Two-stroke scooters are a dominant source of air pollution in many cities

by admin / Cities&Events
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I know lot of people that decided to use scooter instead a car to be greener but this group of scientists has done some research and it seems just the opposite.

“Fossil fuel-powered vehicles emit significant particulate matter, for example, black carbon and primary organic aerosol, and produce secondary organic aerosol. We quantifyed secondary organic aerosol production from two-stroke scooters. Cars and trucks, particularly diesel vehicles, are thought to be the main vehicular pollution sources. This needs re-thinking, as we show that elevated particulate matter levels can be a consequence of ‘asymmetric pollution’ from two-stroke scooters, vehicles that constitute a small fraction of the fleet, but can dominate urban vehicular pollution through organic aerosol and aromatic emission factors up to thousands of times higher than from other vehicle classes. Further, we demonstrate that oxidation processes producing secondary organic aerosol from vehicle exhaust also form potentially toxic ‘reactive oxygen species’.

Particulate matter (PM) damages health and affectsclimate. Road vehicles are a significant source of PM,particularly in urban areas. A number of recent studies have shown that a large fraction, possibly the largest, of vehicular PM is secondary organic aerosol (SOA) produced via atmospheric oxidation of precursor gases in the exhaust3–5. Thus, understanding vehicular air pollution requires an assessment of SOA formation from different vehicle types. Two-stroke (2S) scooters (powered two-wheeled vehicles with engine displacement r50 cm3) are popular globally, particularly in Asia, Africa and Southern Europe. Despite being high emitters of primary PM6,7, regulations for scooters are generally less stringent than for other vehicles, for example, in Europe having reached Euro 5/V (a fifth tranche of regulations), for passenger cars and trucks, versus only Euro 2 for scooters. Accordingly, a scientific report to the European Commission suggests that scooters will emit more volatile organic compounds (VOCs) than all other vehicles combined in Europe by 2020. Furthermore, high PM levels and toxic aromatic hydrocarbons, important SOA precursors, have been observed in many cities, especially in Asia. Globally, organic aerosol (OA) dominates PM, with SOA accounting for the largest fraction.

We show that 2S scooters emit significant amounts of primary organic aerosol (POA), aromatic VOCs and also produce significant SOA. We use the term ‘asymmetric polluter’ to describe these vehicles as their emission factors (EFs) and evidence from air quality measurements before and after bans on scooters in Asian cities suggest they may dominate vehicular pollution despite their relatively small numbers. Chemical analysis of the emissions shows that SOA is mainly produced via photo-oxidation of aromatic VOCs, present in gasoline, from the exhaust. This shows that the known issue of incomplete fuel combustion during the 2S cycle is also responsible for SOA formation. Finally, we present the first online measurements of aged exhaust showing that SOA formation also produces reactive oxygen species (ROS) with potentially detrimental effects on
our lungs.”

S.M. Platt, I. El Haddad, S.M. Pieber, R.-J. Huang, A.A. Zardini, M. Clairotte,w, R. Suarez-Bertoa, P. Barmet, L. Pfaffenberger, R. Wolf, J.G. Slowik, S.J. Fuller, M. Kalberer, R. Chirico,w, J. Dommen, C. Astorga, R. Zimmermann, N. Marchand, S. Hellebust, B. Temime-Roussel, U. Baltensperger & A.S.H. Pre´voˆt.





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