Ozone (O3) ambient levels as a secondary airborne precursor in Fahaheel urban area, the State of Kuwait

Two years of continuous monitoring data over two time-spans (2004-2005 and 2014-2015) were used to investigate the relationship between ozone (O-3) and nitrogen oxides (NOX approximate to NO + NO2) in Fahaheel urban area (Kuwait). Their relationship was used to understand their chemical reactions and the NO2 and O-3 concentration ratio to gain an insight into the sources of total atmospheric oxides (O-X = O-3 + NO2) levels. A Chemical Mass Balance (CMB) model was developed to detect likely point sources around the monitoring station and quantify their contribution to the overall air pollution load. Hourly diurnal variations in O-3 ground level concentrations during weekends showed a slight increase in O-3 levels. In addition, it was observed that overall hourly average O-3 concentration reached higher levels during weekdays and weekends in 2004-2005 compared to 2014-2015. The concentration of photochemical oxidants (e.g., O-3 and NO2) can be decreased by controlling the emissions of their precursors; NOX and VOCs. The net effect of NOX emissions on O-3 concentrations was negative with a weak exponential decline correlation between NOX and O-3, indicating Fahaheel urban area's VOC-sensitive characteristics. For all years considered, the slopes of the linear O-X-NOX relationships were higher during daytime compared to night-time, showing that NO2 oxidations were dominant during daytime and that O-3 net production was high. The study also showed the high NOX oxidation level and the possible presence of O-3 net production. The slopes during night-time indicated that NO2 consumption exceeded its formation rate. During day and night-time, the NO2/NOX ratio was found to decline significantly as newly emitted NOX increased, supporting the area's VOC-sensitive nature. By setting up a CMB model around the Fahaheel receptor point, it was revealed that downstream petroleum facilities have been the major contributor to pollutants environmental load over the years.