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What are the important parameters that need to be defined for a carbonaceous aerosol analysis ?

Hélène CACHIER Laboratoire des Sciences du Climat et de l’Environnement. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003. What are the important parameters that need to be defined for a carbonaceous aerosol analysis ?.

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What are the important parameters that need to be defined for a carbonaceous aerosol analysis ?

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  1. Hélène CACHIER Laboratoire des Sciences du Climat et de l’Environnement Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 What are the important parameters that need to be defined for a carbonaceous aerosol analysis ? How should these be documented for different analysis protocols ?

  2. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Carbonaceous Combustion Aerosols Physical and chemical diversity: their own story due to their origin source due to the atmospheric environment due to their age

  3. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Carbonaceous Combustion Aerosols morphology porous fly ash (carbonaceous) Courtesy of A. Lefèvre diesel microsoots

  4. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Carbonaceous Combustion Aerosols morphology fresh diesel microsoots Courtesy of A. Gaudichet Biomass burning particles

  5. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Carbonaceous Combustion Aerosols Atmospheric aging

  6. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Carbonaceous Combustion Aerosols Chemical complexity of EC (BC) and OC Difficult to find a chemical separation Difficult to find a thermal separation Fate of attached VOC? From D. Smith et al., 1989

  7. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Carbonaceous Combustion Aerosols Chemical complexity of the aerosol mix Biomass burning aerosols (savanna fires)

  8. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Carbonaceous Combustion Aerosols Chemical complexity of the aerosol mix Weekly samples from Finokalia (Crete) nov 01-jun02

  9. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 What type of method to be used? 2-step thermal method (Oxygen) : « blind » method TOA under Oxygen : better TOA under He and He/O2: Pyrolysis vs Combustion: don’t mix

  10. I 13TOR 11TOT 10TOT 12TOT 11bTOT 11TOT 12TOT 13TOR 10TOT 11bTOT Interlaboratory comparisons Are not consistent Discrepancy is sample dependent Schmid et al, 2001

  11. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 What to avoid ? Overlap of the 2 EC and OC components: Charring of the Organic Component Untimely removal of EC Value of optical correction ? Interferences with other species: carbonates dusts salts (K)

  12. Charring minimized Role of K (Na) Plateau temperature and duration ? Carbonates : no problem? Temperature max? Negative role of concentration loading? Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 TOA / Oxygen

  13. Temperature steps Optical (laser transmission) measurement Calibration C peaks Limit OC/EC Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 2 -step TOA example OC1 OC2 OC3 OC4 OP EC

  14. Peak (fraction) resolution BUT Important charring role of plateau temperature role of plateau duration role of concentration loading role of inorganic salt Untimely departure of EC (negative artefact) temperature of the last OC plateau Refractory OC (positive artefact) role of concentration loading role of filter matrix Reflectance or Transmittance ? Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 2- Step TOA He/He-Ox

  15. First type of 2-step TOA Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 From Chow et al.,2001

  16. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Second type of 2-step TOA From Chow et al.2001

  17. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Thermograms of levoglucosan in the (a) absence and in the (b) presence of ammonium bisulfate using the UST-2 thermal method Thermal evolution of Organic species altered by inorganic species !!! use of standard Yu et al., 2002

  18. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Yu et al., 2002 An important part of the charred OC(PEC) is from water soluble aerosol Use aerosol water extract as PEC surrogate

  19. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Thermograms of a same aerosol water extract using (a) the NIOSH and (b) the UST-3 thermal methods. Prolonging the duration at each temperature step reduces charring Yu et al., 2002

  20. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Charring corrections primarily rely on the hypothesis that charred carbon (PEC) evolves prior to EC (Native EC NEC) Hypothetic thermograms of pure PEC, pure NEC, and a mixture of the two in a HeO2 atmosphere

  21. Thermograms of (a) an untreated aerosol sample and its water extract and (b) charcoal Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Charred OC (PEC) does not evolve prior to EC (NEC)b Nor do PEC and NEC have the same absorption coefficient From Yang and Yu, 2002

  22. Whitening of the filter sample Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Analysis of a « dust» sample by the Niosh method

  23. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Recommendations Reduce charring correction uncertainty: reduce charring by increasing plateau duration reduce charring of the high temperature plateau increase the resolution around the OC/EC split point Avoid interactions with dusts (iron oxides) Proceed to removal of carbonates prior to analysis if necessary Avoid untimely departure of EC during the He step Need to find an experimental design to evaluate if OC remains on sample after the He step of the thermal procedure charring cannot be predefined Define an acceptable concentration range (mgC/cm2)

  24. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Analysis of Crete samples Minos experiment, Aug 2001 Why does the DRI-Improve mebbhod insensitive to «industrial» BC? Why is it very sensitive to Biomass Burning BC? From Sciare et al., 2003

  25. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Analysis of impactor samples Heterogeneity of the deposit Concentration of particles on small areas Role of the substrate (quartz vs aluminium)

  26. Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Are you really wanting to change your own protocole??

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