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Toxic Impacts of Emissions from Small 50cc Engine Run under EC47 Driving Cycle: A Comparison between 2-Stroke and 4-Stroke Engines and Lube Oil Quality and Ethanol Additivation
Abstract:
One 4-stroke scooter and two 2-stroke scooters (50 cc bore) were run on dynamic test benches according to the EC47 driving cycle. Emissions from these scooters were continuously monitored, sampled and hot- diluted prior being driven to continuous flow through chambers containing organotypic cultures of lung tissue under bi-phasic Air/liquid culture conditions for three hours. Lung tissue was evaluated for viability (ATP), anti-oxidant defenses (intracellular GSH, Catalase, superoxide-dismutases, glutathione-S-Transferase, glutathione peroxidase, glutathione-reductase activity levels) and inflammatory reaction through the measurement of TNFalpha secretion in the culture medium.
4-stroke engine emissions had a moderate impact on lung tissue viability but induced a marked GSH depletion concomitant of increased GPx activity.
2-strokes engine emissions had variable impacts according to after-treatment technology and lube oil quality. Lower oxidation catalysis and mineral lube oil were found to be the worse situation inducing a marked lung tissue viability loss and high intracellular glutathione depletion, a marked decrease in SOD activity both Mn and Cu/Zn iso-enzymes being affected and a decrease in TNF alpha secretion. On the other hand, thigh oxidation catalysis and semi-synthetic lube oil was found to be the best situation with only minor tissue viability loss, moderate glutathione depletion, moderate elevation of glutathione peroxidase, almost no impact on superoxide dismutase activities and a moderate increase in TNFalpha secretion.
The measurement of regulated emissions (CO, NO, NO2, HC, and particulate matter showed that under warm engine conditions, 2-stroke engine with high oxidation catalysis and semi-synthetic lube oil was the least emitting situation especially when CO, HC and particulate matter are considered. 4-stroke engine proved to have intermediate emissions levels especially for CO, HC and particulate matter. 2-stroke engine with low oxidation catalysis and mineral oil was found to be the worse situation especially for HC and particulate matter.
In conclusion : emissions from small scooters may have detrimental impacts on lung tissue which may be highly reduced by the use of an oxidation catalyst on the exhaust line and by using high quality grade oil like semi-synthetic oil compared to mineral oil. Suitable recently designed after-treatment strategies allow a very efficient reduction of 2-stroke engine emissions and toxic potential leading to an even lesser impact than for the 4stroke commercially available engine emissions.