Vehicular emission of volatile organic compounds (VOCs) from a tunnel study in Hong Kong

K F Ho,Y S Li,S S H Ho,S C Lee,W K Ho,D R Blake,K Fung,Y Cheng,P K K Louie,D Park

doi:10.5194/acp-9-7491-2009

Abstract

Abstract. Vehicle emissions of volatile organic compounds (VOCs) were determined at the Shing Mun Tunnel, Hong Kong in summer and winter of 2003. One hundred and ten VOCs were quantified in this study. The average concentration of the total measured VOCs at the inlet and outlet of the tunnel were 81 250 pptv and 117 850 pptv, respectively. Among the 110 compounds, ethene, ethyne and toluene were the most abundant species in the tunnel. The total measured VOC emission factors ranged from 67 mg veh−1 km−1 to 148 mg veh−1 km−1, with an average of 115 mg veh−1 km−1. The five most abundant VOCs observed in the tunnel were, in decreasing order, ethene, toluene, n-butane, propane and i-pentane. These five most abundant species contributed over 38% of the total measured VOCs emitted. The high propane and n-butane emissions were found to be associated with liquefied petroleum gas (LPG)-fueled taxis. Fair correlations were observed between marker species (ethene, i-pentane, n-nonane, and benzene, toluene, ethylbenzene and xylenes – BTEX) with fractions of gasoline-fueled or diesel-fueled vehicles. Moreover, ethene, ethyne, and propene are the key species that were abundant in the tunnel but not in gasoline vapors or LPG. The ozone formation potential from the VOCs in Hong Kong was evaluated by the maximum increment reactivity (MIR). It was found to be 568 mg of ozone per vehicle per kilometer traveled. Among them, ethene, propene and toluene contribute most to the ozone-formation reactivity.

Highlights

Vehicular emissions are one of major sources of volatile organic compounds (VOCs) in the urban areas throughout the Pearl River Delta Region in China
The average emission factor was 0.8 mg veh−1 km−1 which is higher than previous study done by chassis dynamometer (Fried et al, 1992)
VOCs is 115 mg veh−1 km−1) which is similar to the results of Taipei tunnel, of 427 g (Hwa et al, 2002)

Summary

Introduction

Vehicular emissions are one of major sources of volatile organic compounds (VOCs) in the urban areas throughout the Pearl River Delta Region in China. VOCs play an important role in the formation of ground-level O3 and photochemical oxidants associated with urban smog (Monod et al, 2001). Smog is a mixture of secondary pollutants such as O3, nitrogen dioxide (NO2), nitric acid (HNO3), aldehydes and other organic compounds, formed from photochemical reactions between nitrogen oxides (NOx) and hydrocarbons. There are two widely used methods to determine vehicular emission profiles: chassis dynamometer tests and direct measurements in roadway tunnels. These two types of measurements strongly vary with many factors, such as vehicular engine types (e.g. gasoline fueled and diesel fueled engines)

Methods

Results

Conclusion