OXIDES OF NITROGEN AND TOTAL OXIDANTS DETERMINATION: THE IMPLICATIONS FOR PHOTOCHEMISTRY OF AIR POLLUTION OVER LAGOS NIGERIA

Abstract

The assessment of oxides of nitrogen (N0x) total oxidants as ozone(O3) over the air sheds of a typical city that is highly congested with a high intensity of marine, vehicular, and industrial activities monitored during both wet and dry seasons is presented using four urban location classes and a control. The mean ppb concentrations for all zones during wet season (May - October) were 3.00 ± 0.24 for NOx, 9.87 ± 0.99 for O3 while the dry season (November- April) mean ppb concentration values were 6.73 ± 0.51 for NOx and 36.22 ± 5.76 for O3 in Lagos. Mean value at the control location in order of magnitude was lower than the urban locations during the two seasons except for the concentration of O3. Traffic density and trace gas concentration showed good correlation of 0.98 (P<0.05). NOx was confirmed to be a strong precursor for O3 formation. The influence of Harmattan dust in impeding the photochemistry of O3 formation during the November, December and January (NDJ) months was observed. The overall concentration levels of NOx and O3 for the Lagos air sheds were 4.87 ± 0.38 and 23.05 ± 3.38. However, the values are within the limit of United States Environmental Protection Agency (USEPA) guidelines for air quality standards.

Author

Abdu Raheem A. M.O., Adekola F. A. - Department of Chemistry, University of Ilorin