Characterization of Exhaust CO, HC and NOx Emissions from Light-Duty Vehicles under Real Driving Conditions

Hui Mei,Yunjing Wang,Bowen Wang,Lulu Wang,Yi Li,Rencheng Zhu,Menglei Wang,Xiaofeng Bao,Ruiqin Zhang

doi:10.3390/atmos12091125

Abstract

On-road exhaust emissions from light-duty vehicles are greatly influenced by driving conditions. In this study, two light-duty passenger cars (LDPCs) and three light-duty diesel trucks (LDDTs) were tested to investigate the on-road emission factors (EFs) with a portable emission measurement system. Emission characteristics of carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) emitted from vehicles at different speeds, accelerations and vehicle specific power (VSP) were analyzed. The results demonstrated that road conditions have significant impacts on regulated gaseous emissions. CO, NOx, and HC emissions from light-duty vehicles on urban roads increased by 1.1–1.5, 1.2–1.4, and 1.9–2.6 times compared with those on suburban and highway roads, respectively. There was a rough positive relationship between transient CO, NOx, and HC emission rates and vehicle speeds, while the EFs decreased significantly with the speed decrease when speed ≤ 20 km/h. The emissions rates of NOx and HC tended to increase and then decrease as the acceleration increased and the peak occurred at 0 m/s2 without considering idling conditions. For HC and CO, the emission rates were low and changed gently with VSP when VSP < 0, while emission rates increased gradually with the VSP increase when VSP > 0. For NOx NOx emission rates were lower and had no obvious change when VSP < 0. However, NOx emissions were positively correlated with VSP, when VSP > 0.

Highlights

Introduction published maps and institutional affilIt is widely known that motor vehicle exhaust emissions have become a major anthropogenic source of urban atmospheric pollution with the explosive growth of vehicle population, especially in the metropolitan cities in China [1,2]
There was a trend that the average emission factors of carbon monoxide (CO), nitrogen oxide (NOx) and HC under urban road conditions were slightly higher than the ones for suburban and highways
CO emissions of light-duty passenger cars (LDPCs) on suburban and highway decreased by 18.0% and 31.5%, respectively, compared with urban roads; NOx emissions was reduced by 18.4% and 22.1%; and the reduction of HC was even greater, reaching 46.6%

Summary

Introduction

It is widely known that motor vehicle exhaust emissions have become a major anthropogenic source of urban atmospheric pollution with the explosive growth of vehicle population, especially in the metropolitan cities in China [1,2]. China has been the world’s largest automobile manufacturer and seller for twelve consecutive years since 2009 [3]. By the end of 2020, the number of automobiles in China has reached 281 million, which is basically equivalent to the United States [4]. Ministry of Ecological Environment (MEE) showed that the total motor vehicle exhaust emissions of carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) were. To identify the characteristics of vehicular emissions, various test methods were adopted in previous studies.

Methods

Results

Conclusion