Overview of CSN Data Relevant to OC/EC Artifact Adjustments

presented byJames FlanaganRTI International

Davis, CAJanuary 22-23, 2008

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

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.

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)

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

CSN Sampler Module TypesAndersen RAAS

URG MASS

MetOne SASS

R&P 2300

Cassette used for IMPROVE and 3000N Samplers

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.

CSN: Field/Trip Blank Averages(Original OC/EC Analyses)

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.

Trip and Field Blank averages 2000 – 2006, ug/filter

• 47 mm Whatman filter with borosilicate binder.• CSN (STN) analysis protocol.• Each number is 100’s or 1000’s of measurements.

* R&P module contains silicone impactor grease, which may appear as EC.

*

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.

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.

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)

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?

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.

Backup "Concentration" vs. Routine Concentration May 2007 - Dec 2007

0.0

0.5

1.0

1.5

2.0

0 5 10 15 20

Routine (Ambient) Conc., ug/m3

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, ug

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OC IMPROVE TOT

R2 = 0.2378

Data from 3000N:

• X-axis = front filter• Y-axis = afterfilter• N = 820, R2=0.2378• 55 sites nationwide• 5/2007 – 12/2007

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%.

Average Total Carbon Blank by Year, ug/m3 (subset of sites with long-term data)

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

CSN: Temporal Variability in Trip and Field Blank Levels

Sampler Type N sites 2001 2002 2003 2004 2005

Andersen RAAS 22 1.19 1.5 1.03 0.9 0.99MetOne SASS 140 1.53 1.63 1.21 1.01 1.09URG MASS 5 0.29 0.34 0.25 0.26 0.43

Trip/Field Blank Averages

ug/m3

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2000 2001 2002 2003 2004 2005 2006

Year

Tri

p/F

ield

Bla

nk

Ave

rag

e, u

g/m

3

Andersen

MetOne

URG

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

To

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arb

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Tri

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CSN: Temporal Variability in Trip and Field Blank Levels

MetOne Sampler

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

Lab Blank Variability

• 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.

“Second” “Third”

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

Summary Slide: Pros and Cons for 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