Faramarz Moattar

Purpose: This paper aims to present the most influential factors on classroom indoor PM_2.5 (Particulate Matter < 2.5 µ), determining the level of PM_2.5 concentration in five pre-schools located in the most densely populated district of the Tehran metropolitan area (district 6) as a case study to consider the children's exposure to air pollutants and introducing a suitable model, for the first time, to predict PM_2.5 concentration changes, inside pre-schools.Design/methodology/approach: Indoor and outdoor classes PM_2.5 concentrations were measured using two DUSTTRAK direct-reading instruments. Additional class status information was also recorded; concurrently, urban PM_2.5 concentrations and meteorological data were obtained from the fixed monitoring stations and Meteorological Organization. Then, the predicted concentrations of the indoor PM_2.5, from introduced multiple linear regression model via SPSS, compared with the nearest urban air pollution monitoring stations data.Findings: The average outdoor PM_2.5 concentration (43 ± 0.32 µg m⁻³) was higher than the mean indoor (32 ± 0. 21 µg m⁻³), and both were significantly (p < 0.001) surpassing the 24-h EPA standard level. The indoor PM_2.5 concentrations had the highest level in the autumn (48.7 µg m⁻³) and significantly correlated with the outdoor PM_2.5 (r = 0.94, p < 0.001), the number of pupils, ambient temperature, wind speed, wind direction and open area of the doors and windows (p < 0.001). These parameters, as the main determinants, have led to present a 7-variable regression model, with R² = 0.705, which can predict PM_2.5 concentrations in the pre-school classes with more than 80% accuracy. It can be presumed that the penetration of outdoor PM_2.5 was the main source of indoor PM_2.5 concentrations.Research limitations/implications: This study faced several limitations, such as accessibility to classrooms, and limitations in technicians' numbers, leading to researchers monitoring indoor and outdoor PM concentrations in schools once a week. Additionally, regarding logistical limitations to using monitoring instruments in pre-schools simultaneously, correction factors by running the instruments were applied to obtain comparable measurements.Originality/value: The author hereby declares that this submission is his own work and to the best of its knowledge it contains no materials previously published or written by another person.

Purpose Nowadays, noise pollution is considered a major environmental problem which has affected the health and comfort of millions of people around the world. Solving the mentioned problems need to design a new generation of acoustic barriers. Acoustics experts believe that stopping and absorbing the low-frequency sound is difficult. The aims of this study were to remove the harmful frequency in industries and cities. This study concentrates on the reduction of the noise level and increasing the mass law and resonance at low frequencies. Methods Sound measurement and frequency analysis did to fix the harmful frequency in the Shiraz city and in the Shiraz Gas Power Plant. COMSOL 5.3a software used for simulation. Suitable material chose for the manufacture of the sound barrier through the Cambridge engineering selection software 2013. The meta-material sound barrier made and tested in the acoustic room and in the free space. Results analyzed and optimized by Design of Experiment (DOE) and Response Surface Methodology (RSM) software. Mini Tab. 18.1 software used for Statistical Calculations. New sound barriers manufactured with adding new strategies to previous studies to improve the performance of meta-materials like beautification inspired from the flowers of nature and increasing of resonance in internal pipes. Results Three mechanisms used in this scatterer model which included, resonance phenomenon, Band Gap (BG) without absorption mechanism and inner-fractal-like structure. Our technique showed an advantage to reduce at frequencies below 100 Hz without adsorbent usage. The results showed that reduced noise exposures about 17.8 dB at frequency 50 Hz, about 9.1 dB within the range of 250 Hz according to EN 1793–2 standard (Lab Test for Airborne Sound Insulation). The sound barrier reported in this work provides the best and updated solution in the field of noise control. Conclusions A novel generation of sound barriers introduced. We called this structure Interior Quasi-Fractal Sonic Crystal Acoustic Barrier (IQFSCAB). In this study, several different gaps used to remove various frequencies. It could be concluded that the outcomes of the meta-material models based on the Sonic Crystal (SC) could be used for the purpose of noise control system and could be helpful for decision-makers on the noise control legislations. Interaction of waves with noise barriers and wave propagation inside periodic media is a hot topic in many branches of science and technology. The acoustic metamaterial can create green environments by reducing the low frequencies of industrial noise or traffic jam. New barrier have added a number of new strategies to previous studies in order to improve the performance of meta-materials. Our technique shows a clear advantage over to absorb at frequencies below 100 Hz without adsorbent usage. Innovative use of several different gaps and diameters for to remove various frequencies was done in this study. We called this structure IQFSACB due to fractal like interior pipes as those seen in some of the flowers in nature.

There is a wide range of resources for CO₂ emissions. The net amount of CO₂ emissions in the cement industry due to the consumption of fossil fuels and the chemical processes of cement production under heating raw materials is reported to be in the range of 15–25%; this industry, among all the industries and after the power plants and refineries, is the largest CO₂ gas producer throughout the world. Using CO₂ capture and storage (CCS), it can reduce greenhouse gas emissions in a short time. In this study, the technical feasibility study of recycling CO₂ in Abyek Cement Company, with a cement production capacity of about 12,500 tons per day in two production lines, has been studied as one of the largest cement industries throughout the world. Fuel oil (Mazut) is used as the primary fuel for furnaces in this industry. Affected by combustion, the emissions emitted from the five-stage preheater contain 5/24% vol% of CO₂, 7.6% H₂O, 4.8% vol% of O₂, and 63.1% N₂.

The goal of this study was to investigate the ambient concentrations and dispersion patterns of SO₂ originating from a gas refinery located in Asaluyeh, Iran, to determine the refinery’s contribution in emitting SO₂ in the region and also to assess SO₂-associated health risks in the study area. First, SO₂ emissions from the stacks and ambient SO₂ concentrations at 10 receptors in and around the refinery were measured from summer 2014 to spring 2015 using a Testo 350XL analyzer and a portable device (LSI-Lastem Babuc A). The amounts of SO₂ concentrations due to flaring were also calculated using the emission factors. Then ambient concentrations and dispersion patterns of SO₂ in the study area at 1-hr, 24-hr, and annual mean values were simulated on a scale of 10×10 km², using an AERMOD model. Moreover, a non-carcinogenic risk assessment was performed using a U.S. Environmental Protection Agency procedure. The results indicated that about 64% of ambient SO₂ concentrations were due to this refinery and the remaining concentrations were due to contributions from neighboring sources. The values of maximum simulated ambient SO₂ concentrations at average periods of 1-hr, 24-hr, and annual for the scale of 10×10 km² were 24,588, 1,366.1, and 498 μg/m³, respectively, which were higher than the U.S. EPA standard limits. There was also a potential health risk for short-term exposure (HQ = 1.4), but in long-term exposure an acceptable level of concentration (HQ = 0.28) was created.

The positive matrix factorization is a powerful environmental analysis technique which has been successfully utilized to assess air-born particulate matter