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April 7: QA Systems, EPA definitions, PQAOs and common sense – Mike Papp

April 14: Routine Quality Control and Data Management (1-pt QC, flow rate, and instrument stability checks) – Travis Maki

April 21: Audits Overview (NPAP, PEP, Annual PE, Flow Rate Audits) – Jeremy Howe

April 28: Calculating Bias and Precision and AQS reports – Bill Frietsche

May 5: 40 CFR 58 App. A- Gaseous Pollutants – Glenn Gehring

May 12: 40 CFR 58 App. A- Ozone – Chris Ellis, Southern Ute

May 19: 40 CFR 58 App. A- PM filter and continuous methods –Brandy Toft

Overall Course Overview:

Ozone Monitoring

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Guest Speaker:

Chris EllisSouthern Ute Indian Tribe

O3 Dependence on Meteorology

Example of ozone dependence on meteorological conditions(Ute 1 monitoring site - 8/13/02)

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14:24 14:52 15:21 15:50 16:19 16:48 17:16 17:45 18:14

Time

O3

(pp

b),

RH

(%

)

O3

RH

NO + VOCs NO2 + O2

NO2 + hv (sunlight) O + NO O + O2 O3

Ozone Formation Chemistry

Ute 3 June 1st '02 ozone vs. precursor conditions

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Time of day

O3 &

NO

x [

pp

b],

pre

cu

rso

rs

Ozone [ppb]

Temperature [ o C]

Sunlight [AU]

NO X [ppb]NO 2 [ppb]NO [ppb]

Ozone is most efficient at absorbing light near the 254 nm wavelength. (We see about 400-800 nm, green being in the middle, 254 nm shorter than violet.) Sample gas fills the absorption tube (measurement cell) and ultraviolet light at near 254 nm is sent through the sample gas; how much gets absorbed by the ozone is measured to calculate ozone conc.

Illustration is from Teledyne API 400E Operator’s manual

One problem – other gases absorb at 254 nm– therefore scrubbers used

Think of the measurement as being divided into two

steps…….•Each measurement cycle is completed

within 10 to 20 seconds.•Each measurement contains two half

cycles

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Step 1: Measuring the “clean” air

Thermo Electron/Thermo Environmental Instruments Models 49, 49C, 49i

Automated Equivalent Method: EQOA-0880-047

Zero (reference) gas with the ozone “scrubbed”

Sample

The First Measurement Half Cycle

Solenoid

Scrubber

Absorption Tubes

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UV Lamp with output concentrated at 253.7 nm where absorption of ozone is maximized

Detector: Measures the intensity of the lamp

Summary: First Measurement Half-Cycle

Ambient (outside) air is sent thru the analyzer’s solenoid valve to the scrubber where any ozone present is converted to oxygen.

This ozone-free air is sent through the absorption tubes.

The UV source lamp shines on the air and the transmitted intensity (number of photons) is measured by the detector.

The analyzer stores this intensity value.I0

Ozone Scrubber

Scrubber Cartridge

copper screens coated with manganese dioxide

The MnO2 catalyzes the reaction of ozone to diatomic oxygen.

The air entering the absorption cell after passing through the filter is the same except for the ozone.

Sample without the ozone “scrubbed”

Sample

The Second Measurement Half CycleSolenoid

Absorption Tubes

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Summary: The Second Measurement Half-Cycle

air is directed to the absorption tubes. The UV source lamp illuminates the air. Any ozone in the airabsorbs some UV light

resulting in a lower intensity value as measured by the detector.

The detector measures the transmitted intensity.

This value is subtracted from the previously stored value and the resulting difference is the amount of ozone in the ambient sample.

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Primary Standards and Transfer Standards

Primary standards have the highest authority.

Primary Standards Located at a central laboratory where it can

remain stationary, protected from the physical shocks of transportation, operated by an experienced analyst under optimum conditions.

Serves as a common standard for all analyzers in a network.

Compared against other primary standards US EPA regions have primary standards,

called SRPs, or standard reference photometers.

The Ozone Transfer Standard Think of as two instruments: half makes

ozone, the other half measures the sample. Capable of generating and measuring

accurate ozone concentrations. Can be transportable but usually not Critical Components of an Ozone Transfer

Standard: Zero air source Pump Flow controller Ozone generator Manifold

Ozone Scrubber

Pump

Flow Controller

Ozone Generator

Manifold

To analyzer part of

transfer standard

capped

Analyzer

The Ozone Generator

The Ozone Generator ultraviolet radiation (light) from a mercury

vapor lamp shines on the incoming air. The oxygen absorbs the UV light. To dissipate the resulting gain in energy, the

irradiated O2 molecules split into two negatively charged oxygen atoms.

These atoms combine with unsplit oxygen to form O3.

Ozone Generator with Ultraviolet (UV) Lamp

5 LPM

2 LPM for analyzer part of transfer standard

2 LPM + excess to analyzer

Capped

The Manifold (connector)

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QC: Patience is a Virtue Allow yourself enough time. How fast you can do it means nothing. If you rush you are bound to make mistakes. Mistakes usually cost lost data, time and

money. The best operators take their time, are

methodical and thorough.

indicated - actual

actualX 100 = Percent Difference

All checks use the same statistic: Percent Difference ( di )

1-pt QC (precision) checks:

Audit results:

d i

The .5 micron teflon® filter holder

Remember to change filter when dirty

Installed in sampling “train” before the analyzer. Will not degrade the ozone concentration. QC before changing filters regularly-audits find

dirty filters

0.5-micronTeflon® Filter

Measurement Quality Objectives (MQOs)

EPA has ozone MQOs for NAAQS meas’s Use these in element 7 of your QAPP MQOs are in validation templates

◦ Critical (any hour must be invalidated)◦ Operational (investigate, might still be okay)◦ Systematic (subsets might be invalid for

NAAQS, but data might be valid for other purposes)

MQOs (validation template)◦ Critical:

◦ 1-point QC check (used to be called precision) at least every 2 weeks conducted manually <= +7% (percent difference) Zero drift <= 2% of full scale (10 ppb away

from zero if full scale is 500 ppb) Span drift <= 7 % (e.g. near upper range of

ambient levels should show analyzer value that “drifts,” or changes less than 7% from the last span output)

Hourly values before such checks fail should be invalidated (not deleted) back to the previous passing check

Shelter temp between 20 and 30 C Annual audits should be within 15% of each

audit concentration NPAP audits should be within 10% for no

warning per conc. Verifications after moving, earthquakes

should have all points within 2% of best-fit straight line

The local ozone standard that you compare against must be certified annually

Operational criteria (investigate):

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Completeness Siting Residence time Probe material

Systematic criteria (some set of data maybe not comparable against NAAQS, but data may be usable for other purposes):

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NPAP auditing necessary for NAAQS data Your instrument may be able to do “better”

than validation criteria, see your spec sheets

Course website: http://itep68.itep.nau.edu/itep_downloads/QA101_Resources/

Our emails:◦ Chris Ellis cellis@southern-ute.nsn.us◦ Melinda.ronca-battista@nau.edu◦ Christopher.lee@nau.edu

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Ozone Monitoring Conclusions: