Particulate matter originates from a variety of sources in Makkah, Saudi Arabia. Since Makkah is situated in an arid region and is a very busy city due to its religious importance in the Muslim world, PM 10 concentrations here exceed the international and national air quality standards set for the protection of human health. The main aim of this paper is to model PM 10 concentrations with the aid of meteorological variables (wind speed, wind direction, temperature, and relative humidity) and traffic related air pollutant concentrations (carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO 2 ), sulphur dioxide (SO 2 ) and lag_PM 10 concentrations), which are measured at the same location near Al-Haram (the Holy Mosque) in Makkah. A Generalized Additive Model was developed for predicting hourly PM 10 concentrations. Predicted and observed PM 10 concentrations are compared, and several metrics, including the coefficients of determination (R 2 = 0.52), Root Mean Square Error (RMSE = 84), Fractional Bias (FB = -0.22) and Factor of 2 (FAC2 = 0.88), are calculated to assess the performance of the model. The results of these, along with a graphical comparison of the predicted and observed concentrations, show that model is able to perform well. While effects of all the covariates were significant (p-value < 0.01), the meteorological variables, such as temperature and wind speed, seem to be the major controlling factors with regard to PM 10 concentrations. Traffic related air pollutants showed a weak association with PM 10 concentrations, suggesting road traffic is not the major source of these. No modeling study has been published with regards to air pollution in Makkah and thus this is the first work of this kind. Further work is required to characterize road traffic flow, speed and composition and quantify the contribution of each source, which is part of the ongoing project for managing the air quality in Makkah.

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This work has been devoted to study TSP, PM 10 and PM 2.5 in the atmosphere of Makkah and the Mina valley during the Ramadan and Hajj periods, 1424 and 1425 H. On the occasion of Hajj, about 2.5 million persons gather in Makkah and move to Mina valley (4 km 2 ), 7 km outside east of Makkah. Pilgrims spend 3 nights in the valley. Congested traffic and the high rates of emissions in such a valley of small area coupled with severe weather conditions, make the area ideal for the accumulation of air pollutants. The present investigation shows that the diurnal cycle of PM 10 in air coincides with the pattern of traffic movements. Particulate matters (PM 10 ) daily concentrations in the atmosphere of the Mina valley ranged between 191-262µg/m 3 during the presence of the pilgrims in Mina compared to the European standard of 50µg/m 3 . These concentrations represent 34%-40% of TSP. These high PM 10 concentrations are due to the massive transportation movements at Mina valley. Moreover, TSP concentrations reached 665µg/m 3 in the Makkah atmosphere during the last ten days of Ramadan compared to the Saudi standard of 340µg/m 3 . Chemical analysis of PM 10 indicated high levels of sulphates, ammonium, nitrates and chlorides. For example, the concentrations of nitrates and sulphates of PM 10 were about 4.9% and 6.1% respectively, compared to 2.1% of nitrates and 2.7% of sulphates in TSP. Health dangers that might be encountered by pilgrims due to these pollutants were estimated. It is recommended to set a well planned air quality management program to protect the air of Makkah.

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[1] Solar UV radiation plays a very significant role in terms of atmospheric chemistry. The UV radiation that reaches the troposphere drives the photodissociation of tropospheric species whose photolysis energies fall in the range of these wavelengths. The relevant measure of radiation for atmospheric chemistry is actinic flux, but the great majority of UV measurements, not common in themselves, are UV irradiance (radiation on a flat surface). Spectral UV irradiance was measured in Manchester, UK (78 m altitude, 53.28°N, 2.14°W) using a moderate bandwidth filter radiometer (GUV-541) that has five channels in the UV region with center wavelengths at 305, 313, 320, 340, and 380 nm and band-pass functions of approximately 10 nm. This study describes a new method of deriving the photolysis rate of O 3 , NO 2 , and CH 2 O utilizing the GUV irradiance measurements. The measured irradiance was compared with independently measured photolysis rates determined from the actinic flux measured by a Bentham spectroradiometer on a clear sky day. On the reference day, a linear regression of GUV global irradiance to simultaneous photolysis rate measurements was performed to generate scale factors for each optical channel. The results compare favorably with the general uncertainty in photolysis measurements of about 20%. A further separate comparison is made with comparable filter radiometers.

Ground level ozone concentration is dependent on its precursors, such as Nitrogen Oxides (NO x ) and hydrocarbons (HCs) and meteorological parameters, most importantly air temperature. Positive ozone-temperature slope at average temperature is well-documented. However, how this relationship breaks at extremely high temperature in hotter climates is still debatable. As this could have implications for long term global modelling predictions, this paper explores evidence for a negative ozone-temperature slope during atypically high temperature events in Makkah, Saudi Arabia, where temperature levels as high as 50°C are recorded. At temperature levels (15-42°C) statistical analysis showed positive ozone-temperature slopes, however the slopes became negative at atypically high temperature levels (> 42°C). Using data when hourly mean temperature was greater than 42°C, Quantile Regression Model (QRM) showed negative ozone-temperature slopes. The negative slopes at quantile 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 and 0.9 were -1.88, -5.83, -7.89, -7.08, -11.11, -15.00, -18.28, and -28.57 µg/m 3 /°C, respectively. Mean slope determined by linear regression was -11.51 µg/m 3 /°C. Furthermore, the negative slopes were stronger at higher quantiles of ozone distribution, indicating non-linearities in the association of ozone and temperature. Reduction in the levels of ozone precursors, such as total hydrocarbons (THCs) and nitrogen dioxide (NO 2 ) is probably the most likely reason for the negative ozone-temperature slope at extremely high temperature. Previously concerns have been expressed that under the warming climate scenario increasing temperature may further increase ozone levels, particularly in urban areas during pollution episodes, however this study suggests the opposite at extremely high temperature in hot arid climatic conditions.

This study has measured the incident solar UV radiation and the concentrations of three pollutants of O 3 , NO 2 and NO in atmosphere of Makkah, Saudi Arabia (322m altitude, 21 o .24 N, 39 o .51E) during to different seasons of winter and spring in 2007. A moderate bandwidth filter radiometer (GUV-2511) that has six channels in the UV region with centre wavelengths at 305, 313, 320, 340, 380 and 395nm and bandpass functions of approximately 10 nm was used to measure the incident UV radiation. The concentrations of O 3 and NOx were measured by two ambient Monitors of APOA-360 and APNA-360 respectively. The two periods of measurements were from 8 th to 17 th of Zul-Hijah 1427L (from 28/12/2006 to 6/1/2007) for winter time and between 21/4 and 1/5/1428L (8 -17/5/2007) for spring season. It was found that the highest concentrations of approximately 135, 200 and 365 mg/m 3 were recorded for O 3 , NO 2 and NO pollutants respectively with maximum incident UV radiation at midday of 210 mW/cm 2 during winter time (Zul-Hijah 1428L). However, in spring season, the maximum recorded values for O 3 , NO 2 and NO species were approximately 147, 100 and 95 mg/m 3 respectively with largest incident UV radiation at midday of 300 mW/cm 2 . The ozone concentration may significantly increases if two factors (high vehicles emission and large incident solar UV radiation) combined together, which could occur when the hajj month synchronizes with spring or summer seasons in the coming few years. As a result, a big challenge of air quality in Makkah and hence pilgrims health problems will be encountered, otherwise new means of transportation and air quality controlled are required.

The present investigation aims to study temporal and spatial variation in the concentrations of PM 10 , CO and noise levels at the central area (322 m altitude, 21 o .25 N, 39 o .52 E) in Makkah, Saudi Arabia, during hajj season in 1429H (2008). Measurements of PM 10 , CO and noise levels were conducted using the High Volume Sampler of PM 10 , CO gas monitor and the Sound level Meter of model CR812B, respectively. The daily averaged measured PM 10 concentrations at the central area were high and ranged between 85 and 200 µg/m 3 . Despite such PM 10 concentrations are lower than the recorded one (250 µg/m 3 ) by previous studies and are within the permissible limits by GERRI (340 µg/m 3 ) but they were still exceeding the recommended limits of PM 10 (20 µg/m 3 ) by WHO. However, the averaged measured concentrations of CO were less than 20 mg/m 3 /hr except Tunnel (1) that reached 97 mg/m 3 /hr. The measured LAeq at the central area sites varied between 71 and 98 dB exceeding the recommended value of 70 dB by WHO. This study also discussed the temporal variation of all these pollutants during hajj season and its expected sources in the central area and its health effects on pilgrims. The solutions were suggested to improve the air quality. Most important suggestion is adopting a new public transportation system at this central area in Makkah such as monorail, trams or train networks that would extremely reduce air pollutant concentrations and noise levels. A comprehensive program is required for the safety environmental management.