Emission factors of black carbon and co-pollutants from diesel vehicles in Mexico City

Emission factors of black carbon and co-pollutants from diesel vehicles in Mexico City

M. Zavala, L. T. Molina, T. I. Yacovitch, E. C. Fortner, J. R. Roscioli, C. Floerchinger, S. C. Herndon, C. E. Kolb, W. B. Knighton, V. H. Paramo, S. Zirath, J. A. Mejía, A. Jazcilevich

Diesel-powered vehicles are intensively used in urban areas for transportinggoods and people but can substantially contribute to high emissions of blackcarbon (BC), organic carbon (OC), and other gaseous pollutants. Strategiesaimed at controlling mobile emissions sources thus have the potential toimprove air quality and help mitigate the impacts of air pollutants onclimate, ecosystems, and human health. However, in developing countries thereare limited data on the BC and OC emission characteristics of diesel-poweredvehicles, and thus there are large uncertainties in the estimation of theemission contributions from these sources. We measured BC, OC, and otherinorganic components of fine particulate matter (PM), as well as carbonmonoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2), ethane,acetylene, benzene, toluene, and C2-benzenes under real-world drivingconditions for 20 diesel-powered vehicles encompassing multiple emission leveltechnologies in Mexico City with the chasing technique using the Aerodynemobile laboratory. Average BC emission factors ranged from0.41–2.48 g kg−1 of fuel depending on vehicle type. The vehicles werealso simultaneously measured using the cross-road remote sensing technique toobtain the emission factors of nitrogen oxide (NO), CO, total hydrocarbons,and fine PM, thus allowing for the intercomparison of the results from the twotechniques. There is overall good agreement between the two techniques andboth can identify high and low emitters, but substantial differences werefound in some of the vehicles, probably due to the ability of the chasingtechnique to capture a larger diversity of driving conditions in comparisonto the remote sensing technique. A comparison of the results with the US EPAMOVES2014b model showed that the model underestimates CO, OC, and selectedVOC species, whereas there is better agreement for NOx and BC. LargerOC / BC ratios were found in comparison to ratios measured in Californiausing the same technique, further demonstrating the need for usinglocally obtained diesel-powered vehicle emission factor database indeveloping countries in order to reduce the uncertainty in the emissionsestimates and to improve the evaluation of the effectiveness of emissionsreduction measures.

2017

10.5194/acp-17-15293-2017

Atmospheric Chemistry and Physics

Copernicus Publications

Chemistry, Physics