Chemical Analysis of Individual Aerosols Particles by Electron Energy-Loss Spectroscopy (EELS)
Abstract
We use electron energy-loss spectroscopy (EELS) with a transmission electron microscope (TEM) to obtain chemical and bonding information on individual aerosol particles. EELS is ideally suited to this task because of its high spatial resolution and sensitivity to light elements such as C, N, and O. In addition, the spectral shapes provide information regarding bonding, atomic coordination and, for polyvalent elements, oxidation states. Our current focus is on carbonaceous aerosols both in the ambient air and emissions from biomass burning, with emphasis on the heterogeneous chemistry, particle structure, and chemical composition of soot particles. From the EELS spectra we were able to record for the first time, differences in composition between individual spherules within the same soot aggregate. We also found evidence of chemical variations even within individual soot spheres as small as 50 nm across. In the case of biomass burning, the most striking chemical differences are in the quantity of K, minor O and, in places, N. The quantity of elements associated with C decreases with the degree of graphitization of the soot spheres, as shown by the shapes of the C spectra and was corroborated by high-resolution TEM images of the analyzed particles. Knowledge of the degree of graphitization and quantity of associated elements is important for understanding and modeling their optical properties and in some case in source attributions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AGUFM.A11B..04B
- Keywords:
-
- 0305 Aerosols and particles (0345;
- 4801);
- 0345 Pollution: urban and regional (0305);
- 0365 Troposphere: composition and chemistry;
- 0394 Instruments and techniques