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Al Bayḑā’, Libya

Ali Rahoma U.,Omer El Mukhtar University
American Journal of Environmental Sciences | Year: 2010

Problem statement: Particle counting and sizing of atmospheric aerosols by electro-optical methods are complex and absolute interpretation of measurements is difficult, so, the scattered light varies in a complicated manner with the system of optics as well as with the size and physical characteristics of particles. Approach: The estimation of the air aerosol number concentration variation was carried out in this study making use of data obtained from the Helwan, Egypt. The aerosol number concentration was determined indirectly, making use of the intensity of light scattered by particles. The scattered light intensity was proportional to the average number concentration of the aerosols. Results: The results were presented from desert zone from using Eppley direct solar irradiance measurements as a base on 10 years of data collection (1991-2000). Conclusion: The differences among the region were characterized mainly by their different climate change taken in consideration in the spectral region 250-900 nm. Most of the particles are greater than 10 μm in aerodynamic diameter and 60-80% of particles was 5-10 μm and was trapped in the nasopharyngeal region. This showed an idealized size distribution of particulate matter in ambient air and measurement techniques to cover specific fractions. The columnar volume radius distributions of aerosol 3-6 μm showed the aerosol optical depth is less than 0.31 for λ = 500-630 nm. The behavior in a more turbidity, when the aerosol optical depth is about 0.25 for 630-695 nm, gives approximately fixed volume radius distributions of aerosols between 5-10 μm. The small size fraction of aerosols, measured as PM10 and PM2.5, rather than the larger particles, was considered to be responsible for most of the health effects. Source

Ali Rahoma U.,Omer El Mukhtar University | Emara E.,University of Sfax
American Journal of Infectious Diseases | Year: 2010

Problem statement: The small size fraction of aerosols, measured as PM10 and PM2.5, rather than the larger particles, is considered to be responsible for most of the health effects. Such particles have a relatively long residence time in the atmosphere and can therefore travel over long distances. Hence, a large portion of ambient concentrations of PM10 and in particular of particles with an aerodynamic diameter less than 2.5 μm (PM2.5), can be attributed to long range trans boundary air pollution or to other remote sources. The estimates of exposure and of health effects are based on a number of uncertain assumptions and data sets, as described in previous article. Approach: In industrialized Middle East countries, the daily deposition of PM10 particles in the lungs is roughly 250 μg day-1, which represents a small dose in terms of traditional toxicology studies. Studies of PM10 have considered this total material but have not asked how much its chemical or physical characteristics contribute to its total toxicity. Results: This article focuses on the description of the present knowledge on PM10 concentration fields and predominant sources contributing to PM10 from long range transport of pollution. PM10 is a complex mixture of many known and unknown components; therefore, a short introduction on the composition of PM10 is given. The studies denote to the African dust from mean PM10 levels background levels are still 5-10 mg m3 higher in the Eastern Basin (EMB) when compared with those in the Western (WMB), mainly due to the higher anthropogenic and sea spray loads. Conclusion: As regards for the seasonal trends, these are largely driven by the occurrence of African dust events, resulting in a spring-early summer maximum over the EMB and a clear summer maximum in the WMB, although in this later region the recirculation of aged air masses play an important role. Furthermore, a marked seasonal trend is still evident when subtracting the African dust load. This is characterized by a high summer maximum (driven by low precipitation, high isolation) and a winter minimum (intense synoptic winds). © 2010 Science Publications. Source

Hassan A.H.,Omer El Mukhtar University | Ali Rahoma U.,Omer El Mukhtar University
American Journal of Environmental Sciences | Year: 2010

Problem statement: Measurement of the different components of solar radiation and fractions of these components for the global (horizontal and tracker), direct (white and three colors, yellow, red and infrared) and diffuse solar radiation during the solar eclipse, 29 March 2006 at Tobruq, Libya (Lat. 32.08°N and Long. 23.98°E). The time interval of solar eclipse was 2 h: 40 m and the maximum magnitude of eclipse at this region was 0.995. Conclusion: The results showed that the maximum percent of color in the total direct solar radiation during the true eclipse from the first contact to the end contact was in the infrared, where the percent were in the green (11.74%), yellow (15.69%), red (14.88%) and infrared (57.68%). © 2010 Science Publications. Source

Khalaf H.A.,Omer El Mukhtar University | Mansour S.E.,Omer El Mukhtar University | El-Madani E.A.,Omer El Mukhtar University
Monatshefte fur Chemie | Year: 2010

Stannia, sulfated stannia, and Cu-modified sulfated stannia samples were prepared by an impregnation method using different loading levels of Cu (5, 10, and 20% by weight). These samples were characterized by means of thermal gravimetric analysis (TGA and DTA), X-ray powder diffraction (XRD), and nitrogen sorption at 77 K. Potentiometric titration was used to characterize the surface acidity of these samples and their catalytic activity was investigated by phenol hydroxylation in the presence of hydrogen peroxide at 333 K. The obtained data revealed sulfated species with different thermal stabilities in the samples containing Cu, and the rutile structure of stannia remained unchanged by the addition of sulfate and Cu. A surface texture study showed that Cu modification and the addition of sulfate resulted in modified surface area and porosity. The addition of copper to sulfated stannia increases the acid strength. Thus, Cu-modified sulfated stannia samples have higher catalytic activity towards phenol hydroxylation and selectivity towards hydroquinone production. © Springer-Verlag 2010. Source

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