1. SO2 Precursor Gas Monitoring Training Overview
Lewis Weinstock
Solomon Ricks, U.S. EPA
Office of Air Quality Planning and Standards

2. Outline Methodology Field test results Responses to Calibrations
Burden’s Creek SO2 Frequency Distribution
Instrument Operations
Summary

3. 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 studies
Need highly-sensitive ambient monitors deployed around these areas to determine CAIR’s effect on SO2 and related species.

4. 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

5. Methodology (UV Light Path)
SO2 + hv214nm SO2*
SO2* SO2 + hv330nm

6. Methodology (General Schematic)
General Diagram of a Precursor Gas SO2 Analyzer

7. Currently Available Trace-Level SO2 Options
Teledyne-API 100EU
EQSA
Thermo Electron 43C-TLE
EQSA
(new model: 43i-TLE)
Ecotech EC9850T
EQSA

8. Testing Results – Field April 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 =
MDL Observed
0.055 ppb (0.038 – ppb CL)

10. Recertified Environics calibrator

11. Recertified Environics calibrator?

12. Burdens Creek – Ambient Concentrations
Span Level
Precision Level

13. Burdens Creek – Ambient Concentrations

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

15. 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
Fan filter inspection and cleaning
6 months depending on surroundings
Lamp voltage check
When lamp voltage approaches maximum (1200v)

16. Hydrocarbons Nitrogen oxide Interferences
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

17. SO2 Response due to NO interference