Carbonaceous Particles: Practical Micro-Apportionment via 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

Average Analysis of Particles… like judging a cooking contest: mix all the entries together and then taste it carefully. CaO + Fe 2 (SO 4 ) 3 + NaCl CaCl 2 + Fe 2 O 3 + Na 2 SO 4 …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) Why single particle analysis is desired

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

EDX X-rays e 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

All particles < 0.7 micron, 8/17/00 11:08 to 11:18 AM carbonaceoushigh Nacalcite,etcamm sulfatesilica

Other mixed 4% Carbonaceous mixed with sulfates 3% Carbon-like 0% Mineral dust mixed with sulfates 62% Mixed sulfates 3% Non-mixed sulfates 23% Low C carbonaceous 1% Mineral dust 4% Particle-type composition of coarse fraction of particles (  m) 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. Particle-Type Classification Particle-type composition of fine fraction of particles (  m) Other mixed 4% Carbonaceous mixed with sulfates 10% Carbon-like 34% Mineral dust mixed with sulfates 17% Mixed sulfates 4% Non-mixed sulfates 11% Low C carbonaceous 14% Mineral dust 6%

Combustion Particles in Houston Carbonaceous Particles at the afternoon peaks 0% 20% 40% 60% 80% 100% 30-Aug-0431-Aug-041-Sep-04 EC + hydrocarbon C 1 O 0.16 N 0.01 CO 0.23 N 0.02 Carbonaceous Particles at midnights 0% 20% 40% 60% 80% 100% 30-Aug-0431-Aug-041-Sep-04 Carbonaceous particles fall into 3 simple groups: Very low Oxygen (B.C.) 20 to 40 % O 20 to 40 % O % S Other traces: Ti, Mg, Na,Ca, V, Fe, N, Pb… are sporadic EC + … CO 0.30 N 0.01 CO 0.21 N 0.01 CO 0.29 N 0.01 S 0.08 CO 0.25 N 0.01 S 0.08 CO 0.20 N 0.01 S 0.08 CO 0.30 N 0.00 CO 0.45 N 0.00 CO 0.40 N 0.01 S 0.12 CO 0.30 N 0.00 S 0.17 CO 0.33 N 0.04 S 0.12 CO 0.30 N 0.02 EC + …

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

Tracers Mn, K ?

All particles < 0.7 micron, 8/17/00 11:08 to 11:18 AM carbonaceoushigh Nacalcite,etcamm sulfatesilica

Note in Previous slide, that many SiO 2 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!

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