Abstract
Studies on the characteristics of hazardous air pollutants (HAPs) in the emissions of medium-duty diesel trucks are significantly insufficient compared to those on heavy-duty trucks. This study investigated the characteristics of regulated pollutants and HAPs, such as volatile organic compounds (VOCs), aldehydes, and polycyclic aromatic hydrocarbons (PAHs), and estimated non-methane hydrocarbon (NMHC) speciation in the emissions of medium-duty diesel trucks. Ten medium-duty diesel trucks conforming to Euros 5 and 6 were tested for four various driving cycles (WLTC, NEDC, CVS-75, and NIER-9) using a chassis dynamometer. In an urban area such as Seoul, CO and NMHC emissions were increased because of its longer low-speed driving time. NOx emissions were the highest in the high-speed phase owing to the influence of thermal NOx. PM emissions were almost not emitted because of the DPF installation. Alkanes dominated non-methane volatile organic compound (NMVOC) emissions, 36–63% of which resulted from the low reaction of the diesel oxidation catalyst. Formaldehyde emissions were the highest for 35–53% among aldehydes irrespective of driving cycles. By sampling the particle-phase of PAHs, we detected benzo(k)fluoranthene and benzo(a)pyrene and estimated the concentrations of the gas-phase PAHs with models to obtain the total PAH concentrations. In the particle portion, benzo(k)fluoranthene and benzo(a)pyrene were over 69% and over 91%, respectively. The toxic equivalency quantities of benzo(k)fluoranthene and benzo(a)pyrene from NIER-9 (cold) for both Euro 5 and Euro 6 vehicles were more than five times higher than those of NIER (hot) and NEDC. In the case of NMHC speciation, formaldehyde emissions were the highest for 10–45% in all the driving cycles. Formaldehyde and benzene must be controlled in the emissions of medium-duty diesel trucks to reduce their health threats. The results of this study will aid in establishing a national emission inventory system for HAPs of mobile sources in Korea.
Highlights
Air pollution caused by various transportation sources poses a serious threat to human health
A total of ten medium-duty diesel trucks, five each conforming to Euro 6 and Euro 5, were selected based on data of their market share derived from the statistics of registered vehicles obtained from the Korea Automobile Manufacturers Association [25] to investigate the characteristics of their emissions in terms of regulated pollutants and hazardous air pollutants (HAPs)
The results of the tests conducted in various test cycles (WLTC, new European driving cycle (NEDC), constant volume sampler (CVS)-75, and National Institute of Environment Research (NIER)-9) using a chassis dynamometer for medium-duty diesel trucks are presented in emissions were the highest in the NEDC
Summary
Air pollution caused by various transportation sources poses a serious threat to human health. The Seoul Metropolitan Area (SMA) is significantly affected by mobile sources of pollution as the number of registered vehicles in the region is more than ten million as of 2019 [1]. The SMA is a metropolitan area composed of Seoul in its center, the Gyeonggi Province, and Incheon, and the contribution of automobiles to air pollution is high in this region. According to the national air pollutant emissions [2] data for 2017, medium-duty trucks are a major source of emissions as they contribute high proportions of CO (37.4%), NOx (25.1%), and PM2.5 (19.9%) in the SMA. Even though many studies on emissions from heavy-duty trucks have been conducted, domestic and overseas studies on emissions from medium-duty trucks are insufficient
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