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Background: Particle matter is a major air pollutant and an increase of 10 µg/m3 in its concentration may cause an increase of 1-3% in the mortality rate. The aim of this study was to determine the concentration of the PM10 air pollutant in the city of Khorramabad. Methods: This is a cross-sectional study. The experiments were conducted during one year, from April 2010 to March 2011, using a dust track analyzer. The data were analyzed by conducting one-way ANOVA, and Scheffé's multiple comparison method, and then compared with the Environment Protection Organization__AWT_QUOTE__s standard rates. Findings: The results revealed that the maximum concentrations of PM10 and PM2.5 were, respectively, 120.9 and 101.09 µ/m3 at Shamshirabad station. There was a significant difference between the mean values of PM10 and PM2.5 concentrations (µg/m3) during the different seasons. In addition, the mean concentrations of PM10 exceeded the maximum permissible concentration in warmer months. Conclusion: An annual comparison of PM10 and PM2.5 concentrations with the standard revealed that particle matter concentration was higher than the standard during the summer season. However, the total mean of particle matter was less than the standard concentration.

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Background: Among the chemical pollutants present in wastewater, heavy metals are persistent compounds the toxicity of which on biological wastewater processes, humans, and the environment has been proven in various studies. In this study, the half maximal effective concentration (EC50) of growth inhibition of cadmium, lead, and mercury was assessed on dominant bacterial species present in sequencing batch reactors (SBR).Methods: Biomass sample was obtained from the biological unit of the SBR established in Moorchekhort Industrial Settlement, Isfahan, Iran. After cultivation and isolation of the dominant bacterial species, their DNA was sequenced through polymerase chain reaction (PCR) technique and the bacteria species were determined. After exposure of these bacteria to different concentrations of mercury, cadmium, and lead, their EC50 was determined using resazurin bioassay.Findings: Aeromonas, Pseudomonas, Bacillus, and Enterobacter were registered as the 4 dominant bacterial species in the SBR. A great difference was observed in the sensitivity of these 4 bacteria to the heavy metals. Pseudomonas was the most sensitive bacteria to cadmium and lead, while Aeromonas was the most sensitive specie to lead.Conclusion: It can be concluded that Aeromonas and Pseudomonas are suitable bioindicators for toxicity assessment of wastewater and effluents contaminated with heavy metals.

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Background: The entrance of toxic compounds into wastewater treatment plants (WWTPs) can induce disorder in their biological units. Therefore, it is necessary to determine the sources of toxic wastewaters. In this study, the toxicity of the wastewater of 3 metal plating industries was assessed using sequencing batch reactor (SBR) bacteria.Methods: To obtain the 1-1000 ml/l concentrations, the 3 metal plating wastewater solutions were diluted using distilled water. To determine the growth inhibition in each concentration, the 0.5 cc cultured SBR bacteria on nutrient broth media was used and cultured on nutrient agar media. Data were analyzed using the Probit analysis in SPSS software and the 50% effective concentration (EC50) was calculated.Findings: According to the Probit analysis, there was no effect on the tested bacteria at the concentrations of 1 ml/l, less than 50 ml/l, and less than 100 ml/l of metal plating wastewater in samples 1, 2, and 3, respectively. However, all studied bacterial species were eliminated in the concentration of 1000 ml/l of each metal plating wastewater. Maximum and minimum EC50 were recorded for the metal plating wastewater sample number 3 (960 ml/l) and number 1 (6.5 ml/l), respectively.Conclusion: Results of this study showed that some metal plating wastewaters, even in very low concentrations, can induce adverse effects on the bacterial community structures of biological units of WWTPs. Thus, it is recommended that effluent standards and in situ treatment rules be applied according to the performed process type in such industries.