Abstract
Abstract. The transition, in extent and characteristics, of atmospheric emissions caused by the modernization of the heavy-duty on-road fleet was studied utilizing roadside measurements. Emissions of particle number (PN), particle mass (PM), black carbon (BC), nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbon (HC), particle size distributions, and particle volatility were measured from 556 individual heavy-duty trucks (HDTs). Substantial reductions in PM, BC, NOx, CO, and to a lesser extent PN were observed from Euro III to Euro VI HDTs by 99 %, 98 %, 93 %, and 57 % for the average emission factors of PM, BC, NOx, and CO, respectively. Despite significant total reductions in NOx emissions, the fraction of NO2 in the NOx emissions increased continuously from Euro IV to Euro VI HDTs. Larger data scattering was evident for PN emissions in comparison to solid particle number (SPN) for Euro VI HDTs, indicating a highly variable fraction of volatile particle components. Particle size distributions of Euro III to enhanced environmentally friendly vehicle (EEV) HDTs were bimodal, whereas those of Euro VI HDTs were nucleation mode dominated. High emitters disproportionately contributed to a large fraction of the total emissions with the highest-emitting 10 % of HDTs in each pollutant category being responsible for 65 % of total PM, 70 % of total PN, and 44 % of total NOx emissions. Euro VI HDTs, which accounted for 53 % of total kilometres driven by Swedish HDTs, were estimated to only contribute to 2 %, 6 %, 12 %, and 47 % of PM, BC, NOx, and PN emissions, respectively. A shift to a fleet dominated by Euro VI HDTs would promote a transition of atmospheric emissions towards low PM, BC, NOx, and CO levels. Nonetheless, reducing PN, SPN, and NO2 emissions from Euro VI HDTs is still important to improve air quality in urban environments.
Highlights
Vehicular emissions contribute significantly to gaseous and particle pollutants in the urban atmosphere, and descriptions of their extent and characteristics are key input components for urban air quality modelling
The emission factors of particle mass (PM), non-volatile particle number (PN), and nitrogen oxides (NOx) showed little variation (R2 ≥ 0.77) among multiple passages of the same heavy-duty trucks (HDTs); higher variability was observed in the PN emissions
The gaseous emissions of NOx and carbon monoxide (CO) showed a significant decrease with respect to Euro class (Jonckheere–Terpstra test, p < 0.01), while the HC emission was relatively low for all the HDT Euro class types
Summary
Vehicular emissions contribute significantly to gaseous and particle pollutants in the urban atmosphere, and descriptions of their extent and characteristics are key input components for urban air quality modelling. In Europe, the introduction of new legislation, especially Euro VI, has aimed to reduce emissions of many pollutants. Legislation exists for particles (mass and number) and selected gases; there are many components of the emissions that are not directly regulated but are potentially detrimental to human health. In the most recent European emission standard (Euro class), this has partly been covered by introducing a limit on the solid particle number (SPN), while volatile particles and Published by Copernicus Publications on behalf of the European Geosciences Union
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