Mohammad W. Kadi

Air pollution causes environmental and health problems around the world. In this study, ambient particulate matter with an aerodynamic diameter equal to or less than 10 microns (PM₁₀) has been collected at three different locations in Jeddah city, Saudi Arabia. The locations are characterized by differences in terms of traffic, residential intensity, industrial, and non-road mobile machinery activities. The monthly and annual mass concentration of the PM₁₀ exceeds the recommended annual limit of the World Health Organization (15 µg/m³) and the European air quality standard (40 µg/m³) at the three locations. The collected PM₁₀ samples as well as a certified reference material of atmospheric particulates (NIST 1678a) were digested in aqua regia using microwave digestion. The quantitative elemental analysis was carried out using inductively coupled plasma mass spectrometry. The variations of the elemental concentration in terms of workdays, weekends, seasons, and annual were determined at the three locations. The spatial and temporal elemental variations were found to be different between the three sites, pointing to local influences that should be further evaluated. The concentration of Cd was found to be high and may cause health problems.

People may spend a significant amount of their daily time in cars and thus be exposed to chemicals present in car dust. Various chemicals are emitted from during car use, contaminating the car dust. In this study, we compiled published and unpublished data on the occurrence of phthalates, flame retardants (FRs), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) in Saudi car dust. Phthalates, a class of chemical commonly used as plasticizers in different car parts, were the major pollutants found in car dust, with a median value of ∑phthalates 1,279,000 ng/g. Among other chemicals, organophosphate flame retardants (OPFRs) were found to be between 1500–90,500 ng/g, which indicates their use as alternative FRs in the car industry. The daily exposure to Saudi drivers (regular and taxi drivers) was below the respective reference dose (RfD) values of the individual chemicals. However, the estimated incremental lifetime cancer risk (ILCR) values due to chronic exposure to these chemicals was >1 × 10⁻⁵ for taxi drivers for phthalates and PAHs, indicating that the long-term exposure to these chemicals is a cause of concern for drivers who spend considerable time in cars. The study has some limitations, due to the small number of samples, lack of updated RfD values, and missing cancer slope factors for many studied chemicals. Despite these limitations, this study indicates the possible range of exposure to drivers from chemicals in car dust and warrants further extensive studies to confirm these patterns.

Platinum group elements (PGE) including Ru, Rh, Pt and Pd have been quantified in air particulate matter with an aerodynamic diameter equal or less than 10 microns (PM₁₀) using inductively coupled plasma mass spectrometry (ICP-MS). PM₁₀ aerosols have been collected from three sites representing various activities in Jeddah city, Saudi Arabia. These locations are residential site with heavy traffic, industrial site and heavy traffic and a light traffic site outside the city. To obtain reasonable data of the PGE concentrations, a group from 10 to 15 PM₁₀ samples were collected every month. The annual and seasonal variation of the mass concentration of the PGE were demonstrated. In all locations, Pt and Pd were relatively higher than Ru and Rh possibly because their main use is in automobile catalytic converters. Concentrations of observed PGE in PM₁₀ could be arranged in ascending order as: Rh < Ru < Pd < Pt. In case of Ru and Pt, there are clear similarities in terms of the overall mean concentrations at the sampling locations. Due to the high concentration of Ru, Rh and Pd at low traffic site, there are certainly other sources of these elements rather than vehicle catalytic converters. However, at the industrial/heavy traffic location, high concentrations of Ru were detected during February 2015. In addition, high Pt concentrations were also detected at the light traffic site during May 2015. Results indicate that Pt source in PM₁₀ is mainly the automobile catalytic converters.

Elements associated with total suspended particulate matter (TSP) in Jeddah city were determined. Using high-volume samplers, TSP samples were simultaneously collected over a one-year period from seven sampling sites. Samples were analyzed for Al, Ba, Ca, Cu, Mg, Fe, Mn, Zn, Ti, V, Cr, Co, Ni, As, and Sr. Results revealed great dependence of element contents on spatial and temporal variations. Two sites characterized by busy roads, workshops, heavy population, and heavy trucking have high levels of all measured elements. Concentrations of most elements at the two sites exhibit strong spatial gradients and concentrations of elements at these sites are higher than other locations. The highest concentrations of elements were observed during June–August because of dust storms, significant increase in energy consumption, and active surface winds. Enrichment factors of elements at the high-level sites have values in the range >10~60 while for Cu and Zn the enrichment factors are much higher (~0–>700) indicating that greater percentage of TSP composition for these three elements in air comes from anthropogenic activities.

ZrO₂-SiO₂mixed oxides were prepared via the sol-gel method. Photo-assisted deposition was utilized for doping the prepared mixed oxide with 0.1, 0.2, 0.3, and 0.4 wt% of Pt. XRD spectra showed that doping did not result in the incorporation of Pt within the crystal structure of the material. UV-reflectance spectrometry showed that the band gap of ZrO₂-SiO₂decreased from 3.04 eV to 2.48 eV with 0.4 wt% Pt doping. The results show a specific surface area increase of 20%. Enhanced photocatalysis of Pt/ZrO₂-SiO₂was successfully tested on photo degradation of cyanide under illumination of visible light. 100% conversion was achieved within 20 min with 0.3 wt% of Pt doped ZrO₂-SiO₂.