10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Investigation of the Morphology and Chemical Composition of Intra-Urban Atmospheric Particles: Case Study of Tehran, Iran
Balal Oroji, Asghar Sadighzadeh, Eisa Solgi, HOSSEIN YOUSEFI, Nuclear Science and Technology Research Institute, Iran
Abstract Number: 51 Working Group: Aerosol Physics
Abstract Nowadays, air pollution in cities with regard to its harmful outcomes has been turned into one of the serious challenges in urban management and Tehran city, one of the most polluted cities in the world. As the air pollutant gasesُ concentration is being influenced by environmental factors, the probability of pollution will not be uniform across Tehran. The work described the use of Scanning Electron Microscopy (SEM) combined with X¬-ray Dispersive Energy Spectrometry (EDS) to characterize inorganic atmospheric particles samples collected on PM10 filters from June to October 2017 from five zones within the city of Tehran. Given the wind direction in the region, the particles produced in the urban areas move to the east and north-east during most of the autumn. These particles grow at the time of displacement when dealing with a single-rod and are eliminated with increasing weight when dealing with different levels. Due to the nature of these particles and their subterranean nature, the risk of inhaling particles in the center of the area to the east of the region is more than other areas. The elemental composition of these particles indicates that C, O and Si rich particles were dominant. The other dominated elements were Zn, Ca and Al. This could be inferred as the fly ash origin. These particles can be related to originate from construction activity, regional transport from the urban zones as well as agricultural vegetative burning and natural dust. These particles are composed primarily of feldspar (Ca, Si, Al) and clay (Al, Fe, Si), their origin is mainly crustal, but they can also come from erosion of building products and road dust. Our results indicate that in autumn and winter, the air quality at Tehran is often influenced by regional air pollution as shown by spatial distribution of PM10 concentration. It is found that PM10 had almost the same concentration in regional background air and in different types of urban environments. The special meteorological conditions and the role of regional-scale transport can explain why local abatements in cities cannot lead to significant improvement of the air quality during smog events. These particles morphology and chemical composition, illustrate an abundance of natural elements within the zone. However, some of the elements presented are directly related with human activities, and are of much interest from the public health and environmental perspectives. Due to atmospheric conditions in the region, the suspended particles in the atmosphere are divided into two major groups: urban particles that are the result of combustion of fossil fuels in the region. In the second group, resources are generated outside of the urban boundaries and in the marginal areas of the study area, which mainly consist of particles from dust storms, biomass, as well as moving and fixed resources. Land use change in the western regions of the region and the conversion of vegetation cover and rangelands to residential and industrial areas is the main reason for the production of pollutants in these areas. The shape of these particles is irregular due to the origin of the mineral and due to the presence of biomass particles; they are regular and sometimes spherical forms. Carbon and silica are mainly found in the composition of these particles.