Manganese speciation in exhaust particulates of automobiles using MMT-containing gasoline

XAFS spectroscopy is used to speciate Mn-containing auto exhaust particulates emitted from MMT-added gasoline engines and collected in a controlled manner. A series of Mn compounds was also measured to model and aid quantification of the unknown species in the particulates. XANES results show that the average Mn valence in these particulates is similar to 2.2 and that MnO, Mn3O4, MnSO4. H2O and a Mn phosphate are the predominant phases present. The amount of each component varies depending on engine history and test cycle. The XAFS analysis was found to corroborate the XANES results.