The Impact of Traffic Emission on Air Quality in an 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.

Diurnal and Seasonal Variations of Surface Ozone and Its Precursors in the Atmosphere of Yanbu, Saudi Arabia

Surface ozone (O3) and its precursor’s gases (nitrogen monoxide (NO), nitrogen dioxide (NO2), nitrogen oxides (NOx), carbon monoxide (CO), methane (CH4) and non-methane hydrocarbons (NMHCs), and sulfur dioxide (SO2) were measured in Yanbu, Saudi Arabia from January 2004-December 2004. The annual average concentrations of O3, NO, NO2, NOx, SO2, CO, CH4, TNMHCs and THC were 22.51 ppb, 15.58 ppb, 17.25 ppb, 23.84 ppb, 6.66 ppb, 165.13 ppb, 3.44 ppm, 0.56 ppm and 3.88 ppm, respectively. The SO2/NOx and SO2/NO2 concentration ratios during the period of study indicate that the mobile emissions are the predominant sources in yanbu. The diurnal cycles of O3 concentrations revealed highest levels in the daytime and lowest levels in night time. The diurnal variations of NO, NO2, NOx, SO2, CO, NMHCs concentrations were similar and showed peaks concentrations linked to traffic density, boundary layer mixing processes and chemical processes in the atmosphere. The mean concentrations of O3 in different seasons follow the order of summer > spring > autumn > winter. 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.

Impact of Remote and Local Sources on Particulate Matter in Urban Environment

In this paper, the impact of natural and anthropogenic sources on particulate matter with diameter less than 10 μm (PM10) was investigated in Jeddah urban area, Saudi Arabia to identify and quantify the major particle pollution source classes. Hourly data of PM10 and other gaseous pollutants (NOx, CO, SO2 and O3) 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 PM10 Daily Limit Value was exceeded. The most frequent air masses entering Jeddah and thereby influencing PM10 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 PM10 episodes were attributed to the intrusion of dust to Jeddah urban air.