EPA Precursor Gas Training Workshop

SO2 Precursor Gas Monitoring Training Overview

Lewis Weinstock

Solomon Ricks, U.S. EPA

Office of Air Quality Planning and Standards

EPA Precursor Gas Training Workshop

Outline

• Methodology• Field test results• Responses to Calibrations

• Burden’s Creek SO2 Frequency Distribution

• Instrument Operations• Summary

EPA Precursor Gas Training Workshop

Why measure trace levels of SO2

Objectives:• Emission strategy

development• Effectiveness of

reduction strategies• Validation of SO2 and

sulfate modeling predictions

• Long term trends analysis

• Health effect studiesNeed highly-sensitive ambient monitors deployed around these areas to determine CAIR’s effect on SO2 and related species.

EPA Precursor Gas Training Workshop

Trace Level Sampling Challenges (SO2)

• Performance challenges– Lower noise for reduced LDL/MDL– Reduced zero and span drift– Increased rejection of interferences

• Trace level modifications– Special band-pass filter to increase NO rejection– Improved light baffling to reduce stray light– More powerful UV source lamp– Higher detector sensitivity– Longer optical bench

EPA Precursor Gas Training Workshop

Methodology (UV Light Path)

SO2 + hv214nm SO2*

SO2* SO2 + hv330nm

EPA Precursor Gas Training Workshop

Methodology (General Schematic)

General Diagram of a Precursor Gas SO2 Analyzer

EPA Precursor Gas Training Workshop

Currently Available Trace-Level SO2 Options

Teledyne-API 100EUEQSA-0495-100

Ecotech EC9850TEQSA-0193-092

Thermo Electron 43C-TLEEQSA-0486-060(new model: 43i-TLE)

EPA Precursor Gas Training Workshop

Testing Results – FieldApril 2006

Make/Model Thermo 43C-TLE (observed)

Averaging Time 60 seconds

Conc. Range 0-100 ppb

Zero Drift (0.200 ppb/day) 12 hr. (0.199 ppb)24 hr. (0.200 ppb)

Span Drift (1% FS per week) 20% FS (0.06%)80% FS (0.27%)

Precision (Coefficient of Variance)

0.91%

Bias +1.08%

LDL (0.100 ppb) 0.112 ppb

Noise (0.050 ppb) 0.029 ppb

Linearity (1% FS. M, B, and R2 reported)

1.0163x-0.454

R2 = 0.9995

MDL Observed 0.055 ppb (0.038 – 0.148 ppb CL)

EPA Precursor Gas Training Workshop

SO2 TEI - Zero Drift - Burdens Creek

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

EPA Precursor Gas Training Workshop

SO2 TEI - Span Drift at 90 ppb - Burdens Creek

-20.0%

-15.0%

-10.0%

-5.0%

0.0%

5.0%

10.0%

15.0%

20.0%

Recertified Environics calibrator

EPA Precursor Gas Training Workshop

SO2 TEI - Precision Drift at 10 ppb - Burdens Creek

-20.0%

-15.0%

-10.0%

-5.0%

0.0%

5.0%

10.0%

15.0%

20.0%

Recertified Environics calibrator

?

EPA Precursor Gas Training Workshop

Burdens Creek – Ambient Concentrations

Precision Level

Span Level

EPA Precursor Gas Training Workshop

Burdens Creek – Ambient Concentrations

Burdens Creek Frequency Distribution - SO2

-2

0

2

4

6

8

10

12

99 90 75 50 25 10 1

Percentile

pp

b

EPA Precursor Gas Training Workshop

Thermo 43C-TLE Diagnostic Parameters (5-11-07)

TEI Diagnostics Actual Reading Acceptance Criteria Acceptable?

Range 100 0 - 100 ppb Y

Averaging Time 60 10 – 300 seconds Y

SO2 Background 3.36 0 – 10 ppb Y

SO2 Span Coefficient 1.030 0.800 – 1.200 Y

PMT Voltage -604 ~ -600 V Y

Lamp Voltage 1211 500 - 1200 V N

Power (+5/+15/-15/Battery) 4.9/14.9/-14.9/3.4 + 0. 1V, >3.0 V Y

Internal temperature 36.8 8 – 47 degC Y

Chamber Temperature 45.2 43 – 47 degC Y

Chamber Pressure 729.5 650 – 760 mmHg Y

Sample Flow 0.587 0.5-1.0 l/min Y

UV Lamp Intensity 13,947 10,000 – 50,000 Hz Y

Change Particle Filter Y N Respan 89.8 PPB

EPA Precursor Gas Training Workshop

Instrument Operation

Item Schedule

Check diagnostics (if not available remotely) Bi-weekly

Visual inspection and cleaning 6 months

Replace sample particulate filter Bi-weekly to monthly based on PM levels

Perform QC gas challenge (Level 1 and precision)

Bi-weekly (daily recommended)

Capillary inspection and replacement 6 months

Fan filter inspection and cleaning 6 months depending on surroundings

Lamp voltage check When lamp voltage approaches maximum (1200v)

EPA Precursor Gas Training Workshop

Interferences

•Hydrocarbons

•Fluoresces in a fashion similar to SO2 when exposed to UV light

•Removed through the hydrocarbon “kicker”

•Nitrogen oxide

•NO fluoresces in a spectral range close to SO2

•Band pass filter enhances NO rejection

EPA Precursor Gas Training Workshop

NO Rejection Test

0

20

40

60

80

100

120

NO

Con

cent

ratio

n, p

pb

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

SO2

Con

cent

ratio

n, p

pb

NO SO2

SO2 Response due to NO interference