Source apportionment of gaseous and particulate PAHs from traffic emission using tunnel measurements in Shanghai, China

Ying Liu,Siyao Wang,Rainer Lohmann,Na Yu,Chenkai Zhang,Yi Gao,Jianfu Zhao,Limin Ma

doi:10.1016/j.atmosenv.2015.02.041

Abstract

Understanding sources and contributions of gaseous and particulate PAHs from traffic-related pollution can provide valuable information for alleviating air contamination from traffic in urban areas. On-road sampling campaigns were comprehensively conducted during 2011–2012 in an urban tunnel of Shanghai, China. 2–3 rings PAHs were abundant in the tunnel's gas and particle phases. Diagnostic ratios of PAHs were statistically described; several were significantly different between the gas and particle phases. Principal component analysis (PCA), positive matrix factorization (PMF), bivariate correlation analysis and multiple linear regression analysis (MLRA) were applied to apportion sources of gaseous and particulate PAHs in the tunnel. Main sources of the gaseous PAHs included evaporative emission of fuel, high-temperature and low-temperature combustion of fuel, accounting for 50–51%, 30–36% and 13–20%, respectively. Unburned fuel particles (56.4–78.3%), high-temperature combustion of fuel (9.5–26.1%) and gas-to-particle condensation (12.2–17.5%) were major contributors to the particulate PAHs. The result reflected, to a large extent, PAH emissions from the urban traffic of Shanghai. Improving fuel efficiency of local vehicles will greatly reduce contribution of traffic emission to atmospheric PAHs in urban areas. Source apportionment of PM10 mass was also performed based on the organic component data. The results showed that high-temperature combustion of fuel and gas-to-particle condensation contributed to 15–18% and 7–8% of PM10 mass, respectively, but 55–57% of the particle mass was left unexplained. Although the results from the PCA and PMF models were comparable, the PMF method is recommended for source apportionment of PAHs in real traffic conditions. In addition, the combination of multivariate statistical method and bivariate correlation analysis is a useful tool to comprehensively assess sources of PAHs.

Highlights

2-3 rings Polycyclic aromatic hydrocarbons (PAHs) are abundant and dominated by parent and alkylated naphthalene in the gas phase, while they are abundant in the particle phase
Many studies suggested diesel-vehicular or heavy-duty vehicle emission were enriched in the low molecular weight PAH (≤4 rings), whereas, the high molecular weight PAH were more abundant in gasoline engine or light-duty vehicle emission (Ancelet et al, 2011; El Haddad et al, 2009; Kam et al, 2012)
In the urban tunnel of Shanghai, 2-3 rings PAHs were abundant in the gas and particle phases

Summary

Introduction

Understanding sources and contributions of gaseous and particulate PAHs from traffic-related pollution can provide valuable information for alleviating air contamination from traffic in urban areas. 2-3 rings PAHs were abundant in the tunnel’s gas and particle phases. Diagnostic ratios of PAHs were statistically described; several were significantly different between the gas and particle phases. Main sources of the gaseous PAHs included evaporative emission of fuel, high-temperature and low-temperature combustion of fuel, accounting for 50-51%, 30-36% and 13-20%, respectively. Unburned fuel particles (56.4-78.3%), high-temperature combustion of fuel (9.5-26.1%) and gas-to-particle condensation (12.2-17.5%) were major contributors to the particulate PAHs. The

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Results

Conclusion