In this study, the microstructure and oxidation behaviour of soot from the raw exhaust of a Euro IV test heavy duty (HD) diesel engine is investigated and compared to that of spark discharge soot and hexabenzocoronene (HBC, C 42 H 18 ). We find a microstructure-controlled reactivity toward oxidation of all three samples in 5% O 2 in N 2 . The spark discharge soot with its fine primary particles and fullerenoid structure has an onset temperature of 423 K for combustion, while the hexabenzocoronene with its well-ordered crystallites has a high onset temperature of 773 K. Due to an improved combustion process in the Euro IV HD diesel engine, the soot emitted consists of more fullerenoid-like or onion-like particles agglomerated in a chain-like secondary structure. The onset temperature of the Euro IV HD engine soot combustion is 573 K. Oxidation of the three samples produces only CO 2 and H 2 O. The different H 2 O production profiles can be assigned to the functionalised surface of the samples and depend on the soot structures and preparation route.

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