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Carbon Artifact Adjustment in IMPROVE

This article discusses sampling artifacts for particulate carbon measurement, including passive positive artifacts, active positive artifacts, and active negative artifacts. It explains the impact of artifacts on secondary filters and provides methods for adjustment. Examples of field blanks and the time history of carbon artifacts are also discussed.

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Carbon Artifact Adjustment in IMPROVE

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  1. Carbon Artifact Adjustment in IMPROVE Lowell Ashbaugh Crocker Nuclear Lab University of California, Davis January 22, 2008

  2. Sampling Artifacts for Particulate Carbon • Passive positive artifact • Quartz filter adsorbs volatile organic gases passively upon exposure to the atmosphere without airflow • Active positive artifact • Quartz filter adsorbs volatile organic gases during sampling • Active negative artifact • Volatile organic particles dissociate into gases during sampling and are lost to the filter

  3. Result of Artifact on Secondary Filter (CS) • Passive positive artifact • CS = CP → Subtract CS from CP • Active positive artifact • CS = fraction of CP → Subtract CS/(1-eff) from CP • Active negative artifact • CS = “lost” VOP from CP → Add CS to CP

  4. IMPROVE assumes all positive artifact CP – quartz front filter CS – quartz backup filter (median of monthly values from 6 sites) Particulate OC = CP – CS Field blanks All sites A few each year No air flow through blanks In sampler for 7 days Supported by research D. Fitz (1990), AS&T 12:142-148 IMPROVE OC Measurements

  5. IMPROVE sites with CS filters

  6. Time history of carbon artifacts

  7. Histograms for July 2005

  8. Monthly CS measurements by site

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