Determination of real-world emission factors of trace metals, EC, OC, BTEX, and semivolatile organic compounds (PAHs, PCBs and PCNs) in a rural tunnel in Bilecik, Turkey

Abstract

A field study was performed in a rural tunnel to determine pollutant concentrations, sources and on road vehicle emission factors (EFs) of particulate matter, trace metals, elemental carbon (EC), organic carbon (OC), benzene, toluene, ethyl benzene and xylenes (BTEX), and polycyclic aromatic hydrocarbons (PAHs). Emission factors (EFs) for polychlorinated naphthalenes (PCNs) and polychlorinated biphenyls (PCBs) were also determined. A 12-day extensive sampling campaign during morning and afternoon periods at inlet and exit stations of the tunnel was conducted. Morphology of the particles was also investigated by Scanning Electron Microcopy (SEM). Correlation analysis, factor analysis and diagnostic PAH ratios were utilized to identify emission sources of trace metals. Identified sources include brake wear (33%), resuspension of road dust (15%), tyre wear (12%), exhaust emissions (10%), and lubricants (9%). Based on the PAH diagnostic ratios, major sources of PAHs were estimated as diesel emissions.EFs were comparable with the literature and varied from 31.5 to 295.4 mg vehicle−1 km−1 with an average of 129.2 ± 80 mg vehicle−1 km−1 for PM2.5. PM2.5–10 EFs varied between 15.9 and 236.1 mg vehicle−1 km−1 with an average of 96 ± 30 mg vehicle−1 km−1. Average EC EFs were 40.3 ± 9.8 mg vehicle−1 km−1 for PM2.5 samples and 19.5 ± 0.5 mg vehicle−1 km−1 for PM2.5–10 samples while OC EFs were 33.7 ± 18 and 15.5 ± 8.4 mg vehicle−1 km−1 for fine and coarse particles, respectively. EFs of elements were generally 2 (Al) to 59 (Mg) times higher than those previously reported in the literature. Compared to literature, relatively higher EFs for Σ13PAHs (range: 48.1–168 μg vehicle−1 km−1, average: 84.3 ± 46.4 μg vehicle−1 km−1) were obtained. BTEX emission factors were in the range of 4.2 ± 4.7 mg vehicle−1 km−1 (m + p-xylene) and 16.7 ± 10.5 mg vehicle−1 km−1 (toluene). Average EFs for ΣPCBs and ΣPCNs were 12.06 ± 5.3 μg vehicle−1 km−1 and 88.9 ± 70.4 ng vehicle−1 km−1, respectively.