Study of the importance of quaternary dust sources emission on Qom air quality

1-Interoduction: Air pollution has been considered as one of the global challenges. According to world health organization (WHO), dust particles are the 5th most dangerous cause of death 4.2 million in the world. According to the world meteorological organization (WMO), when the wind speed increases more than 15 m/s and the visibility decreases because of dust particles less than 1 km, it is called a dust storm. Considering the potential impact of dusts around the city of Qom, it is possible to influence the impact of dust storms on the extent of these centers and their contribution to the air quality of the city of Qom in the aftermath of a storm of dust. The dust storms that affect Qom are originated from two local and transitional emission sources. The main objectives of this study were identification of the main quaternary geological structures as emission sources of dust storms, study dust storms paths and determine the important emission sources that are affect Qom air quality. 2-Material and methods: Initially, dust storms were detected using dust codes and verification of MODIS images during the period 2008 to 2017. Remote sensing is a suitable method for detecting dustborne events and has recently been successfully used to understand the location of dust sources.   The position of geological formations at the site of the focal points indicates that the bed of most of the focal points is from quaternary deposits. The Quaternary geological period is the fourth and final period of geology, and most of the constituent parts of these centers, including the ancient coniferous terraces and clay alluvial tundra, are prone to dust production. This study were trajectory using HYSPLIT model and orientation index (windrose, dust rose and CPF). In order to investigate the wind condition as one of the most important factors in dust storms, windrose and dust rose were used using WRPLOT software. One of the common ways to identify the geographic direction of dust sources is the CPF function. The CPF examines the potential of any direction in the transfer of pollutants, especially particulate matter released from a source in which the wind is greater than the specified threshold. The HYSPLIT model is one of the most practical methods for determining the duct movement, dispersion and dip galvanizing simulationThe model of the propagation algorithm was identified for each occurrence and was investigated at three altitudes of 10, 500 and 1000 m in backward for 24 hours for local Events and 72 hours for transitional Events. 3-Results and discussion: Out of 531 identified events, after verification by dust codes and MODIS images, 400 events were detected in Qom between 2008 and 2017 years about 84 percent of the incidents occurred in the spring and summer. The results of windrose and dust rose indicate that east and west directions have the highest wind direction in Qom, which are differents in different seasons, and the results of windrose are more similar to the seasonal results of summer and spring, the occurrence of most events in two seasons spring and Summer shows. Seasonal CPF results with slightly different windrose and dust rose results, show the northwest and east directions in the spring and summer, and northwest in the autumn and winter seasons. Due Because of the CPF shows the potential for dust production and most of the events occurred in the spring and summer season, the results of the windrose spring and summer and dust rose were similar and confirm the occurrence of this dust numbers in the two seasons of spring and summer In these directions. The results of HYSPLIT At three altitudes of 10, 500 and 1000 meters in the period from 2008 to 2017 in Qom Due Because of the two altitudes of 1000 and 500 meters are far away from the phenomena and topographic changes of the Earth, they have little effect on the dusts. Dust routing results at 10 m elevation were studied. The results of trajectiries the HYSPLIT model at 10 m elevation in the study period in Qom show that the most important directions of dust entering the city of Qom, Like the results of wind rose, dust rose and CPF, it is east, southeast, west, and southwest, who There are many events in the east and south-east of the west and southwest, and From these directions, there is no significant dusting in the southwest direction around the city of Qom, and in other directions there are many dusty centers. Investigating the frequency and direction of the dust storm trajectory occurring in Qom during the studied period shows that the most important centers dust that affect the air quality of Qom city, where the threat of more events has passed, Respectively, the centers of numbers 4, 10, 11 and 2 are located among these centers, centers numbers 4, 10 and 11 in the direction of east and south-east of the city of QomThe center number 2 is located west of the city of Qom, and this direction was also Is important recognized by the results of wind rose, dust rose and CPF. Also, the results of the HYSPLIT model trajectory for transitional dusts Which has influenced the city of Qom during the studied period, shows that most of these dusts from the country are than Iraq, then Syria and Saudi Arabia. 4-Conclusion There are several dusts centers around the city of Qom. Among these centers, the center of number 4 (the distance between salt lake and Houz-e-Sultan), located east of Qom, is due to the close distance, high area, the genus of the formation and, most importantly, the abundance The passage of events from this center, which includes the largest number, and centers of numbers 10, 11 and 2 too After the center of number 4, is the most important and most influential source of dust on the city of Qom relative to other centers.