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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.

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Presentation on theme: "What are the important parameters that need to be defined for a carbonaceous aerosol analysis ? Hélène CACHIER Laboratoire des Sciences du Climat et de."— Presentation transcript:

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2 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 How should these be documented for different analysis protocols ?

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

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

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

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

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

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

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

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

11 11TOT10TOT 11bTOT 12TOT 11TOT10TOT 11bTOT 13TOR I Interlaboratory comparisons Are not consistent Discrepancy is sample dependent Schmid et al, 2001

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

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

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

15 2- Step TOA He/He-Ox Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 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) Refractory OC (positive artefact) temperature of the last OC plateau Reflectance or Transmittance ? role of concentration loading role of filter matrix

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

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

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

19 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

20 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 Laboratoire des Sciences du Climat et de l ’Environnement Durando ECOC workshop, March 2003 Yu et al., 2002

21 Hypothetic thermograms of pure PEC, pure NEC, and a mixture of the two in a HeO2 atmosphere 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)

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

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

24 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 Define an acceptable concentration range (  gC/cm2) charring cannot be predefined

25 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

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

27 Are you really wanting to change your own protocole??


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