Diurnal, seasonal and weekdays–weekends variations of ground level ozone concentrations in an urban area in greater Cairo

Abstract

Ground level ozone (O3) concentration was monitored during the period of December 2004 to November 2005 in an urban area in Greater Cairo (Haram, Giza). During the winter and summer seasons, nitrogen dioxide (NO2) and nitric oxide(NO) concentrations and meteorological parameters were also measured. The mean values of O3 were 43.89, 65.30, 91.30 and 58.10 ppb in daytime and 29.69, 47.80, 64.00 and 42.70 ppb in whole day (daily) during the winter, spring, summer and autumn seasons, respectively. The diurnal cycles of O3 concentrations during the four seasons revealed a uni-modal peak in the mid-day time, with highest O3 levels in summer due to the local photochemical production. The diurnal variations in NO and NO2 concentrations during the winter and summer showed two daily peaks linked to traffic density. The highest levels of NOx were found in winter. Nearly, 75%, 100%, 34.78% and 52.63% of the mean daytime concentrations of O3 during spring,summer, autumn and the whole year, respectively, exceeded the Egyptian and European Union air quality standards (60 ppb) for daytime (8-h) O3 concentration. About, 41.14% and 10.39% of the daytime hours concentrations and 14.93% and 3.77% of the daily hour concentrations in summer and the whole year, respectively, exceeded the Egyptian standard (100 ppb) for maximum hourly O3 concentration, and photochemical smog is formed in the study area (Haram) during a periods represented by the same percentages. This was based on the fact that photochemical smog usually occurs when O3 concentration exceeds 100 ppb. The concentrations of O3 precursors (NO and NO2) in weekends were lower than those found in weekdays, whereas the O3 levels during the weekends were high compared with weekdays. This finding phenomenon is known as the "weekend effect". Significant positive correlation coefficients were found between O3 and temperature in both seasons and between O3 and relative humidity in summer season, indicating that high temperature and high relative humidity besides the intense solar radiation (in summer) are responsible for the formation of high O3 concentrations.

Spatial Distribution and Temporal Variation in Ambient Ozone and Its Associated NOx in the Atmosphere of Jeddah City, Saudi Arabia

“…The seasonal variation in NO x with an increasing trend towards the winter has been reported by other authors in Cairo (Khodeir, 2009); Dallas (Smith et al, 2011); Delhi (Guttikunda and Gurjar, 2011) and New Jersey (RobertsSemple et al, 2012). Such variations could be attributed to the poor dependence of NO x on meteorological conditions.…”

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

“…For example, Shanghai, the largest city in China with a population of roughly 23 million, has undergone rapid development; between 1996 and 2008 industrial gross output increased by ≈ 4 times and the number of cars increased from 0.47 to 2.61 million (Tie et al, 2013). Other megacities in which vehicles are cited as the top or among the top sources of ozone precursors are Cairo, Delhi, Istanbul, Los Angeles, New York, Mexico City, Sao Paulo and the Ruhr-Rhein metropolitan region (Chelani, 2012;de Fatima et al, 2012;Parrish et al, 2011;Khoder, 2009;Im and Kanakidou, 2012;Melkonyan and Kuttler, 2012;Bon et al, 2011). In cities like Lagos in Nigeria it is a combination of traffic and open biomass burning driving large ozone exceedances from emission of NMVOCs (Marais et al, 2014).…”

Weekend-Weekday Effect Assessment for O3, NOx, CO and PM10 in Andalusia, Spain (2003-2008)

“…The weekly pattern of air pollutants is of general interest, and studies have been carried out in North America (Blanchard and Tanenbaum, 2003;Pun et al, 2003;Murphy et al, 2007;Koo et al, 2012), Europe (Brönnimann and Neu, 1997;Pont and Fontan, 2001;Jenkin et al, 2002 Paschalidou andKassomenos, 2004), Mexico (Stephens et al, 2008), Japan (Sadanaga et al, 2012), India (Debaje and Kakade, 2006;Pudasainee et al, 2010;Srimuruganandam and Nagendra, 2011) and Egypt (Khoder et al, 2009). Some of these studies analysed the influence of meteorological parameters, such as temperature and radiation, on the occurrence of the weekend effect (Brönnimann and Neu, 1997).…”