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Emissions and Secondary Formation of Air Pollutants From Modern Heavy-Duty Trucks in Real-World Traffic – Chemical Characteristics Using on-Line Mass Spectrometry
LIYUAN ZHOU, Christian M. Salvador, Michael Priestley, Mattias Hallquist, Qianyun Liu, Chak K. Chan, Åsa M. Hallquist, City University of Hong Kong, China
Abstract Number: 198
Working Group: Aerosol Chemistry
Abstract
Complying with stricter emissions standards, a new generation of heavy-duty trucks (HDTs) has gradually increased its market share and now accounts for a large percentage of on-road-mileage. The potential to improve air quality depends on an actual reduction in both emissions and subsequent formation of secondary pollutants. In this study, the emissions in real-world traffic from Euro VI compliant HDTs were compared to older classes, represented by Euro V, using High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometry (HR-ToF-CIMS). Gas phase emissions of several hundred species were observed for 70 HDTs. Further, the particle phase and secondary pollutant formation were evaluated for a number of HDTs. The reduction of primary EFs was evident (~ 90%) and in-line with a reduction of 28–97% in typical regulated pollutants. Secondary production after photochemical ageing in an oxidation flow reactor exceeded the primary emissions (EFAged/EFFresh ratio ≥ 2). Organic acids and byproducts from urea-selective catalytic reduction (SCR) systems had both primary and secondary sources. A non-negative matrix factorization (NMF) analysis highlighted the issue of vehicle maintenance as a remaining concern. However, the adoption of Euro VI has a significant positive effect on emissions in real-world-traffic and should be considered in e.g. urban air quality assessment.