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37.
Particulate Phase Levels of PAH’s, Organic and Elemental
Carbon at two sites in Mexico City.
Diana
Guzman-Torres (1, 2), Maricela Maubert (1),
Arantzazu Eiguren-Fernandez (2), Antonio H. Miguel (2),
and Pablo Cicero-Fernandez (3).
(1)
Autonomous Metropolitan University (UAM), Mexico City
(2)
Southern California Particle Center and Supersite,
Institute of the Environment, University of California, Los Angeles
(3)
Department of Environmental Health Sciences,
University of California, Los Angeles
Mexico City is one of the most polluted cities in the world.
This research studied the diurnal and nocturnal variation on
the concentration of Polycyclic Aromatic Hydrocarbons (PAHs),
Elemental Carbon (EC) and Organic Carbon (OC); present in PM10
of two sites located in Mexico City. The first samplers were
located closer to a high vehicular traffic area, at La Merced
Junior-High School, the other at a residential area with a comparatively
small vehicular traffic, located at Pedregal Elementary School.
This site is located downwind of La Merced during daylight hours.
The sampling campaign was carried out with the collaboration
of the Mexico City Environmental Secretary (RAMA.), who provided
meteorological data. In addition, they provided three PM10 High
Volume samplers for the study.
The main objectives were: 1) to get atmospheric
samples from two different sites in Mexico City located near a
source and a receptor area; 2) to measure PAHs, EC and OC from
PM10 samples collected in 8-hr time bins, continuously for one
week at each site; 3) to extract and quantify the 16 priority
US EPA priority PAHs using GC/MS; 4) to correlate the meteorological
parameters with the target species concentrations; and 5) to identify
secondary organic aerosol formation at the sites.
The preliminary results of the more toxic PAHs (e.g.
benzo(a)pyrene, BaP, benzo(ghi)perylene, BgP) concentrations are
considered very high. The results imply a large number of uncontrolled
high emitter vehicles in the city and a potential high exposure
to these carcinogenic compounds by the Mexico City population.
The results also suggest that SOA is formed during atmospheric
transport which could lead to changes in the toxicity of the PM
by shifting the toxics ultrafine mode to the accumulation mode.
The effect of meteorology, especially surface inversions, appears
to be the major factor controlling the concentration of PAHs at
the source site.
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