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Seasonal and Diurnal Trends in Black Carbon Properties and Co-pollutants in Mexico City : Volume 15, Issue 16 (28/08/2015)

By Retama, A.

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Book Id: WPLBN0003976284
Format Type: PDF Article :
File Size: Pages 17
Reproduction Date: 2015

Title: Seasonal and Diurnal Trends in Black Carbon Properties and Co-pollutants in Mexico City : Volume 15, Issue 16 (28/08/2015)  
Author: Retama, A.
Volume: Vol. 15, Issue 16
Language: English
Subject: Science, Atmospheric, Chemistry
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Historic
Publication Date:
2015
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

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Baumgardner, D., Raga, G. B., Walker, J. W., Retama, A., & Mcmeeking, G. R. (2015). Seasonal and Diurnal Trends in Black Carbon Properties and Co-pollutants in Mexico City : Volume 15, Issue 16 (28/08/2015). Retrieved from http://ebooklibrary.org/


Description
Description: Dirección de Monitoreo Atmosférico, Secretaría del Medio Ambiente, Mexico City, Mexico. The Mexico City metropolitan area (MCMA) is a region that continues to grow in population and vehicular traffic as well as being the largest source of short-lived climate pollutants (SLCP) in Latin America. The local city government has made significant progress in controlling some of these pollutants, i.e., ozone (O3) and carbon monoxide (CO), but particulate matter (PM2.5 and PM10) and black carbon (BC) have shown a less positive response to mitigation strategies that have been in place for almost 3 decades. For the first time, extended measurements of equivalent black carbon (eBC), derived from light absorption measurements, have been made using a Photoacoustic Extinctiometer (PAX) over a 13 month period from March 2013 through March 2014. The daily trends in workdays (Monday through Saturday) and Sunday eBC, PM2.5 and the co-pollutants CO, O3 and NOx are evaluated with respect to the three primary seasons in the MCMA: rainy, cold and dry and warm and dry.

The maximum values in all of the particle and gas concentrations were significantly larger (Student's t test, P < 0.05) during the dry periods than in the rainy season. The changes from rainy to dry seasons for eBC, PM2.5, CO, O3 and NOx were 8.8 to 13.1 μg m−3 (40 %), 49 to 73 μg m−3 (40 %), 2.5 to 3.8 ppm (40 %), 73 to 100 ppb (30 %) and 144 to 252 ppb (53 %), respectively.

The primary factors that lead to these large changes between the wet and dry seasons are the accelerated vertical mixing of boundary layer and free tropospheric air by the formation of clouds that dilutes the concentration of the SLCPs, the decreased actinic flux that reduces the production of ozone by photochemical reactions and the heavy, almost daily rain that removes particulate matter.

A significant weekend effect was also identified, particularly the decrease in BC due to fewer large transport vehicles that are fueled by diesel, which produces a large fraction of the BC. The other co-pollutant concentrations are also significantly less on weekends except for O3 that shows no change in maximum values from workdays to Sundays. This lack of change is a result of the balancing effects of lower precursor gases, i.e., VOCs, offset by lower concentrations of NOx, that is an O3 inhibitor.

A comparison of the average maximum value of eBC measured during the 1 year period of the current study, with maximum values measured in shorter field campaigns in 2000 and 2006, shows no significant change in the eBC emissions over a 14 year period. This suggests that new methods may need to be developed that can decrease potentially toxic levels of this particulate pollutant.


Summary
Seasonal and diurnal trends in black carbon properties and co-pollutants in Mexico City

Excerpt
Arnott, W. P, Moosmüller, H., and Walker, J. W.: Nitrogen Dioxide and Kerosene-Fla.me Soot Calibration of Photoacoustic Instruments for Measurement of Light Absorption by Aerosols, Rev. Sci. Instrum., 71, 4545–4552, 2000.; Arnott, W. P., Hamasha K., Moosmüller, H., Sheridan P. J., and Ogren J. A.: Towards Aerosol Light-Absorption Measurements with a 7-Wavelength Aethalometer: Evaluation with a Photoacoustic Instrument and 3-Wavelength Nephelometer, Aerosol Sci. Tech., 39, 17–29, 2005.; Arnott, W. P., Walker, J. W., Moosmüller, H., Elleman, R. A., Jonsson, H. H., Buzorius, G., Conant, W. C., Flagan, R. C., and Seinfeld, J. H.: Photoacoustic insight for aerosol light absorption aloft from meteorological aircraft and comparison with particle soot absorption photometer measurements: DOE Southern Great Plains climate research facility and coastal stratocumulus imposed perturbation experiments, J. Geophys. Res.-Atmos., 111, D05S02, doi:10.1029/2005JD005964, 2006.; Baron, P. A. and Willeke, K.: Aerosol Measurements Principles, Techniques and Applications, John Wiley and Sons, New York, NY, 1133 pp., 2001.; Barth, M. C. and Church, A. T.: Regional and global distributions and lifetimes of sulfate aerosols from Mexico City and southeast China, J. Geophy. Res, 104, 30231–30239. 1999.; Baumgardner, D., Raga, G. B., Kok, G., Ogren, J., Rosas, I., Baez, A., and Novakov, T.: On the Evolution of Aerosol Properties at a Mountain Site Above Mexico City, J. Geophys. Res., 105, 22243–22253, 2000.; Baumgardner, D., Raga, G., Peralta, O., Rosas, I., Castro, T., Kuhlbusch, T., John, A., and Petzold, A.: Diagnosing black carbon trends in large urban areas using carbon monoxide measurements, J. Geophys. Res., 107, 8342, doi:10.1029/2001JD000626, 2002.; Baumgardner, D., Raga, G. B., and Muhlia, A.: Evidence for the formation of CCN by photochemical processes in Mexico City, Atmos. Environ., 38, 357–367, 2004.; Baumgardner, D., Kok, G. L., and Raga, G. B.: On the diurnal variability of particle properties related to light absorbing carbon in Mexico City, Atmos. Chem. Phys., 7, 2517–2526, doi:10.5194/acp-7-2517-2007, 2007.; Jáuregui, E.: Mesomicroclima de la Ciudad de México, Instituto de Geografía, UNAM, 87 pp., 1971.; Baumgardner, D., Grutter, M., Allan, J., Ochoa, C., Rappenglueck, B., Russell, L. M., and Arnott, P.: Physical and chemical properties of the regional mixed layer of Mexico's Megapolis, Atmos. Chem. Phys., 9, 5711–5727, doi:10.5194/acp-9-5711-2009, 2009.; Bond, T. C., Habib, G., and Bergstrom, R. W.: Limitations in the enhancement of visible light absorption due to mixing state, J. Geophys. Res., 111, 211, doi:10.1029/2006JD007315, 2006.; Bond, T. C., Doherty, S. J., Fahey, D. W., Forster, P. M., Berntsen, T., DeAngelo, B. J., Flanner, M. G., Ghan, S., Kärcher, B., Koch, D., Kinne, S., Kondo, Y., Quinn, P. K., Sarofim, M. C., Schultz, M. G., Schulz, M., Venkataraman, C., Zhang, H., Zhang, S., Bellouin, N., Guttikunda, S. K., Hopke, P. K., Jacobson, M. Z., Kaiser, J. W., Klimont, Z., Lohmann, U., Schwarz, J. P., Shindell, D., Storelvmo, T., Warren, S. G., and Zender, C. S.: Bounding the role of black carbon in the climate system: A scientific assessment, J. Geophys. Res.-Atmos., 188, 5380–5552, 2013.; Bowerman, N. H. A., Frame, D. J. Huntingford, C., Lowe, J. A., Smith, S. M., and Allen, M. R.: The role of short-lived climate pollutants in meeting temperature goals, Nature Climate Change, 3, 1021–1024 , 2013.; Chan, T. W., Brook, J. R., Smallwood, G. J., and Lu, G.: Time-resolved measurements of black carbon light absorption enhancement in urban and near-urban locations of southern Ontario, Canada, Atmos. Chem. Phys., 11

 

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