Author(s)

Abdullah S. Modaihsh, Fahd N. Al-Barakah, Mahmoud E. A. Nadeem, Mohamed O. Mahjoub^*

Department of Soil Science, College of Food and Agricultural Sciences, King Saud University, Riyadh, Kingdom of Saudi Arabia.

Mass concentrations of PM₁₀ and PM_2.5 for January 2012 up to October 2013 were measured at two sites; a suburban area, Riyadh airport (AP) and an urban area, King Fahd road district (KF) (densely trafficked site). Daily concentrations of both PM₁₀ and PM_2.5 measured at these two sites were highly variable. The temporal variation observed either for PM₁₀ or PM_2.5 was associated mainly with the dust events. The annual pattern of PM₁₀ and PM_2.5 at the AP station shows a significant increase in spring and summer (dusty seasons) where monthly mean concentrations of up to 696 μg·m^-3 PM₁₀ were recorded in March. PM₁₀ concentrations during winter months are significantly lower, with 65 μg·m^-3 measured in November and 78 μg·m^-3 measured in December. January exhibits PM₁₀ concentrations little above 100 μg·m^-3. Both PM₁₀ and PM_2.5 showed substantial variations at these two monitoring stations during the study period. In the ur-ban station (King Fahd), average annual PM₁₀ varied by up to roughly a factor of two. This variation implies that local emission sources in this site often contribute much (i.e. greater than half) of the PM₁₀ mass on annual average. The variation of monthly (temporal) mean PM₁₀ at KF station showed more or less similar results to the AP station. Higher concentrations were observed during spring and summer (12%, 17% and 13% in Feb., March and April respectively and 17, 15% during June and July). Starting from September and October, PM₁₀ concentrations started to drop to 7% and 8% respectively. The relationships between the mean values of suspended particle concentrations and meteorological variables (relative humidity ambient temperature and wind speed) were analyzed. The results demonstrate that the influence of weather factors upon dust particulates is largely inconclusive. However, At KF station a moderate positive correlation was observed between wind speed and PM.

PM₁₀, PM_2.5, Meteorological Data, Saudi Arabia, Riyadh

Modaihsh, A. , Al-Barakah, F. , Nadeem, M. and Mahjoub, M. (2015) Spatial and Temporal Variations of the Particulate Matter in Riyadh City, Saudi Arabia. Journal of Environmental Protection, 6, 1293-1307. doi: 10.4236/jep.2015.611113.