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Carbonaceous Particles: Practical Micro-Apportionment via Single Particle SEM/EDX
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  1. Carbonaceous Particles:Practical Micro-Apportionmentvia Single Particle SEM/EDX Alex Laskin, Martin Iedema, James Cowin Pacific Northwest National Laboratory Richland, Washington Micro-Apportionment O/C ratios Better use of marker elements Sec. Org. Carbon Coating of Minerals

  2. Why single particle analysis is desired Average Analysis of Particles… like judging a cooking contest: mix all the entries together and then taste it carefully. CaO + Fe2(SO4)3 + NaCl CaCl2 + Fe2O3 + Na2SO4 …in terms of history, sources, chemistry, haze, health effects. 1 ppm As inside each soil particle vs 1 in million pure As particle Thin coating of ammonium sulfate can make a particle hydroscopic. So much to know… Particle mix A) Particle mix B)

  3. Single Particle Methods Single Particle Mass Spectrometry Good, but bulky, not so quantitative Scanning Electron Microscopy + x-ray analysis (+ extra) Need to it better, faster than usual state of the art AND need good time-resolved field collector

  4. EDX e X-rays Automated Time-Resolved Aerosol Collector (TRAC) 1 to 10 minute resolution Lab analysis up to 50,000 particles/day Down to 0.2 microns Elements >= C QUANTITATIVELY

  5. high Na calcite,etc amm sulfate silica carbonaceous

  6. Particle-Type Classification Particle-type composition of fine fraction of particles (0.2-0.7 mm) Particle-type composition of coarse fraction of particles (0.7-2.5 mm) Mineral dust 6% Carbon-like 34% Low C carbonaceous 14% Mineral dust 4% Carbon-like 0% Other mixed 4% Low C carbonaceous 1% Carbonaceous mixed with sulfates 3% Non-mixed sulfates 11% Non-mixed sulfates 23% Mixed sulfates 4% Mineral dust mixed with sulfates 17% Mineral dust mixed with sulfates 62% Other mixed 4% Carbonaceous mixed with sulfates 10% Mixed sulfates 3% An example of classification results based on the EDX data of “fine” and “coarse” particles in an individual sample. Carbon-like particles are those for which their EDX spectra show no elements different from the background (Cu and C), at some extent they can be considered to be mostly carbonaceous particles with high carbon concentration.

  7. Combustion Particles in Houston Carbonaceous Particles at the afternoon peaks Carbonaceous particles fall into 3 simple groups: Very low Oxygen (B.C.) 20 to 40 % O 20 to 40 % O + 1-10% S Other traces: Ti, Mg, Na,Ca, V, Fe, N, Pb… are sporadic 100% CO0.29N0.01S0.08 CO0.25N0.01S0.08 CO0.20N0.01S0.08 CO0.21N0.01 CO0.23N0.02 80% CO0.30N0.01 60% EC + hydrocarbon EC + … C 40% 1 O EC + … 0.16 N 20% 0.01 0% 30-Aug-04 31-Aug-04 1-Sep-04 Carbonaceous Particles at midnights 100% CO0.40N0.01S0.12 CO0.30N0.00S0.17 80% CO0.30N0.00 CO0.45N0.00 CO0.33N0.04S0.12 60% 40% CO0.30N0.02 EC + … EC + … 20% EC + … 0% 30-Aug-04 31-Aug-04 1-Sep-04

  8. Tracers Zn, Ti ? Not good tracers…. BUT with single particle data AND good Average compositional data (PIXE, XRF), one can do outstanding source apportionment !!!!!

  9. Tracers Mn, K ?

  10. high Na calcite,etc amm sulfate silica carbonaceous

  11. Note in Previous slide, that many SiO2 particles have carbonaceous coatings. This is pure, secondary organic particle material. • This is an excellent whey of monitoring SOC, and possible catalytic role of substrate particle in forming them!

  12. Conclusion Micro-apportionment via single particle SEM/EDX adds unique data, which can greatly facilitate source apportionment of carbonaceous particles, including secondary ones O/C ratios Better use of marker elements Sec. Org. Carbon Coating of Mineral Practical, cheap field deployment of time resolved and/or time integrated and/or mobile collectors Very quantitative