title: Global time trends in PAH emissions from motor vehicles.
abstract: Emission from motor vehicles is the most important source of polycyclic aromatic hydrocarbons (PAHs) in urban areas. Emission factors of individual PAHs for motor vehicles reported in the literature varied 4 to 5 orders of magnitude, leading to high uncertainty in emission inventory. In this study, key factors affecting emission factors of PAHs (EFPAH) for motor vehicles were evaluated quantitatively based on thousands of EFPAHmeasured in 16 countries for over 50 years. The result was used to develop a global emission inventory of PAHs from motor vehicles. It was found that country and vehicle model year are the most important factors affecting EFPAH, which can be quantified using a monovariate regression model with per capita gross domestic production (purchasing power parity) as a sole independent variable. On average, 29% of variation in log-transformed EFPAHcould be explained by the model, which was equivalent to 90% reduction in overall uncertainty on arithmetic scale. The model was used to predict EFPAHand subsequently PAH emissions from motor vehicles for various countries in the world during a period from 1971 to 2030. It was estimated that the global emission reached its peak value of approximate 101 Gg in 1978 and decreased afterwards due to emission control in developed countries. The annual emission picked up again since 1990 owing to accelerated energy consumption in China and other developing countries. With more and more rigid control measures taken in the developing world, global emission of PAHs is currently passing its second peak. It was predicted that the emission would decrease from 77 Gg in 2010 to 42 Gg in 2030.
authors.affiliation: Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.
authors.forename: Huizhong
authors.initials: H
authors.lastname: Shen
authors.forename: Shu
authors.initials: S
authors.lastname: Tao
authors.forename: Rong
authors.initials: R
authors.lastname: Wang
authors.forename: Bin
authors.initials: B
authors.lastname: Wang
authors.forename: Guofeng
authors.initials: G
authors.lastname: Shen
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Shenshen
authors.initials: S
authors.lastname: Su
authors.forename: Ye
authors.initials: Y
authors.lastname: Huang
authors.forename: Xilong
authors.initials: X
authors.lastname: Wang
authors.forename: Wenxin
authors.initials: W
authors.lastname: Liu
authors.forename: Bengang
authors.initials: B
authors.lastname: Li
authors.forename: Kang
authors.initials: K
authors.lastname: Sun
keywords: Emission factor; Global inventory; Polycyclic aromatic hydrocarbons (PAHs); Time trend; Vehicle emission