# Presentation: 659778

## SO2 Precursor Gas Monitoring Training Overview

- Solomon Ricks, U.S. EPA, Office of Air Quality Planning and Standard, Ambient Air Monitoring Group
- Keith Kronmiller, Alion Science and Technology

## Outline

- Methodology
- Laboratory test results
- Preliminary field results
- NESCAUM Guidance Document
- Operational checks
- Instrument Operations
- Summary

## Methodology

- Why measure trace levels of SO2?
- Particulate air pollution is a complex mixture of small and large particles
- Fine sulfate aerosols form when SO2 condenses in the atmosphere

## Methodology

- What makes a high sensitivity, or “trace level,” SO2 instrument?
- Band pass filter to increase NO rejection;
- High detector sensitivity; and
- Longer optical bench.

## Methodology

**Diagram of a Precursor Gas SO****2**** Analyzer**

## Laboratory test results

| Make/Model | T-API 100AS | TEI 43C-TLE |
| --- | --- | --- |
| Averaging Time | 120 seconds | 60 seconds |
| Concentration Range | 0 – 100 ppb | 0 – 100 ppb |
| Range verified through linearity test? | Yes | Yes |
| Initial Calibration performed? | Yes | Yes |
| LDL, specified | 0.100 ppb | 0.100 ppb |
| LDL, observed | 0.653 ppb | 0.0635 ppb |
| Noise, specified | 0.200 ppb RMS – 120 sec | 0.050 ppb RMS – 60 sec |
| Noise, observed | 0.305 ppb | 0.022 ppb |
| Linearity, specified | 1% FS
m, b, and r2 reported | 1% FS
m, b, and r2 reported |
| Linearity, observed | 0.9917x + 0.1243
r2 = 0.99998 | 0.999x + 0.4449
r2 = 0.9999 |

## Laboratory Test Results

## Laboratory Test Results

## Laboratory Test Results

| Make/Model | T-API 100AS | TEI 43C-TLE |
| --- | --- | --- |
| Zero drift, specified | <0.2 ppb/day | <0.2 ppb/day |
| Zero drift, observed | 0.835 ppb (24 hr) | 0.181 ppb (24 hr) |
| Span drift, specified | <0.5%/day | 1%/day |
| Span drift, observed | 3.66% (24 hr) | 0.035% (24 hr) |
| Precision, specified | 0.5% of reading | 1% of reading |
| Precision, calculated | 1.3% | 1.3% |
| Bias, calculated | 6.26% | 11.3% |
| Response/lag time, specified | 120 sec | 110 sec (60 sec avg time) |
| Response/lag time, observed | 15 sec | 15 sec |
| Rise time, specified | 120 sec | 60 sec |
| Rise time, observed | 75 sec | 60 sec |
| Fall time, specified | 120 sec | 60 sec |
| Fall time, observed | 90 sec | 60 sec |

## Laboratory Test Results

## Laboratory Test Results

## Ambient Data ExampleJenkins Road

## Ambient Data ExampleJenkins Road

## Ambient Data ExampleJenkins Road

## Ambient Data ExampleJenkins Road

## NESCAUM Trace SO2 Monitoring Guidance for RAIN

- Provides additional operational checks for high sensitivity SO2 instruments
- Offers guidance with calibration issues
- Currently in draft form
- Last revision, March 7, 2005

## Operational checks for high sensitivity SO2 analyzers

- Is the instrument working properly?
- Response to zero air should be stable (_<_ 0.1 ppb) over intervals of 1 – 2 weeks
- Is the zero air free from contaminants?
- Use multiple sources of zero air; use the one with the lowest response
- Is data acquisition accurate at low levels?
- Digital data streams are essential for “trace” levels

## Thermo 43C-TLEDiagnostic Parameters

- DC Voltage					N/A
- PMT Voltage					N/A
- Internal Temp					8 - 47°C
- Chamber Temp					43 - 47°C
- Chamber Pressure				400 – 1000 mm Hg
- Sample Flow					0 – 1.5 LPM
- UV Lamp Intensity				10,000 – 50,000 Hz
- Lamp Voltage					500 – 1200 volts
- Optical Span Test				N/A

## Instrument Operation

**Item**						**Schedule**
- Visual inspection and cleaning                 Bi-annually
- Sample particulate filter inspection	Weekly
- Verify Test Function				Weekly
- Perform Level I calibration			Daily
- Capillary inspection and replacement 	Bi-annually
- Perform flow check				Bi-annually
- Fan filter inspection and cleaning		Bi-annually
- Lamp voltage check				Bi-annually

## Instrument Operation

| Item  | Range  | Comments |
| --- | --- | --- |
| Full Scale Range | 0 to 100 ppb | Suggested Range. |
| Units | Part per billion (ppb) | Recommended |
| Compressed Gas Cylinder | 5 – 15  ppm | NIST Traceable Protocol #1 cylinder.   |
| Calibration Ranges |  |  |
| a.  Zero | 0  ppb | There are a number of commercially available vendors. |
| b.  Level I Span | 90 ppb | NIST Traceable Protocol #1 cylinder.  Value is 90% of full scale. |
| c.  Mid Point Span | 50 ppb | NIST Traceable Protocol #1 cylinder.  Value is 50% of full scale. |
| d.  Precision Level | 20 ppb | NIST Traceable Protocol #1 cylinder.  Value is 20% of full scale. |

## Interferences

- Hydrocarbon
- 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

## Summary

- High sensitivity (trace level) instruments are commercially available for SO2
- TEI units are in production (43C-TLE)
- T-API are available for ordering with delivery date of 6/05 (100EU)
- SO2 high sensitivity instruments require few modifications
- Increased detector sensitivity and longer optical bench (TEI 43C-TLE)
- Pulsed UV fluorescence (T-API 100EU)

## Summary, cont’d

- OAQPS has compared the high sensitivity SO2 instruments against their stated performance specifications
- TEI 43C-TLE/T-API 100AS
- T-API currently developing true “trace” SO2 instrument
- Other instrument(s) are available
- Ecotech
- Has not been tested by OAQPS
- Could be tested during the field portion