Ground based MAX-DOAS observations of tropospheric trace gases in San Salvador, El Salvador

Full text: High levels of air pollution in different Central Americas capital cities were reported a few years ago, being San Salvador metropolitan area the place with the highest concentration values of several pollutants. The high levels of these pollutants, in some measuring points, exceed the limit values established by the environmental law of the republic of El Salvador and also those established by EPA and WHO. In this work we report on levels of HCHO, O4 and NO2 obtained by using ground based Multi-Axis Differential Absorption Spectroscopy (MAX-DOAS) during a campaign performed in San Salvador on February 2011. The experimental set-up used in the DOAS-measurements consists of a home-made-telescope coupled to an spectrometer by using an optical ber. The spectral resolution is around 1.2 nm. The diurnal behavior of NO2-dSCD during the working days is characterized by an strong increase in the morning. It could be associated to emissions from vehicles during the rush hours. The obtained dSCD values for HCHO are similar to the obtained by other authors in cities with higher population. The oxygen dimer O4 levels were also measured in order to estimate the aerosol extinction. Similar trends are observed for HCHO and O4. These results could be explained by a change in the aerosol extinction and meteorological conditions. (author)