Composition of semi-voloatile particles from Diesel exhaust
Résumé
Vehicle exhaust particles from diesel passenger vehicleswere studied in terms of volatility and chemicalcomposition. Condensation of semi-volatile compoundsleads to particle growth during exhaust dilution andcooling. The particle growth was observed to be particlesurface related. At higher vehicle speed and load someof the semi-volatile material forms nucleation particlesthat are dominating the particle number concentration.The nucleation mode is completely volatile at 180°C andconsists mainly of sulfate. The amount of organicmaterial is smaller. The organics/sulfate ratio is larger forthe soot mode indicating an earlier condensation processof organics before they are incorporated in the nucleationprocess. Under typical atmospheric dilution conditionsmost of the semi-volatile material is present in the sootmode. The semi-volatile material evaporates attemperature between 130°C and 180°C. Thermaltreatment using a thermodenuder enables completeevaporation of the nucleation particles, however not allmaterial from the soot particles is removed.