نوع مقاله : مقاله کامل
1 عضو هیئت علمی دانشگاه زنجان
2 دانشجوی دکترای آب و هواشناسی دانشگاه زنجان
عنوان مقاله [English]
Neglecting the environment in recent years has caused many environmental problems. The Extensive development of cities and urbanization, the growth of industrial sector, especially in the vicinity of large cities and combining them with a range of natural and climatic factors, increase the air pollution and change the urban environments, and some of the globalized ones, so the environment gets out of balance and seriously damage and it has raised human concerns for the future. The most important problems of the last two decades are greenhouse gas emissions and global warming.
Air pollution is one of the major environmental and economic problems that have emerged around the world and this issue, especially in large industrial cities, is a more acute problem. It can be said that air pollution has started since the invention of fire. When Industrialization reached the forefront of development, urban climate and air quality changed dramatically, leading to changes in the hydrological cycle, agriculture, irregular rainfall, as well as increasing drought and floods.
The weather conditions on each day are affected by the synoptic conditions prevailing in each region on that day. In other words, it is due to the arrangement of atmospheric systems in relation to each other and the dynamic and thermodynamic properties that govern them. Therefore, the synoptic pattern is sometimes such that the conditions of stability and calm prevail in the atmosphere, and as a result, due to the density of pollutants in the lower layers and lack of atmospheric currents or their weak intensity, the intensity of pollution and increased. Synopticity is such that it makes the atmosphere unstable and due to the intensification of vertical and horizontal currents, contaminants are spread inside the atmosphere and its concentration decreases.
As mentioned above , Air pollution is a significant issue, especially in metropolitan areas. The atmospheric conditions and the air types of the cities are the factors that aggravate this problem. Tabriz metropolis faces severe air pollution. The main objective of this study is to investigate the relation between atmospheric conditions and the air type of the Tabriz city in the intensification of air pollutants.
Materials and methods
Three types of data are used in this study, including: a) the mean of the hourly data of atmospheric pollutants, b) the mean of the daily weather data to extract air types, and c) atmospheric data to study atmospheric patterns of air types.
The weather type of Tabriz city was clustered based on the Euclidean distance and with the integration method "Ward". Accordingly, for the day's selection, the representative will be selected the day most closely resembling the group's maximum number of days. Then, using daily atmospheric data (including sunshine hours, dew point temperature, minimum visibility, average cloudy, average vapor pressure, average wind speed, station pressure, sea level pressure, rainfall, average temperature, average minimum temperature, average maximum Temperature, mean relative humidity, mean relative humidity and average maximum relative humidity) at Tabriz station, the relationship between air pollution and pollution in Tabriz city was investigated.
Results and discussion
Trial and error, applying the mid-group and outsourced type tests, it was revealed that the three weather types were prevalent in Tabriz during the study period. Representative days were extracted from 3 weather types.
Regarding PM10 pollutants and air types, it was found that days with a hazardous state of concern for PM10 have occurred in type 2. For this reason, three days with low, moderate and dangerous pollution were extracted from PM10 in type 2. The days of the representative of the three brigades were as follows:
weather types 1: 29/3/2004, weather types 2: 3/4/2004, 15/4/2005 (For PM10 with low pollution), 28/11/2005 (For PM10 with moderate pollution) and 6/5/2009 ( In terms of PM10 with high contamination (and type 3: 14/4/2004)
By investigating atmospheric variables and atmospheric pollutants, it was found that the amount of air pollution is more related to wind speed and direction. The winds are low in winter, but there are plenty of swings in this season from the southwest and west. Most of the major industries in the city of Tabriz are in the west of the city, which winds the west of suspended particles into the city, and the Ainal and Zinalal mountains in the northeast of the city function as a barrier against the wind stream, and the suspended. wind carried particles to the The city. In the winter, there is a reversal that intensifies pollution and concentration in the city and reduces its transmission to other parts.
The results of the survey of air types associated with infected days show the dominant wind direction in these days is from southwest, northeast with a relatively low speed which is the result of the deployment of two high-pressure centers of Europe and Siberia in the northwest and northeast of Iran and one low-pressure center on the Caspian Sea. As a result, the movement of air from high-pressure areas to the low-pressure zone in the clockwise direction has led to the development of south-west flows. On the days when the PM10 pollutant has reached its highest level, in the 1000-HP level a low-pressure center and in the 500-HP orbital flow is dominant in the study area. The wind of sea-level and the 500-HP were from southwest and west. Since the industries and factories of Tabriz city are located in the west side of the city, the mentioned low-pressure in connection with adjacent systems leads particles and industrial pollution to the center of the city.
Most of the major industries of the city such as thermal power plant, petrochemical complex, refinery etc. are located in the west of the city.
Tabriz is surrounded by rough terrain and is located in a valley where pollutants cannot spread easily and sometimes condense on top of the area. Winds from the west bring suspended particles to the city, and the Aynal and Zinal Mountains in the northeast of the city serve as a barrier against wind currents and suspended particles carried by the wind over the city.
The provisional nature of suspended particulate contamination confirms the existence of a temporary diffusion factor, namely the wind factor, so there is a direct relationship between the increase in air and wind particulate matter from the southwest of Tabriz.