Abstract
Concentrations of ambient ozone (O3) and nitrogen oxides (NOx) were measured continuously for a period of 12 months in the city of Jeddah from December 2011 to December 2012. Meteorological parameters, wind speed, temperature, and relative humidity were also monitored. Concentrations of ground O3 were found to be highly dependent on the NOx diurnal cycle and wind speed. Nitrogen oxides were found to exceed air quality standards, especially in industrial sites, while O3 concentrations were found to exceed 40 ppb, averaged over 1 h, on more than 24% of the measured days in the rural sites. Furthermore, they exceeded 30% in all other areas (i.e., the urban ones). O3 and NOx were inversely related. The highest average NOx concentration (96 ppb) occurred in a rural area downwind of a desalination plant, while the average O3 concentration peaked in a rural area upwind of a desalination plant, reaching 63.5 ppb, although it also reached 72.6 in another rural area, and we consider this latter result as the background figure in the present study. The seasonal variations of O3 were more distinct than those of NOx. To the best of our knowledge, this is the first report providing comprehensive background information on air quality in an arid area of the developing world.
Highlights
Air Quality in Urban areas is affected mainly by photochemical oxidants (Han et al, 2011)
Meteorological Conditions The principal meteorological conditions recorded in the present study were wind speed, wind direction, temperature, relative humidity and atmospheric pressure in order to evaluate the influence they might have on ozone concentrations
The present study analyzed the concentrations of NO, NO2, nitrogen oxides (NOx) and O3 measured in Jeddah city over 365 complete days in 2012
Summary
Air Quality in Urban areas is affected mainly by photochemical oxidants (Han et al, 2011). Increased combustion of fossil fuels in the last century is responsible for the progressive change in the atmospheric composition Air pollutants, such as carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxides (NOx), volatile organic compounds (VOCs), ozone (O3), heavy metals, and respirable particulate matter (PM2.5 and PM10), differ in their chemical composition, reaction properties, emission, time of disintegration and ability to diffuse in long or short distances (Kampa and Castanas, 2008). The relation between ozone and its two main precursors, NOx (NO and NO2) and volatile organic compounds (VOC), represents one of the major scientific challenges associated with urban air pollution (Sillman, 1999). It is well known that the ozone concentrations in ambient air increase with increase in the intensity of radiation and temperature on the clear days (Nishanth et al, 2012). The magnitude of ozone concentration variations is high in clear days than
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