/toluene ratios for review of suspect values

• Valid 15-minute Results Reported to AQS

Synspec GC955 Benzene vs. Toluene 1-hour Avg. (ppbv) July 2007- June 2008

0

2

4

6

8

10

12

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50

Benzene Concentration (ppbv)

Tolu

ene

Con

cent

ratio

n (p

pbv)

BTEX Retention Times July 2008

152

154

156

158

160

162

164

166

168

170

172

date time

Benz RT


Quality Assurance

• QAPP approved by EPA-New England

• Routine performance audit – MQO +/-15% Difference

• Biannual independent accuracy audit – “second source” gas standard– Independent dilution calibrator, zero air system – MQO +/-20% Difference

• Data capture– Quarterly DQO: 75%


Synspec GC955 Performance Audit Responses for Benzene at Various Inputs Levels (ppbv)

July 2007 - June 2009

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

2.50

6/27

/07

7/27

/07

8/27

/07

9/27

/07

10/2

7/07

11/2

7/07

12/2

7/07

1/27

/08

2/27

/08

3/27

/08

4/27

/08

5/27

/08

6/27

/08

7/27

/08

8/27

/08

9/27

/08

10/2

7/08

11/2

7/08

12/2

7/08

1/27

/09

2/27

/09

3/27

/09

4/27

/09

5/27

/09

6/27

/09

Ben

zene

(ppb

v)

0.26 0.52 1.05

2.04 2.1 2.12

ppbv input level


CV= 5.2% (Based on Equation 2 from 40CFRPart58, App.A)

Synspec GC955 Performance Audit Results for Benzene at Various Input Levels (% Difference)

July 2007 - June 2009

-25

-20

-15

-10

-5

0

5

10

15

20

256/

27/0

7

7/27

/07

8/27

/07

9/27

/07

10/2

7/07

11/2

7/07

12/2

7/07

1/27

/08

2/27

/08

3/27

/08

4/27

/08

5/27

/08

6/27

/08

7/27

/08

8/27

/08

9/27

/08

10/2

7/08

11/2

7/08

12/2

7/08

1/27

/09

2/27

/09

3/27

/09

4/27

/09

5/27

/09

6/27

/09

% D

iffer

ence

0.25 0.5 0.75 1 2

ppbv input level

MQO +/- 15%


Synspec GC955 Independent Accuracy Audit Results

for BenzeneInput (ppbv)

Response (ppbv)

% Diff.

8/31/07 2.71 3.01 11.1

4/24/08 3.00 3.01 0.3

8/3/08 2.02 2.00 -1.0

5/12/09 1.080.54

1.010.50

-6.5-7.4


Benzene 1-Hour Averages for Local Scale Grant Study Period

Based on 15-minute values; 94% Valid Data Capture

Synspec GC955 Benzene 1‐Hour Average Concentrations (ppbv) Burlington, July 2007 ‐ June 2008

0.0

0.5

1.0

1.5

2.0

2.5

7/1/07

7/11

/07

7/22

/07

8/2/07

8/13

/07

8/24

/07

9/4/07

9/15

/07

9/26

/07

10/6/07

10/17/07

10/28/07

11/8/07

11/19/07

11/30/07

12/11/07

12/22/07

1/1/08

1/12

/08

1/23

/08

2/3/08

2/14

/08

2/25

/08

3/7/08

3/18

/08

3/28

/08

4/8/08

4/19

/08

4/30

/08

5/11

/08

5/22

/08

6/2/08

6/13

/08

6/23

/08

Date

Concen

tration (ppb

v)

Confirmed gas station delivery ~50-70m from trailer 8/29/2007

Confirmed gasoline spill near trailer 4/18/2008

Burlington GC955 Benzene 15-minute Average Concentration (ppbv)

4/18/08, 12:00-14:00 Hours

0

1

2

3

4

5

6

12:00 12:15 12:30 12:45 13:00 13:15 13:30 13:45 14:00

Benz

ene

Conc

. (pp

bv)


Comparison of Synspec GC955 to TO-15 CanistersBenzene and Toluene 24-hour Averages Collocated (1/12th day)

at Burlington,Vermont July 2007-January 2009

00.20.40.60.8

11.21.41.61.8

2

6/23

/07

7/5/

077/

17/0

77/

29/0

78/

10/0

78/

22/0

79/

3/07

9/15

/07

9/27

/07

10/9

/07

10/2

1/07

11/2

/07

11/1

4/07

11/2

6/07

12/8

/07

12/2

0/07

1/1/

081/

13/0

81/

25/0

82/

6/08

2/18

/08

3/1/

083/

13/0

83/

25/0

84/

6/08

4/18

/08

4/30

/08

5/12

/08

5/24

/08

6/5/

086/

17/0

86/

29/0

87/

11/0

87/

23/0

88/

4/08

8/16

/08

8/28

/08

9/9/

089/

21/0

810

/3/0

810

/15/

0810

/27/

0811

/8/0

811

/20/

0812

/2/0

812

/14/

0812

/26/

081/

7/09

1/19

/09

1/31

/09

Date

ppbv

Benzene TO-15 (6L-canister, 24-hr sample) Toluene TO-15 (6L-canister, 24-hr sample)Benzene TO-15 Duplicate (6L-canister, 24-hr sample) Toluene TO-15 Duplicate (6L canister, 24-hr sample)Synspec Benzene (24-hour avg. of 15-min values) Synspec Toluene (24-hour avg. of 15-min values)

Synspec 24-hr averages based on average of 96 separate 15-minute values for each 1/12th-day run day; TO-15 results based on individual GC/MS analysis of 24-hour canister sample


Mean Absolute Difference= -0.05 ppbvCV=17% (Based on NATTS Equation 2.1.2)

Comparison of Synspec GC955 Benzene Results to TO-15 CanistersRelative % Difference & Absolute Difference of ppbv 24-hour Averages Collocated (1/12th day) at Burlington Site

July-2007 thru January-2009

-50

-40

-30

-20

-10

0

10

20

30

40

506/

23/0

77/

5/07

7/17

/07

7/29

/07

8/10

/07

8/22

/07

9/3/

079/

15/0

79/

27/0

710

/9/0

710

/21/

0711

/2/0

711

/14/

0711

/26/

0712

/8/0

712

/20/

071/

1/08

1/13

/08

1/25

/08

2/6/

082/

18/0

83/

1/08

3/13

/08

3/25

/08

4/6/

084/

18/0

84/

30/0

85/

12/0

85/

24/0

86/

5/08

6/17

/08

6/29

/08

7/11

/08

7/23

/08

8/4/

088/

16/0

88/

28/0

89/

9/08

9/21

/08

10/3

/08

10/1

5/08

10/2

7/08

11/8

/08

11/2

0/08

12/2

/08

12/1

4/08

12/2

6/08

1/7/

091/

19/0

91/

31/0

9

Rel

ativ

e %

Diff

eren

ce

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

Abs

olut

e D

iffer

ence

of p

pbv

Benzene %RPD Benzene Absolute Difference of ppbv

TO-15 MOQ for Collocated Samples=30%


Synspec GC955 Compared to TO-15 Canisters (Continued)

Comparison of Synspec GC955 and TO-15 Canisters Benzene 24-hour Averages (ppbv)

July 2007- January 2009 (n=46)

y = 1.27xR2 = 0.92

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70

Synspec 24-hour Average (ppbv)

TO-1

5 24

-hou

r Can

iste

r (pp

bv)

1:1

Comparison of Synspec GC955 and TO-15 Canisters Benzene 6-hour Averages (ppbv)

Four Separate 1-week Periods 2007-2008 (n=108)

y = 1.29xR2 = 0.93

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.00 0.20 0.40 0.60 0.80 1.00 1.20

Synspec 6-hour Average (ppbv)TO

-15

6-hr

Can

iste

r (pp

bv)

1:1


Summary & Observations• Synspec is an Enhancement to Air Toxics Monitoring program

– Well designed and reliable– Consumables & maintenance reasonable– Provides real-time, short-term benzene concentrations– Analytical precision, accuracy and sensitivity comparable to TO-15– Collocated results compare well with TO-15 & NATTS performance-

based criteria

• Performance & Data Quality/Learning Curve– Requires time for analyzer and software familiarity – Trace level dilution calibrator improves low-level performance – Data review/validation more time intensive compared to “criteria”

analyzers

• Further Development & Study – Continue to improve low-end sensitivity and accuracy – Evaluate implementation of “auto-linearization” program function – Streamline data management, review and validation techniques


Acknowledgements

• Jenny Berschling, Project Lead, VTDEC• John Simone, QA Analyst-VTDEC• Heidi Hales, Air Toxics Coordinator- VTDEC• Vermont DEC Organics Lab • Tracey Footer, ERG (formerly VTDEC)• John Wilbur, Wilbur Technical Services• Michael Rijpkema, Synspec• Wouter Lautenbach, Synspec


Thank you, Opryland!

• Robert C. Lacaillade, Vermont DEC• (802) 241-3852 • [email protected]

mailto:[email protected]

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Vermont Benzene MonitoringRFA OAR-EMAD-05-18 • Grant Study Objectives – To assess spatial and...

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