A transition in atmospheric emissions of particles and gases fromon-road heavy-duty trucks

2019 
Abstract. The transition in extent and characteristics of atmospheric emissions caused by the modernisation of the heavy-duty on-road fleet were studied utilising 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 emissions 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 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, respectively. 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. A shift to a Euro VI HDTs dominant fleet 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.
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