Iranian Journal of

Background and Objective: The aim of this study was to investigate dust origin particulate (PM_2.5) in Mashhad city in a long period of time (2014-2019) based on unhealthy days. Furthermore, changes in meteorological parameters and their relationship with dust storms have also been investigated.
Materials and Methods: In order to locate dust pollution hotspots in mashhad air, first, information about unhealthy days of Mashhad city in a 5-year period was obtained from the site of Mashhad Pollutants Monitoring Center and then HYSPLIT model was used to locate air pollution hotspots caused by particulate matter. To verify the results, the outputs obtained from this model were also compared with the DREAM8b model.
Results: By examining the meteorological parameters and its relationship with the outputs obtained from THEHYSPLIT and DREAM8b models, the maximum wind speed and relative humidity were obtained in autumn. There was no rainfall in the studied days (19 days) and the highest temperature was related to summer, indicating the relationship between the occurrences of polluted days due to particulate matter less than μ 2.5, wind speed and relative humidity in autumn. The results of the two models showed that the southern and northeastern regions of Mashhad city had the highest source of dust particles during the studied days.
Conclusion:  Although in previous articles, the origin of dust in Mashhad city was announced outside the geographical boundaries of the province, long-term investigation at low altitude (below 10m) showed that local origin of dust have an essential role in air pollution in Mashhad city under unstable atmospheric conditions. Inappropriate use of agricultural lands and severe changes in land use often in the northern region and implementation of construction projects such as the southern belt of Mashhad city play essential roles in increasing PM_2.5 particles in the air of Mashhad. This finding shows the importance of decision making for the implementation of soil stabilization projects etc... at the local level.

Background and Objective: The city of Tehran is always exposed to adverse consequences due to the establishment of various sources of heavy metals. Therefore, the purpose of this study is to identify the types of heavy metals in airborne particles and the origin of heavy metals in the 21st district of Tehran.
Materials and Methods: According to the EPA standard, 5 stations from District 21 of Tehran were selected for sampling. Using the ASTM D4096 method and using a high volume sampling pump, 50 samples of total airborne particles were collected. The samples were transferred to the laboratory and the concentration of heavy metals was measured by ICP-OES. The UNMIX source model was used to identify heavy metal sources.
Results: The average concentration of heavy metals in 1400 is a decreasing trend including Li according to the concentration of heavy metals in the air in the SPECIATE database, the role of light vehicle sources was 47 percent 34 percent on the street and 18 percent at the airport.
Conclusion: The source of light vehicles exhibited the highest share of emissions and the element aluminum showed the highest concentration among heavy metals in Region 21. Therefore, the UNMIX source model can correctly identify index elements and priority sources for contaminant control.