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Assessment of Sources and Components of Fine PM and Effect of Different Parameters on them in Tehran

Zare Shahneh, Maryam | 2019

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 52568 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Arhami, Mohammad
  7. Abstract:
  8. Currently PM2.5 is a major air pollution concern in Tehran, Iran due to frequent high levels and possible adverse impacts. In this study, which is the first of its kind to take place in Tehran, composition and sources of PM2.5 and carbonaceous aerosol were determined, and their seasonal trends were studied. In this regard, fine PM samples were collected every six days at four station for two years from February 2014 to February 2015 (first phase) and March 2015 to February 2016 (second phase). The samples were analyzed for ions, organic carbon (including water-soluble and insoluble portions), elemental carbon (EC), and all detectable elements. The source apportionment was performed using organic molecular marker-based CMB receptor modeling. Carbonaceous compounds were the major contributors to fine particulate mass in Tehran, as OC and EC together comprised for first and second sampling durations on average 29% and 26% of PM2.5 mass. Major portions of OC in Tehran were water insoluble and are mainly attributed to primary sources. Higher levels of several PAHs, which are organic tracers of incomplete combustion, and hopanes and steranes as organic tracers of mobile sources were obtained in cold months and compared to the warm months. The contributions of different components varied considerably throughout the year, particularly the dust component that varied from 7% in the cold season to 56% in the hot and dry season. Principal component analyses were applied, resulting in 5 major source factors that explained 85% of the variance in fine PM. Factor 1, representing soil dust, explained 53%; Factor 2 denotes heavy and toxic metals mainly found in industrial sources and accounted for 18%; and rest of factors, mainly representing combustion sources, explained 14% of the variation. The levels of major toxic metals were further evaluated, and their trends showed considerable increases during cold seasons.The major contributing source to particulate OC was identified as vehicles, which contributed about 72% of measured OC in first phase. Among mobile sources, gasoline-fueled vehicles had the highest impact with a mean contribution of 48% to the measured OC. Mobile sources also were the largest contributor to total PM2.5 (first phase 40%, second phase 20%), followed by dust (24%, 32%) and sulfate (11%, 11%). In addition to primary emissions, mobile sources also directly and indirectly played an important role in another part of fine particulate mass (secondary organics and ions), which highlights the impact of vehicles in Tehran. Our results highlighted and quantified the role of motor vehicles in fine PM production, particularly during winter time. The results of this study could be used to set more effective regulations and control strategies particularly upon mobile sources. So, sampling campaign in Niyayesh tunnel was applied in order to determine the gasoline exhaust profile in Tehran. By using the new source profile for gasoline vehicle, the contribution of this source was changed from 24% to 30% and the mean contribution of mobile source didn’t change significantly. Hence, these results suggest that organic compounds profiles from vehicular emissions are not significantly influenced by the geographic area.PM induced reactive oxygen species (ROS) production, a for PM toxicity was measured both with an acellular dithiothreitol consumption assay (DTT-ROS; ranged from 2.1 to 9.3 nmoles min−1m−3) and an in vitro macrophage-mediated ROS production assay (AM-ROS; ranged from 125 to 1213 μg Zymosan equivalentsm−3) for the first phase. PM-induced DTT-ROS and AM-ROS were substantially higher for the colder months' PM (1.5-fold & 3-fold, respectively) compared with warm season. Vehicular emission tracers, aliphatic diacids, and hopanes exhibited moderate correlation with ROS measures. Gasoline vehicles and residual oil combustion were moderately associated with both ROS measures (R≥0.67, p < 0.05), while diesel vehicles exhibited a strong correlation with secreted TNF-α in the cold season (R=0.89, p < 0.05)
  9. Keywords:
  10. Sources Apportionment ; Toxicity ; Air Particulate Matter ; Chemical Analysis ; Receptor Model Chemical Mass Balance (CMB) ; Tehran City ; Particulate Matter Less than 2.5 mm

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