nvironmental Monitoring of NOX, Total Oxidants and the Implications for Photochemistry of Air Pollution over Ilorin Shed, Nigeria

Abstract

The assessment of oxides of nitrogen (NO X ) and total oxidants as ozone (O 3 ) over the air shed of a typical average tropical equatorial city monitored with the aid of high volume sampler for three years is presented using three urban site classes and a control. The mean concentrations for all sites during wet season (May October) were 3.31 ± 0.40 ppb for NO X , 21.86 ± 2.47 for O 3 while the dry season (November - April) mean concentration values were 2.03 ± 0.23 ppb for NO x and 32.44 ± 5.13 for O 3 . Mean value at the control site was an order of magnitude lower than the urban sites during the two seasons except concentration of O 3 higher during the dry season. Traffic density and trace gas concentrations showed good correlation of 0.98 (P<0.05). NO x was confirmed to be a strong precursor for O 3 formation. The influence of Harmattan dust in impeding the photochemistry of O 3 formation from November to January (NDJ) months was observed. The overall concentration levels of NOx and O 3 for the air shed are 2.67 ± 0.32 and 27.15 ± 3.8 respectively, within the limit of United States Environmental Protection Agency (USEPA) guidelines for air quality standards.