Gas and particle phase polycyclic aromatic hydrocarbon emission factors from a diesel vehicle engine : effect of operating modes in a developing country context

Abstract

Airborne polycyclic aromatic hydrocarbons (PAHs) arising from diesel exhaust emissions are of concern due to their significant human health and environmental impacts. Engine dynamometer experiments with a light duty diesel engine were conducted to measure PAH emissions representative of developing country conditions, and thereby determine emission factors at two different engine operating modes that are representative of idling and severe real-world conditions, respectively. We employed a portable denuder device for the simultaneous sampling of gaseous and particulate PAH emissions, the components of which were subsequently individually thermally desorbed and analysed by two-dimensional gas chromatography with time-of-flight mass spectrometric detection (TD-GCxGC-ToF-MS). Results indicated that PAH emission factors differed significantly for the different modes of engine operation with the highest emission factor being for idle mode with a total PAH emission factor of 1181.14 μg/kg. Under real-world conditions, it is expected that further variance in emission factors will be introduced as a result of brake and tyre wear, different engine technologies, engine age and maintenance, as well as fuel quality and measurement methods