CHARACTERISTICS OF NANOPARTICLE EMISSIONS FROM AN AGED DIESEL VEHICLE FUELLED WITH BIODIESEL B7

Emissions from aging diesel vehicles represent a major environmental and public health concern, particularly in view of the widespread use of biodiesel blends in existing fleets. This study investigates the nanoparticle emissions from an aged diesel passenger vehicle fuelled with biodiesel B7 under simulated driving conditions. The numbers and mass concentrations of the particles and their size distributions, morphology, and elemental composition are recorded at engine start-up, while driving at low (50 km/h) and high speeds (100 km/h), and after driving, using a chassis dynamometer and multiple measurement techniques. The particulate emissions are found to be dominated by ultrafine particles (<100 nm). The number concentrations vary between 1.35 × 10⁷ particles/cm³ during engine start-up and 2.60 × 10⁷ particles/cm³ during high-speed driving, with concentrations inside the exhaust pipe approximately 7.8 times higher than those measured outside. Morphological analysis reveals a transition from compact agglomerates under low-speed conditions to fractal-like, porous aggregates at high speed. Higher proportions of iron (Fe) and sulphur (S) are found during high-speed driving, suggesting influences from engine wear and lubricant-related sources. The small sizes and high reactivity of these particles allow them to penetrate into the lungs and enter the bloodstream, posing respiratory and cardiovascular health risks. Characterisation based on particle numbers and physicochemical properties is therefore preferable to mass-based emission metrics in terms of capturing the health-related features of diesel exhaust. Ultrafine particle exposure should be prioritised in environmental and occupational health risk assessments, particularly in regions with a high proportion of aging diesel vehicles.