Presentation on theme: "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."— Presentation transcript:
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 1
2 Guest Speaker: Chris Ellis Southern Ute Indian Tribe
NO + VOCs NO 2 + O 2 NO 2 + hv (sunlight) O + NO O + O 2 O 3
Ozone is most efficient at absorbing light near the 254 nm wavelength. (We see about 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 Operators manual One problem – other gases absorb at 254 nm– therefore scrubbers used
Each measurement cycle is completed within 10 to 20 seconds. Each measurement contains two half cycles
Zero (reference) gas with the ozone scrubbed Sample The First Measurement Half Cycle Solenoid Scrubber Absorption Tubes I0I0
UV Lamp with output concentrated at nm where absorption of ozone is maximized
Detector: Measures the intensity of the lamp
Ambient (outside) air is sent thru the analyzers 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. I0I0
Scrubber Cartridge copper screens coated with manganese dioxide The MnO 2 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 Cycle Solenoid Absorption Tubes I
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. I I – I 0
Primary standards have the highest authority.
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.
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
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 O 2 molecules split into two negatively charged oxygen atoms. These atoms combine with unsplit oxygen to form O 3.
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)
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 actual X 100 = Percent Difference All checks use the same statistic: Percent Difference ( d i ) 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
EPA has ozone MQOs for NAAQS meass 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)
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 32
Completeness Siting Residence time Probe material 33
NPAP auditing necessary for NAAQS data Your instrument may be able to do better than validation criteria, see your spec sheets Course website: A101_Resources/ A101_Resources/ Our s: Chris Ellis 34