Emission Characteristics of VOCs from On-Road Vehicles in an Urban Tunnel in Eastern China and Predictions for 2017-2026

Automobile exhaust emissions represent the main source of atmospheric volatile organic compound (VOC) pollution in urban areas of China To accurately determine recent emission characteristics of vehicles during urban road conditions, an optimized tunnel experiment was conducted in Longchuan Tunnel, Hefei, in eastern China Based on preliminary experiments examining the spatial and temporal characteristics of VOCs within the tunnel, a sampling scheme was designed to quantitatively analyze 51 VOCs. Among the 36 detected VOCs, about 52% were alkanes (mainly branched alkanes), with a total average emission factor of 41.39 +/- 12.81 mg km(-1) veh(-1). Benzene homologues contributed the second largest proportion, and alkenes accounted for the smallest fraction. Dimethylbutane exhibited the highest average emission factor (13.3 +/- 3.19 mg km(-1) veh(-1)), followed by toluene (7.06 +/- 3.14 mg km(-1) veh(-1))and then 2-methylpentane (6.44 +/- 2.10 mg km(-1) veh(-1)). The emission factors of the VOCs in Longchuan Tunnel were consistent with those from other studies in recent years but were considerably lower than those measured in tunnels in 2004. Based on the average emission factors of VOCs for light-duty and heavy-duty vehicles (81 +/- 27 and 99 +/- 42 mg km(-1) veh(-1), respectively), the predicted vehicle population, and vehicle-kilometers-traveled data, the emissions of VOCs were predicted for 2017-2026. The results show that if no control measures are taken, the total VOC emission volume and emission intensity will increase from 2510 +/- 850 tons yr(-1) to 3270 +/- 1120 tons yr(-1) and from 1859 +/- 630 kg km(-2) to 2422 +/- 830 kg km(2), respectively, between 2017 and 2026.