The study of the air quality index of Isfahan city and the thermodynamic and synoptic analysis of the critical days of 1395

 
The air pollution phenomenon in the last few years after Zayandehrud drying was the second environmental problem in Isfahan, which was the result of population growth, urbanization expansion, transport development, increased industrial activity and fuel consumption
The study of the status of air quality in Isfahan's meteorological station in 1395 indicates that 32 days of clean air (9%), 243 days of healthy weather (66%), 62 days of unhealthy for Sensitive groups (17%) and 29 unhealthy days The general public (8%).
By comparing different pollutants in this year, it was found that particulate matter with a diameter of less than 2.5 microns with an unfavorable condition for 85 days are the main pollutant of this station.
During the year 95, the highest quality index was released on Aban 25th, reaching 176, the pollutant responsible for PM2.5 this day, with a mean concentration of 24 hours to 103 micrograms.
The cleanest day was 95, 1st and 2nd of Azar with a 29th index every two days. In 86% (316 days) since 1395, pollutant particles with a diameter smaller than 2.5 microns were the responsible pollutant
8% (29 days) of the days of the year, the responsible pollutant, ozone to the surface of the earth and pollutant nitrogen dioxide
 at 6% (22 days) has been responsible since 1395 as pollutant.
The most infected days occurred in the days of Dey (20 days), Aban (15 days) and Azar (13 days), respectively.
The study of maximum concentrations of atmospheric pollutants, such as suspended particles with a diameter of less than 2.5 microns (PM2.5), sulfur dioxide (SO2), nitrogen dioxide (NO2) and carbon monoxide (CO), indicates that In November 1395 concentration of atmospheric pollutants was higher than in other months of the year, In the 9-day period, from 19 to 27 Aban, the highest quality indicator was shown.
In this paper, there was a statistical-thermodynamic study on this period.
The results of this study indicate that The stability of air and subsidence in the middle layers of the atmosphere due to the rule of anticyclines systems, the reduction of temperature and the increase of air pressure on the surface,arrival of thermodynamic indicators to the boundary of stability and its passing, Radiation inversion and its sustainability in a few consecutive days, especially in cold seasons, Due to the topography of Isfahan and industrial centers, it helps to increase the potential for accumulation of pollutants and to increase the air quality index.