Overestimation of on-road air quality surveying data measured with a mobile laboratory caused by exhaust plumes of a vehicle ahead in dense traffic areas.
The unintended influence of exhaust plumes emitted from a vehicle ahead to on-road air quality surveying data measured with a mobile laboratory (ML) at 20-40 km h-1in dense traffic areas was investigated by experiment and life-sized computational fluidic dynamics (CFD) simulation. The ML equipped with variable sampling inlets of five columns by four rows was used to measure the spatial distribution of CO2and NOxconcentrations when following 5-20 m behind a sport utility vehicle (SUV) as an emitter vehicle equipped with a portable emission monitoring system (PEMS). The PEMS measured exhaust gases at the tailpipe for input data of the CFD simulations. After the CFD method was verified with experimental results of the SUV, dispersion of exhaust plumes emitted from a bus and a sedan was numerically analyzed. More dilution of the exhaust plume was observed at higher vehicle speeds, probably because of eddy diffusion that was proportional to turbulent kinetic energy and vehicle speed. The CO2and NOxconcentrations behind the emitter vehicle showed less overestimation as both the distance between the two vehicles and their background concentrations increased. If the height of the ML inlet is lower than 2 m and the ML travels within 20 m behind a SUV and a sedan ahead at 20 km h-1, the overestimation should be considered by as much as 200 ppb in NOxand 80 ppm in CO2. Following a bus should be avoided if possible, because effect of exhaust plumes from a bus ahead could not be negligible even when the distance between the bus and the ML with the inlet height of 2 m, was more than 40 m. Recommendations are provided to avoid the unintended influence of exhaust plumes from vehicles ahead of the ML during on-road measurement in urban dense traffic conditions.
Center for Environment, Health and Welfare Research, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea; Department of Mechanical Engineering, Hanyang University, Wangsimni-ro 222, Seongdong-gu, Seoul 04763, Republic of Korea.
Sang-Hee
SH
Woo
School of Natural Resources and Environmental Science, Kangwon National University, Kangwondaehak-gil 1, Chuncheon-si, Gangwon-do 24341, Republic of Korea.
Kyung-Hwan
KH
Kwak
Center for Environment, Health and Welfare Research, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea.
Gwi-Nam
GN
Bae
Center for Environment, Health and Welfare Research, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea.
Kyung Hwan
KH
Kim
Center for Environment, Health and Welfare Research, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea.
Chang Hyeok
CH
Kim
Department of Mechanical Engineering, Hanyang University, Wangsimni-ro 222, Seongdong-gu, Seoul 04763, Republic of Korea.
Se-Jin
SJ
Yook
Transportation Pollution Research Center, National Institute of Environmental Research, Hwangyeong-ro 42, Seo-gu, Incheon 22755, Republic of Korea.
Sangzin
S
Jeon
Transportation Pollution Research Center, National Institute of Environmental Research, Hwangyeong-ro 42, Seo-gu, Incheon 22755, Republic of Korea.
Sangil
S
Kwon
Transportation Pollution Research Center, National Institute of Environmental Research, Hwangyeong-ro 42, Seo-gu, Incheon 22755, Republic of Korea.
Jeongsoo
J
Kim
Center for Environment, Health and Welfare Research, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea. Electronic address: sblee2@kist.re.kr.
Seung-Bok
SB
Lee
D000393:Air Pollutants / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods* / Q000592:standards; D006801:Humans; D018986:Motor Vehicles; D015203:Reproducibility of Results; D001335:Vehicle Emissions / Q000032:analysis*
D000393:Air Pollutants; D001335:Vehicle Emissions
CO(2); Mobile laboratory; NO(x); On-road air pollution; Portable emission monitoring system; Vehicle exhaust plume