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CSN Data Overview for OC/EC Artifact Adjustments

This presentation reviews the artifact adjustment approach for CSN, focusing on sampler-specific variations and blank data. It covers the analyses from 2000 to present, including types of samplers, timeline, lab blanks, and more. The data includes OC and EC fractions analyzed by different laboratories. Various sampler types are discussed, along with field and trip blanks collected and analyzed at different frequencies. Furthermore, the lab QC data for original OC/EC analyses is detailed, including acceptance blanks, instrument blanks, duplicate and replicate analyses. The available blank types with the 3000N sampler protocol are also explored, alongside the analysis of afterfilters and TOT levels. The presentation sheds light on the reliability and statistical calculations derived from the data, offering insights into the CSN program's findings and adjustments for OC/EC artifacts.

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CSN Data Overview for OC/EC Artifact Adjustments

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  1. Overview of CSN Data Relevant to OC/EC Artifact Adjustmentspresented byJames FlanaganRTI InternationalDavis, CAJanuary 22-23, 2008

  2. Assignment: “Review of current artifact adjustment approach for CSN, including sampler-specific variations” • There is no artifact adjusted data currently being posted to AQS for any CSN species, therefore this presentation will focus on: • Blank data available that could be used for artifact adjustments: • Original CSN samplers and analysis • New 3000N samplers and analysis • CSN program timeline • CSN sampler types • Blank level differences between sampler types • Lab blanks and other QC data

  3. CSN Timeline 2/9/2000 – 7/7/2003 OC, EC analyses done by RTI International Laboratory using Sunset Labs Instruments No OC or EC fractions (“peaks”) reported “OCX” or “OCX2” were reported during this period 7/8/2003 – present OC, EC analyses for CSN samplers done by RTI International Laboratory. 4 OC fractions (plus Pyrolysis C) are reported; no OCX or OCX2. no EC fractions reported. -- Initial Set of 55 3000N Samplers Added to CSN in May, 2007 -- 5/2007 – present 3000N filters are being analyzed by Desert Research Inst. (DRI). 3000N samplers are collocated with the existing CSN samplers at each site, and are run collocated for 2 months 4 OC, Pyrolysis C, and 3 EC fractions, plus OC and EC by TOT and TOR are being uploaded to AQS without artifact correction.

  4. CSN: “STN” TOT Analysis Method • Filter: 47mm Whatman quartz w/ 5% borosilicate binder • Filters pre-fired at 900oC in air • Sunset Lab Carbon Aerosol Analyzers • Protocol: NIOSH 5040, optimized for PM2.5 • Time-driven analysis (12 min total) • Thermal-Optical Transmittance (TOT)

  5. CSN Sampler Types • URG MASS – Wins Impactor; Teflon module • Andersen RAAS - cyclone; Teflon coated module • MetOne SASS – mini-cyclone; alloy module • other types: • R&P 2300 – internal greased impactor; alloy module • R&P sequential FRM

  6. CSN Sampler Module Types URG MASS Andersen RAAS Cassette used for IMPROVE and 3000N Samplers MetOne SASS R&P 2300

  7. CSN: Field and Trip Blanks(reported to AQS) • Field Blanks are collected at 10% of routine frequency (monthly or bimonthly at each site) – filter modules mounted for a short period of time and removed. • Trip Blanks are collected at 3% of rout. freq. – filter modules not removed from shipping bag. • Field and Trip Blank results are very similar. • Field/Trip Blank levels differ significantly between sampler types.

  8. CSN: Field/Trip Blank Averages(Original OC/EC Analyses) Trip and Field Blank averages 2000 – 2006, ug/filter * * R&P module contains silicone impactor grease, which may appear as EC. • 47 mm Whatman filter with borosilicate binder. • CSN (STN) analysis protocol. • Each number is 100’s or 1000’s of measurements. Source: Max R. Peterson, James B. Flanagan, Larry C. Michael, and R.K.M. Jayanty. 2007. Analysis of PM2.5 Speciation Network Carbon Blank Data. AAAR 26th Annual Conference, Reno, NV, September 24-28.

  9. CSN: Laboratory QC Data for Original OC/EC Analyses(not reported to AQS) • Analyses are performed by RTI International’s OC/EC Laboratory in North Carolina using Sunset Labs Instruments. • Acceptance Blanks — full STN analysis of the larger of 2 or 2% of pre-fired filters. • Instrument Blanks — full STN analysis using a clean filter punch, usually from the preceding analysis. • Duplicate Analyses —10% of filter samples reanalyzed on the same analyzer to test uniformity of filter deposit. • Replicate Analyses — a group of filters analyzed on 3 or more analyzers to assess between-analyzer variability and to establish measurement uncertainties.

  10. CSN: Laboratory QC Data Received for OC/EC 3000N(not reported to AQS) • Analyses are being done by Desert Research Institute (DRI) in Reno, NV. • System Blanks — Full IMPROVE_A analysis without a filter punch. • Replicate Analyses — Analysis of a second punch from 10% of filter samples on a randomly-chosen (different or same) analyzer used to evaluate between-analyzer variability. • DRI performs additional QC not reported to RTI.

  11. CSN: Available Blank Types with 3000N Sampler Protocol(blank data reported to AQS) • Afterfilters – identical to IMPROVE NEW to CSN • IMPROVE-type “field blanks” (passive blank in 4th position of cassette) NEW to CSN • Field Blanks (like existing CSN Trip and Field Blanks)

  12. Afterfilters – Frequency and Availability of Data for Statistics • Since May, 2007, CSN runs afterfilters at all sites equipped with 3000N at a rate of 10% • Sufficient afterfilter data are available to calculate reliable statistics on a monthly basis • Median • Standard Deviation • other?

  13. TOT Afterfilter vs. Ambient Levelswith 3000N Module Original CSN field and trip blanks are generally poorly correlated to season or site location; however, afterfilters from 3000N show some correlation with ambient levels. • Data from 3000N: • X-axis = front filter • Y-axis = afterfilter • N = 820, R2=0.2378 • 55 sites nationwide • 5/2007 – 12/2007

  14. CSN: Temporal Variability in Trip and Field Blank Levels Average Total Carbon Blank by Year, ug/m3 (subset of sites with long-term data) • Between 2002 and 2005, STN field and trip blank annual averages for Met One (SASS) and Anderson (RAAS) samplers decreased 33% and averages for URG (MASS) samplers increased 25%. From “Carbon Measurements and Adjustments “, presented by Neil Frank at Air Quality Data in Health Effects Research conference, Nov 30 – Dec 1, 2006

  15. From “Carbon Measurements and Adjustments “, presented by Neil Frank at Air Quality Data in Health Effects Research conference, Nov 30 – Dec 1, 2006

  16. CSN: Temporal Variability in Trip and Field Blank Levels MetOne Sampler Total Carbon Field and Trip Blanks, μg/m3 From “Carbon Measurements and Adjustments “, presented by Neil Frank at Air Quality Data in Health Effects Research conference, Nov 30 – Dec 1, 2006

  17. Lab Blank Variability “Second” “Third” • Instrument blanks are typically less than 10% of trip and field blanks when expressed in the same units • Between-instrument variability and the effect of a software upgrade are visible • One of the lab analyzers appears to be more sensitive to the software change than the other. Source: Max R. Peterson, James B. Flanagan, Larry C. Michael, and R.K.M. Jayanty. 2007. Analysis of PM2.5 Speciation Network Carbon Blank Data. AAAR 26th Annual Conference, Reno, NV, September 24-28.

  18. Notable Differences Between Original CSN Method and IMPROVE/3000N • Face velocity and deposit density are potentially up to 10x greater for IMPROVE/3000N relative to MetOne due to flow rate and filter size. • Different filter materials. • Different flow control technology (IMPROVE) • Different analysis protocols: • temperature steps • timebase • TOT vs. TOR

  19. Summary Slide: Pros and Consfor the use of existing field and trip blank data for artifact correction of original CSN data • Pro: Lots of existing data 2000 - present • Pro: Probably closer to truth than lab blanks • Con: May not represent “true” artifact • Con: Questionable relevance to IMPROVE data • Con: Unlike afterfilters, the existing CSN trip and field blanks are not sensitive to seasonal or geographic variations

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