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Sistema de Información Científica
Red de Revistas Científicas de América Latina y el Caribe, España y Portugal
Hourly and monthly ambient air formaldehyde variations in Mexico
city
Baez, A.P. and Belmont,
R.D.
Centro de Ciencias de la Atmósfera, UNAM,
04510
México, D.F.
Tel.
548-81-90,
Fax
548-97-81,
Formaldehyde concentrations in ambient air were measured at the
National University of Mexico, Mexkco City. Air samples were
taken as a function of time of day, from January to December of
1988.
Maximum concentrations were obtained at noon. The high
mixing ratios found at morning and early afternoon seem to
indicate a diurna1 variation in the boundary layer. The apparent
photochemical nature of H2C0 seems to favor the high
concentrations found in hours of the highest actinic fluxes, but
in Mexico City the H2C0 concentration depends in great part from
the direct emissions, and to be formed from hydrocarbon
precursors. The rapid changes in H2C0 concentrations were
probably
caused rather by transport, deposition and wet
scavenging. Small differences in monthly means were observed.
The lowest value was found in March, month characterized by
strong winds. The rainout and washout contibuted to deplete the
high HZCO concentrations, since lower values were obtained during
the rainy season. The calculated overall photolytic life time
ranged from 3.2 to
10.5
h, enough time to account for the
observed harmful effects of H2C0 upon the inhabitantes of Mexico
City
.
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