Characterizations of volatile organic compounds (VOCs) from vehicular emissions at roadside environment: The first comprehensive study in Northwestern China

Abstract

21Vehicular emission (VE) is one of the important anthropogenic sources for ground-level volatile 22 organic compounds (VOCs) in both urban and suburban areas. A first comprehensive campaign was 23 conducted at an urban roadside in Xi'an, China in summer, 2016. A total of 57 VOCs, as known as critical 24 surface ozone (O 3 ) precursors, and other trace gases were measured simultaneously during the sampling 25 period. Iso-pentane, a tracer of gasoline evaporation, was the most abundant VOC in the roadside samples, 26 followed by isobutane and benzene, attributed to the largest composition (~70%) of gasoline-fueled 27 vehicles on the road. The molar ratio of toluene/benzene (T/B) in our study (0.36) is far lower than the 28 range reported in other cities, indicating the stronger contributions from diesel emissions. The results of 29 source apportionment achieved with positive matrix factorization (PMF) receptor model were highly 30 consistent with the vehicles compositions, strongly evidenced that the precise characterization of the VE 31 sources from those marker species. The degrees of individual compound contributed to O 3 production 32 were weighed by ozone formation potential (OFP). Propylene (20%), 1-butene (11%) and 33 iso-pentane(10%) were the top three contributors at the roadside. The information of this study 34 complements the VOCs database regarding to the VE sources in Northwestern China. 35 36 Capsule: Illustrate the current composition and the major emission sources of VOCs at the roadside 38 environment in northwest China, and discuss their impacts on ozone formation.

Source Apportionment and Secondary Transformation of Atmospheric Nonmethane Hydrocarbons in Chengdu, Southwest China

“…Under atmospheric conditions, the reaction of m/p‐xylene with OH radicals is rapid; thus, the X/E ratio decreases with time (C. Huang, Wang, et al, ). When the value of the X/E ratio is approximately 3, the contribution of VOCs from local emissions is more important (B. Li, Ho, et al, ). The X/E ratio in this study showed no obvious diurnal variation (Figure S4b), with a ratio of 2.2 ± 1.2.…”

A Spatial-Temporal Resolved Validation of Source Apportionment by Measurements of Ambient VOCs in Central China

“…p is the number of source, f and g are the species profile of each source and the amount of mass contributed by each source to the sample e ij is the residual for each sample and specie [22]. The other details of PMF applied to VOC data for source profiles and the contributions of each VOC species have been introduced in previous studies [24][25][26]. In this study, 28 VOC species were input into the PMF model.…”

“…The ratios between the mixing ratios of pairs of ambient VOC species are useful indictors of the major emission sources, photochemical process and the influence of the generating functions. The ratio of ambient mixing ratios of two hydrocarbons with similar chemical reactivity are theoretically equal to those of their relative emission rates from sources [26,34]. Thus, we examined the monthly variations in several groups of VOC species ratio to reveal the typical characteristics of different emissions.…”

Control of air pollution caused by vehicular emissions

“…1. Improvement of engines is carried out to ensure the most complete combustion of fuel [21,22]. The engines based on weakest mixture, multi-valve system of redistribution, fuel injection instead of carbureted air-fuel mixture, electronic ignition.…”