Farah Halek

Biodiesel is a renewable energy resource consisting of the alkyl monoesters of fatty acids obtained from vegetable oils, waste cooking oils, or animal fats. Biodiesel has been noticed recently as an alternative to fossil fuels. Previous studies have shown that biodiesel produces less pollutants compared to diesel fuel. Biodiesel fuel increases the emission of NO_x exceptionally. Recently, it has been found that antioxidant addition to biodiesel is a solution to solve the problem. The purpose of this research is to study the effect of antioxidants addition on the emissions of CO, HC, and NO_x from biodiesel fuel. Exhaust emissions of an agriculture diesel engine were studied using biodiesel blend with a 500 ppm propyl gallate (PrG) (propyl-3,4,5-trihydroxybenzoate) and butylated hydroxy anisole (BhA) (2-tert-butyl-4-methoxyphenol) as two major antioxidants. Biodiesel used in this research was prepared through NaOH catalyzed transesterification of a waste cooking oil that originally was taken from sunflower oil, with the assistance of ultrasonic homogenizer. After biodiesel production, five blends including neat diesel, B10, B20, B20 + 500 ppm PrG, and B20+ 500 ppm BhA were used as fuel and the emitted gases were analyzed. The results of this work demonstrated that the addition of antioxidants has no significant effect on lowering CO emission, as well as lowering HC; but the addition of antioxidants results in more efficient reduction of NO_x emission from diesel exhaust. In general, BhA showed better results compared to PrG.

Particulate matter is one of the most significant pollutants in indoor environments. The study of vertical profile concentration coefficients of different particulates leads us to figure out the most accurate pattern of vertical profile change of these hazardous particles. In this case, three different sizes of particulate vertical profile patterns, PM1.0, PM2.5, and PM10, were evaluated in indoors in the city of Karaj. Samplings of first and fourth floors of 5 buildings located in different areas of Karaj were conducted constantly during 2011. The results of Mahestan Station illustrate the highest average concentration of PM10 (173 µg/m3) whereas the RajaieShahr Station measurements indicates the highest average concentrations of PM2.5(66 µg/m3) and also PM1.0(51 µg/m3). Generally, the concentrations of the particulates in the first floors were higher than that in the fourth floors, and according to the air evaluation stations, all the particulates including PM1.0, PM2.5, and PM10 had concentrations higher than the annual standard.

The objective of this work was to evaluate the indoor-outdoor particle size distribution in elementary schools located in central parts of Tehran and to evaluate those parameters that could be influencing the indoor particles concentrations in the classrooms. Concentrations of particles including PM₁₀, PM_2.5 and PM_1.0, as some of the main air pollutants in Tehran, were measured in the schools, during winter 2009. It was found that the average indoor concentrations of PM₁₀, PM_2.5 and PM_1.0 were 274 µg/m³, 42 µg/m³ and 19 µg/m³, respectively, while the outdoor concentrations for these particles were 140 µg/m³, 38 µg/m³ and 22 µg/m³, respectively. The main factors influencing indoor particle pollution were found to be the outdoor concentrations of the particles and the physical activity of the students, but other factors such as the differences between indoor and outdoor temperatures, class size dimensions and types of boards in the classrooms had negligible effects.

In this paper, the photocatalytic decoloration of Acid Red 27 (AR27) has been investigated using ultraviolet (UV) irradiation in presence of SnO2 nanoparticles. SnO2 nanoparticles were synthesized via hydrothermal process. The SnO2 nanoparticles' average crystallite sizes derived from X-ray analyses which were synthesized for 2, 12 and 24 hrs were about 3.73, 5.31 and 7.6 nm, respectively. Brunauer-Emmett-Teller (BET) analyses showed high surface area of about 183, 120 and 90(m2/g), respectively for aforementioned synthesized samples. Our investigations indicated that reaction rate constant and photocatalytic efficiency of AR27 decoloration have a direct relation with SnO2 nanoparticles' specific surface areas and band gap energies. Decoloration kinetics was investigated by using Langmuir-Hinshelwood model. The values of the adsorption equilibrium constant, K[AR27], and the kinetic rate constant of surface reaction, kc, were found to be 0.0924 (l/mg) and 0.2535 (mg/l min), respectively.

In this work, the airborne particulate matter with an aerodynamic diameter less than 10 µm (PM₁₀) was fractionated in a six-stage high-volume cascade impactor to identify particulate size distribution in Tehran atmosphere. The study was conducted at 15 sites located in the north, south, east, west, and central parts of Tehran in 2005. Air samples were analyzed for 16 polycyclic aromatic hydrocarbons (PAHs) by HPLC. The daily PM₁₀ concentrations at the peak of traffic in roadside areas were found to be 106–560 µg m⁻³. The cumulated concentration sum of PAHs, based on 16 species, was found to have an average concentration of 380 ng m⁻³. Furthermore, it was found that more than 60% of PAHs belonged to the small particulate size range, having sizes of less than 0.49 µm, some containing benzo(ghi)perylene and indeno(123cd)pyrene (high molecular weight) with average concentrations of 8 and 6 ng m⁻³ and fluorene, phenanthrene, and fluoranthene (low molecular weight) with average concentrations of 14, 13, and 19 ng m⁻³, respectively. In addition, the results revealed that the lighter three- and four-ring PAH compounds were the most abundant pollutants in the air collected at all the sampling sites.

Outdoor concentrations of some elements such as iron, aluminum, magnesium, titanium, copper, zinc, lead, manganese, sulfur, chromium and arsenic in PM₁₀ and PM_2.5, was evaluated at four points in north-western part of Tehran in winter 2007. The total concentration of the elements in PM₁₀ and PM_2.5 at the north Karegar avenue found to be as high as 82.05 and 60.64 μg/m³, respectively, while at the Arjantin square it was measured to be 34.30 and 28.03 μg/m³. The emission sources of the trace elements were attributed to the adjoining local industries in the west parts of Tehran.