مهندسی عمران شریف (Feb 2022)
Source apportionment of fine particulate matter using combined receptor models in Tehran
Abstract
Currently, one of the most important air pollutants in Tehran is fine particulate matter. The composition and sources of these particles are poorly known; therefore, in order to distinguish the status of PM2.5 pollutants from their chemical compounds, 24-hour PM2.5 samples were collected at the main residential station (an Air Quality Control Company site, located in Sharif University of Technology) every six days for a full year from February 2014 to February 2015. The samples were analyzed for ions, organic carbon (including water-soluble and insoluble portions), Elemental Carbon (EC), and all detectable elements. Based on the results of chemical analyses including TOT, GCMS, IC, SF-ICPMS, and ROS methods, Organic Matter (OM) is one of the most important compounds in PM2.5, which on average constitutes 35% of the mass of fine particulate matter. The contribution of PM2.5 sources was determined by the CMB model using the concentration of chemical components of the particles and the profile of possible sources in Tehran. According to previous results, mobile sources (such as gasoline, diesel, and smoking vehicles) as the most important source of particulate matter, accounting for 58% of the total concentration of PM2.5. Road dust, the second significant source contribution, was described as the first loading factor, accounting for 49% of the changes in particle concentration extracted by running the PCA model. Combined model (principal component analysis/multiple linear regression chemical mass balance; PCA/MLR+CMB) comprising two stages has been developed for improving the accuracy of identifying PM2.5 sources. The results show that the second factor of the PCA model including 17% of PM changes is a composite source, and it is influenced by heavy metals from human resources including industries, car brakes, car tires, and car lubricating oils and, in this factor, combustion. Heavy fuels with an average of 65.10% made the largest contribution to the emission of particulate matter associated to factor 2. The insights regarding fine PM in Tehran provided by the results of this paper could be useful in planning effective control strategies and decision-making in Tehran, Iran.
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