Chemically-speciated on-road PM2.5 motor vehicle emission factors in Hong Kong

Department of Environmental Science and Technology, School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, No.28 Xianning West Road, Xi'an, Shaanxi, 710049, China; SKLLQG, Institute of Earth and Environment, CAS, Xi'an, Shaanxi, 710075, China; Department of Civil and Structural Engineering, Research Center for Environmental Technology and Management, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China; Division of Atmospheric Sciences, Desert Research Institute, Reno, Nevada, USA; Hong Kong Environmental Protection Department, 47/F, Revenue Tower, 5 Gloucester Road, Wan Chai, Hong Kong, China
Science of The Total Environment (Impact Factor: 3.26). 03/2010; 408(7):1621-1627. DOI: 10.1016/j.scitotenv.2009.11.061
Source: PubMed

ABSTRACT PM2.5 (particle with an aerodynamic diameter less than 2.5 µm) was measured in different microenvironments of Hong Kong (including one urban tunnel, one Hong Kong/Mainland boundary roadside site, two urban roadside sites, and one urban ambient site) in 2003. The concentrations of organic carbon (OC), elemental carbon (EC), water-soluble ions, and up to 40 elements (Na to U) were determined. The average PM2.5 mass concentrations were 229 ± 90, 129 ± 95, 69 ± 12, 49 ± 18 µg m− 3 in the urban tunnel, cross boundary roadside, urban roadside, and urban ambient environments, respectively. Carbonaceous particles (sum of organic material [OM] and EC) were the dominant constituents, on average, accounting for ∼ 82% of PM2.5 emissions in the tunnel, ∼ 70% at the three roadside sites, and ∼ 48% at the ambient site, respectively. The OC/EC ratios were 0.6 ± 0.2 and 0.8 ± 0.1 at the tunnel and roadside sites, respectively, suggesting carbonaceous aerosols were mainly from vehicle exhausts. Higher OC/EC ratio (1.9 ± 0.7) occurred at the ambient site, indicating contributions from secondary organic aerosols. The PM2.5 emission factor for on-road diesel-fueled vehicles in the urban area of Hong Kong was 257 ± 31 mg veh− 1 km− 1, with a composition of ∼ 51% EC, ∼ 26% OC, and ∼ 9% SO4=. The other inorganic ions and elements made up ∼ 11% of the total PM2.5 emissions. OC composed the largest fraction (∼ 51%) in gasoline and liquid petroleum gas (LPG) emissions, followed by EC (∼ 19%). Diesel engines showed higher emission rates than did gasoline and LPG engines for most pollutants, except for V, Br, Sb, and Ba.

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