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Objective and Background: Among air pollutants, particles are the primary and major pollutant. Research conducted by World Health Organization (WHO) shows that per each 10 micrograms increase in the concentration of particles, the mortality rate rises 1 to 3 times. The purpose of this study has been to determine the concentration of PM2.5 and determinants of it distribution in Tehran’s metro stations is autumn and winter of 2012. Materials and Methods: In this study, concentrations of PM2.5 in 24 of Tehran’s metro stations were measured during autumn and winter. At each station, samples were taken in 4 spots and 4 times: morning, afternoon, evening and night. For sampling of particles, a portable real-time reading particle monitoring device HAZ DUST EPAM 5000 with a flow of 4 liters per minute was used. Results from measurements were compared with EPA and DOE (Department of Environment) standards. Results: The results showed that max, average and min concentrations of PM2.5 in underground stations were 103, 49 and 10 µg/m3 respectively, also max, average and min concentration PM2.5 at ground-level stations were 99, 39 and 8 µg/m3 respectively. Conclusion: The results of this study indicate that the average concentration of suspended particles in Tehran metro stations was higher than EPA and DOE environment standards and air quality in metro stations was inappropriate.

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Background and purpose: Heavy metals in urban air are major health threats and increase the risk of respiratory, cardiovascular, and cancers in humans. An efficient and low-cost method for monitoring these pollutants is using tree bark as a bioindicator. The purpose of this study was to measure the concentration of heavy metals by pine tree bark as a bioindicator in Neishabur, north-east of Iran and the ecological risk of these pollutants.
Materials and methods: Twenty seven locations were determined on Neishabour map using GIS. Concentrations of heavy metals, including silver (Ag), arsenic (As), cobalt (Co), cesium (Cs), manganese (Mn), lead (Pb), copper (Cu), zinc (Zn), chromium (Cr), and cadmium (Cd) were measured using Inductivity Coupled Plasma-Mass Spectrometry. Ecological risk potential index, total ecological risk, and Spearman correlation coefficient were examined.
Results: In this study, Cr and Zn had the highest average concentrations (34.7 mg/kg and 10.2 mg/kg,respectively) and other heavy metals in the bark were in the following order: Mn>Cu>Co>Pb>As>Ag>Cd>Cs. The average ecological risk potential decreases as Cd>As>Pb>Zn>Cu>Cr. Ecological risk potential index for all heavy metals except As and Cd (medium risk) was found to be at low-risk levels. The total ecological risk index showed that the concentrations of the studied heavy metals are at low-risk levels. Spearman correlation analysis showed that Cs and As had the highest correlation among the elements and there is a considerable relationship between these heavy metals which indicates the same source of pollution. Cr and Cd also have a strong correlation and have the same source of contamination.
Conclusion: The present study showed low risk of heavy metal pollution according to the average ecological risk potential in pine bark samples in Neishabour.