Khoder M I
Department of Air Pollution Research, National Research Centre, Dokki, Giza, Egypt.
Environ Monit Assess. 2009 Feb;149(1-4):349-62. doi: 10.1007/s10661-008-0208-7. Epub 2008 Feb 15.
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.
2004年12月至2005年11月期间，在大开罗的一个市区（吉萨省哈勒姆）监测了地面臭氧（O₃）浓度。在冬季和夏季，还测量了二氧化氮（NO₂）和一氧化氮（NO）浓度以及气象参数。在冬季、春季、夏季和秋季，白天O₃的平均值分别为43.89、65.30、91.30和58.10 ppb，全天（每日）的平均值分别为29.69、47.80、64.00和42.70 ppb。四个季节中O₃浓度的日变化周期显示在中午时分出现单峰，由于当地的光化学产生，夏季的O₃水平最高。冬季和夏季NO和NO₂浓度的日变化显示出与交通密度相关的两个每日峰值。冬季发现的NOx水平最高。春季、夏季、秋季和全年白天O₃平均浓度分别有近75%、100%、34.78%和52.63%超过了埃及和欧盟白天（8小时）O₃浓度的空气质量标准（60 ppb）。夏季和全年白天小时浓度分别约有41.14%和10.39%以及每日小时浓度分别有14.93%和3.77%超过了埃及最大每小时O₃浓度标准（100 ppb），并且在研究区域（哈勒姆）以相同百分比代表的时间段内形成了光化学烟雾。这是基于光化学烟雾通常在O₃浓度超过100 ppb时发生这一事实。周末O₃前体（NO和NO₂）的浓度低于工作日，而周末的O₃水平与工作日相比更高。这一发现现象被称为“周末效应”。在两个季节中O₃与温度之间以及夏季O₃与相对湿度之间发现了显著的正相关系数，表明高温和高相对湿度以及强烈的太阳辐射（夏季）是导致高O₃浓度形成的原因。
