Air quality assessment of the emission from power plant and traffic at Al-Taneem area located at the northern part of the Holy City of Makkah, Saudi Arabia, is investigated. Concentration levels of different pollutants including nitrogen dioxide (NO(2)), sulfur dioxide (SO(2)), carbon monoxide (CO), ozone (O(3)), methane (CH(4)) and total hydrocarbons (THC) as well as some meteorological parameters (temperature, wind speed and wind direction) during the period from November 2002 to October 2003 were measured and analyzed. The results indicated that nitrogen oxides and carbon monoxide concentrations increase at the starting hours of the day. Sulphur dioxide concentrations were relatively low and constant. Ozone concentration trend showed the changes of the rate of the photochemical reactions. The distribution of the measured concentrations may be used for the development of numerical models and the estimation of air quality parameters in urban environment.

Study of the impact of traffic emissions on air quality around the Haram Mosque in Makkah, Saudi Arabia, was conducted experimentally, numerically and statistically. Experimental study was performed to measure existing air quality. Numerical study was done to model the extent of air movement and pollutant dispersion within and around the Haram area. Statistical study was conducted to determine correlation coefficients, auto-correlation and time lags of each pollutant. Pollutant measurements were carried out using an air quality mobile laboratory at three sites. Numerical calculations were made using an ISC-AERMOD dispersion model. Concentrations of traffic emissions including nitrogen dioxide (NO₂), sulfur dioxide (SO₂), carbon monoxide (CO), ozone (O₃) and airborne particulate material under 10 μm diameter (PM₁₀) are presented and analyzed. The calculated concentrations are validated by comparing with observed values at the three sites. The results indicate good agreement between calculated concentrations and observed values, which demonstrate satisfactory model performance. Results show that the Haram area is experiencing high concentrations of dust. High buildings around the Haram Mosque act as flow obstacles. Mean pollutant dispersion was toward the south and southeast during January and June. Highest mean concentrations were observed in January and June.

In contrary to O3, NO has higher concentrations in autumn and winter than those in summer and spring seasons. The highest concentrations of NO2, NOx, SO2, CO, and TNMHCs were found in autumn and spring, whereas the lowest concentrations were found in summer and winter. THC and CH4 have no significant change over winter, autumn and summer seasons, while their concentrations decrease sharply in spring. Although the studied area does not suffer from NO2, O3, SO2 and CO pollution and no health risk, comprehensive and long-term air quality management programmes are needed in order to keep air quality in a good condition.

In this paper, the impact of natural and anthropogenic sources on particulate matter with diameter less than 10 µm (PM 10) was investigated in Jeddah urban area, Saudi Arabia to identify and quantify the major particle pollution source classes. Hourly data of PM 10 and other gaseous pollutants (NO x , CO, SO 2 and O 3) and meteorological factors (temperature, relative humidity, atmospheric pressure, wind speed and wind direction) were collected at two air quality monitoring sites for the period of March 2008 to February 2009. The air mass origin was determined using 5-day backward trajectories arriving to Jeddah by using HYSPLIT model. Results show that the PM 10 Daily Limit Value was exceeded. The most frequent air masses entering Jeddah and thereby influencing PM 10 concentrations come from the East, specifically the SE and NE directions, 84% of the trajectories were originated over the Arabian Peninsula including Saudi Arabia mainland and the Arabian Gulf. The Mediterranean Sea and southern Europe were the origin source of 8% of the air mass trajectories, another 8% were originated from North Africa and Sahara Desert. The majority of PM 10 episodes were attributed to the intrusion of dust to Jeddah urban air.

Data describing PM10 concentrations and some meteorological parameters (temperature, relative humidity and wind speeds) during January 2011-December 2011 were analyzed and evaluated. They were collected from an ambient air quality station in the industrial area in south Jeddah. The monthly and seasonal variations of PM10 concentrations and factors affecting them were evaluated. It was found that the daily average concentrations of PM10 ranged from 45 to 506 µg/m 3 with a mean value of 119 µg/m 3 during the period of study. Almost all the mean 24-h concentrations of PM10 exceeded the WHO air quality standards for maximum 24-h concentration (50 μg/m 3). The highest concentrations of PM10 were found in spring, whereas the lowest levels were detected in autumn season. The mean daily concentrations of PM10 were 120, 144, 116 and 89 µg/m 3 in winter, spring, summer and autumn, respectively. PM10 concentrations were relatively higher in weekdays than weekends during the different seasons. The weekdays/weekends concentration ratios were 1.18 (winter), 1.36 (spring), 1.41 (summer), 1.29 (autumn) and 1.32 (annual). PM10 concentrations were higher in dust storm compared to non-dust storm days. The dust storm /non-dust storm concentration ratios was 3.14.