Supervisors info:
Φλόκα Έλενα, Καθηγήτρια, τμήμα Φυσικής / τομέας Φυσικής Περιβάλλοντος-Μετεωρολογίας, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Summary:
The objective of this study, is to investigate the role of meteorology in the dispersion of fine particulate matter (PM 2.5) in the greater Piraeus area, as well as to identify possible sources of such particles. The study was performed in collaboration with the National Center for Scientific Research "Demokritos", that provided the data based on measurements carried out at three sites in the greater area of Piraeus from February to October 2019.
Because synoptic scale air circulation plays an important role in air quality, pollutant transport, and consequently, human discomfort and health, a classification was performed based on the Kassomenos et al (1997) scheme, which provides for eight summary categories at the isobaric surface of 850 hPa. The classification was applied for each day of the experimental period for the wider region of Attica and then a statistical comparison is made of the frequency of occurrence of each category in each month of the experimental period in relation to the corresponding period 1983-2019, in order to investigate the representativeness of meteorological conditions prevailed during the experimental period. It was found that the experimental period was characterized by a significant increase in the frequency of cyclonic systems, associated with rain and a corresponding decrease in anti-cyclonic systems, associated with clear weather and drought. In addition, July and August were characterized by a significant decrease in etesians (meltemia).
Subsequently the source apportionment technique was employed, which is essentially a statistical method based on the principle of conservation of mass in order to group the measurements in possible sources of pollutants and to estimate the contribution of each source to the total concentrations of fine particulate matter. Using the PMF model, 7 sources / groups of sources are identified in the area. These are related to: Industrial Activities with 17% contribution, Secondarily formed suspended particles (nitrates) with 9% contribution, Ship Emissions and Port Activities with 11% contribution, Dust resuspension from the ground and Road surfaces with 13% , Secondarily formed suspended particles (sulfates) with a contribution of 24%, Emissions of vehicles (cars and heavy vehicles) with a contribution of 21% and Natural Marine Emissions (sea salt) with a contribution of 5%.
Finally, after selecting the days where the seven factors show their maximum values as they were extracted from the PMF model, maps are studied at the isobaric surface of 850hPa, 500hPa and 300hPa. It was found that the 56% of the days prevail Warm Advection (WA) associated with downward movements and temperature increase in the lower atmosphere and at the same time strengthening of the ridge / weakening of the trough in the upper layers. Also, a Positive Vorticity Advection (PVA) prevails in the vast majority of the days associated with upward movements in the atmosphere and at the same time convergence and pressure drop at the surface being related with the passage of the jet stream and the existence of a trough.
Keywords:
PMF , PM2.5 , particulate matter , synoptic scale classification
