[Characteristics of Particulate and Inorganic Elements of Motor Vehicles Based on a Tunnel Environment]

Respirable particulate matter(PM_2.5)samples were collected at different locations (inside and outside the tunnel) at the Zhang Zizhong Tunnel in Tianjin in September 2015. Seventeen inorganic elements were measured, and the sources were analyzed by the PCA receptor model. The results show that the daily average concentration of PM_2.5 inside and outside the tunnel is (94.79±62.78) μg·m^-3 and (83.92±61.60) μg·m^-3, respectively. The concentration during the working day is higher than on a non-working day, and, to a certain extent, PM_2.5 concentration in the tunnel during peak periods is correlated with the vehicle flow, which indicates that PM_2.5 concentration is affected by motor vehicle pollution seriously. In the tunnel, the concentrations of Si, Fe, Al, Ca, and Mg are higher, the mass fraction reach 98.48% of all analyzed elements and these elements are less affected by vehicles. Fe and trace heavy metals (Zn, Cu, and Pb) are related closely to motor vehicle pollution. From the Wilcoxon Signed-Rank test, there are significant differences in Ba, Cu, Zn, Mo, Sn, and Sb inside and outside the tunnel. Enrichment factors inside and outside the tunnel show that the enrichment factor ratios of Co, Mn, Cr, Ca, Mg, Ba, Fe, Mo, and V are less than 5, which are mainly from the crust. In addition, the enrichment factor ratios of Cu, Zn, Pb, Sn, Sb, and Cd are greater than 5, which are affected largely by anthropogenic sources. The factor analysis indicates that the main pollution sources in the tunnel are the mixed sources of wear and the combustion of fuel, the dust, and the combustion of diesel vehicles. In addition, in order to analyze the source of motor vehicle pollution further, a factor analysis indicates that the main pollution sources are tire wear and exhaust emission, brake wear and exhaust emissions, and diesel emissions.