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Chemically-resolved aerosol eddy covariance flux measurements in urban Mexico City during MILAGRO 2006

Zalakeviciute, R.; Alexander, M.L.; Allwine, E.; Jimenez, J.L.; Jobson, B.T.; Molina, L.T.; Nemitz, E.; Pressley, S.N.; VanReken, T.; Ulbrich, I.M.; Velasco, E.; Lamb, B.K.. 2012 Chemically-resolved aerosol eddy covariance flux measurements in urban Mexico City during MILAGRO 2006. Atmospheric Chemistry and Physics, 12 (16). 7809-7823. 10.5194/acp-12-7809-2012

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Abstract/Summary

As part of the MILAGRO 2006 field campaign, the exchange of atmospheric aerosols with the urban landscape was measured from a tall tower erected in a heavily populated neighborhood of Mexico City. Urban submicron aerosol fluxes were measured using an eddy covariance method with a quadrupole aerosol mass spectrometer during a two week period in March, 2006. Nitrate and ammonium aerosol concentrations were elevated at this location near the city center compared to measurements at other urban sites. Significant downward fluxes of nitrate aerosol, averaging −0.2 μg m−2 s−1, were measured during daytime. The urban surface was not a significant source of sulfate aerosols. The measurements also showed that primary organic aerosol fluxes, approximated by hydrocarbon-like organic aerosols (HOA), displayed diurnal patterns similar to CO2 fluxes and anthropogenic urban activities. Overall, 47% of submicron organic aerosol emissions were HOA, 35% were oxygenated (OOA) and 18% were associated with biomass burning (BBOA). Organic aerosol fluxes were bi-directional, but on average HOA fluxes were 0.1 μg m−2 s−1, OOA fluxes were −0.03 μg m−2 s−1, and BBOA fluxes were −0.03 μg m−2 s−1. After accounting for size differences (PM1 vs PM2.5) and using an estimate of the black carbon component, comparison of the flux measurements with the 2006 gridded emissions inventory of Mexico City, showed that the daily-averaged total PM emission rates were essentially identical for the emission inventory and the flux measurements. However, the emission inventory included dust and metal particulate contributions, which were not included in the flux measurements. As a result, it appears that the inventory underestimates overall PM emissions for this location.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.5194/acp-12-7809-2012
Programmes: CEH Topics & Objectives 2009 - 2012 > Biogeochemistry > BGC Topic 1 - Monitoring and Interpretation of Biogeochemical and Climate Changes > BGC - 1.1 - Monitor concentrations, fluxes, physico-chemical forms of current and emerging pollutants ...
CEH Sections: Billett (to November 2013)
ISSN: 1680-7316
Additional Information. Not used in RCUK Gateway to Research.: This is an open-access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
NORA Subject Terms: Atmospheric Sciences
Date made live: 13 Sep 2012 08:57
URI: http://nora.nerc.ac.uk/id/eprint/19517

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