Evaluating Nitrogen Oxides and Ultrafine Particulate Matter Emission Features of Urban Bus Based on Real-World Driving Conditions in the Yangtze River Delta Area, China

Dengguo Liu,Liang Fang,Juan Liu,Weiming Huang,Diming Lou

doi:10.3390/su10062051

Dengguo Liu, Liang Fang + Show 3 more

Open Access

https://doi.org/10.3390/su10062051

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Abstract

A Portable Emission Measurement System was used in this study to evaluate the exhaust emission characteristics of nitrogen oxides (NOx), ultrafine particulate matter (PM), and ultrafine particulate number (PN) from buses in the Yangtze River Delta, China. Results showed that NOx emission factor (unit: g·km−1) increased from 5.0 to 19.1, and PM emission factor (unit: g·km−1) increased from 0.001 to 0.189. A nonlinear model was established based on scientific statistical method, which showed that NOx and PM emission factors significantly decreased with speed increasing. The model also showed a “long tail effect” of NOx and PM emission factors beyond 30 km·h−1. Furthermore, hybrid bus exhausted less NOx, PM, and PN emissions compared to conventional bus in the acceleration condition. Exhaust rates of NOx, PM and PN emissions (unit: g·s−1) increased with speed increasing under steady state driving condition, while PN emissions commonly showed a unimodal distribution at the speed of 20 km·h−1.

Highlights

Previous research showed traffic induced emissions are important contributors to the urban emission inventory [1,2]
Recent study in Shanghai concluded Nitrogen Oxides (NOx) from mobile source emissions is responsible for about 37.6% of total emission and 45% of Particulate Matter (PM) in its central areas
The instrument was mainly composed of a host, a power control unit (PCU), an external signal input unit (EIU), Pitot tube flowmeter, sensors and computer

Summary

Introduction

Previous research showed traffic induced emissions are important contributors to the urban emission inventory [1,2]. Recent study in Shanghai concluded Nitrogen Oxides (NOx) from mobile source emissions is responsible for about 37.6% of total emission and 45% of Particulate Matter (PM) in its central areas. Recent studies show that particulate number (PN) is more harmful to human health, compared to PM mass [3]. Hydrocarbons (HC) and NOx in the vehicle exhaust gas can actively form ozone (O3) via photochemical reaction causing secondary air pollution problem. Urban bus has unique operational characteristics due to their specific driving conditions with much more frequent starting, braking, idling, and low-speed driving time compared with passenger cars due to the bus stops and signal intersections

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