Research on automobile exhaust particles by STXM and NEXAFS

In order to understand the structures of automobile exhaust particles and the components of nitrogen inside them, automobile exhaust particles from Santana 3000 and Golcars are investigated with scanning transmission X-ray microscopy (STXM) and the near edge X-ray absorption fine structure (NEXAFS) spectra. The results of STXM show that single particulate has a size of 500 nm and a nonuniform mass distribution with an empty hole inside it. Compared with the NEXAFS spectra, (NH(4))(2)SO(4) and NaNO(3) spectra show many different sigma* resonances at 406 eV, the spectrum of ammonium has a shoulder structure. NaNO(3) and automobile exhaust particles show significant sigma resonances at 412 eV and 418. 5 eV. However, (NH(4))(2)SO(4) shows wider sigma resonances 413. 5 eV and 421. 8 eV. Nitrates are main chemical species of nitrogen in automobile exhaust particles. In an energy range from 395 eV to 418 eV,Santana 3000 automobile exhaust particles are stack scanned. The principal component analysis and cluster analysis indicate that there exist nitrates in surface layer and minor ammonium inside it.