AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Changes in Emissions Rates and Exposure of PM2.5, eBC, and UFP Attributable to the Renewal of a Bus Rapid Transit System Fleet
DANIELA MENDEZ, Sebastian Espitia, Andres Felipe Rosero, Boris Galvis, Ricardo Morales Betancourt, Universidad de los Andes
Abstract Number: 757 Working Group: Aerosol Exposure
Abstract Transportation activities in urban centers are strongly associated with increased personal exposure to air pollutants. This situation can be exacerbated in developing economies due to older vehicle fleets and less stringent emission standards. In this work we focus on the Bus Rapid Transit System (BRT) of the city of Bogotá, in Colombia. This system is one of the largest in the world, with nearly 2.4 million trips daily. Previous work developed by the researchers has demonstrated that in-cabin concentration of PM2.5, Black Carbon (BC), and ultra-fine particles (UFP) are alarmingly high inside the BRT buses and stations (Morales et. al., 2017; 2019). However, starting in July 2019, a new bus fleet will replace nearly 1400 18-year-old diesel-powered buses that are part of the current BRT system. The new fleet includes both EURO-VI natural-gas and EURO-V DPF-equipped diesel-powered buses. This fleet renewal is expected to significantly reduce emission rates of BC, PM2.5, and UFP. We aim to characterize the evolution of BC, PM2.5, and UFP fuel- based emission rates during the fleet renewal and to quantify the net change in exposure within the BRT system before and after the intervention. We selected seven points distributed throughout the BRT system to determine fuel-based emission factors by applying the carbon balance method. Carbon dioxide concentration was measured at 1 Hz with a NDIR sensor (LI-COR 830). UFP particles were measured using, both, an electric low-pressure impactor (Dekati, DMM-230) and a diffusion size classifier (DiSCmini). Aethalometers and laser scattering devices were used to measure BC and PM2.5 respectively. Video recording was used to register all the events. Image analysis software was used to determine the timing of the passing of a BRT bus and its license plate. This information was compared to a data base of fuel type, mileage, and nominal emission standard. A total of 85 emission factors were calculated, obtaining an average of 2.01 mg PM2.5/kg-fuel, 0.79 mg BC/kg-fuel and 1.49×1015 UFP/kg-fuel. Simultaneously, travelers in the system carrying portable measuring devices (micro-Aethalometers, DustTrack, and electrochemical cell CO sensors) performed natural trips in the system to determine the exposure concentrations. Our baseline phase results confirm the extreme exposure of the users of the current fleet, and highlights the large emission rates observed in these vehicles. It is expected to see a substantial positive change in the reduction of emissions and exposure with the implementation of the new fleet, and those measurements will be performed during the months of July and August.