Determination of the concentrations and the chemical composition of particulate matter in the North Aegean region
Particulate matter (PM) pollution is a major environmental problem in urban and remote areas, as it causes adverse effects upon human health and affects directly or indirectly the climate of the Earth. PM can vary considerably in size, chemical composition and origin. Therefore, numerous studies hav...
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| Κύριοι συγγραφείς: | , |
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| Άλλοι συγγραφείς: | |
| Γλώσσα: | English |
| Δημοσίευση: |
2022
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| Θέματα: | |
| Διαθέσιμο Online: | http://hdl.handle.net/11610/23176 |
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| Περίληψη: | Particulate matter (PM) pollution is a major environmental problem in urban and remote areas, as it causes adverse effects upon human health and affects directly or indirectly the climate of the Earth. PM can vary considerably in size, chemical composition and origin. Therefore, numerous studies have investigated particle pollution exposure and its effects around the globe, including the region of the Eastern Mediterranean, which is considered a climate change hotspot that is affected by transportation of air pollutants originating from Europe, Africa and Asia. Despite these studies, however, there is still insufficient information on the air quality of insular coastal areas on the northern part of Eastern Mediterranean, i.e., the Northern Aegean Sea (NAS), and on the contribution of the local and the distant sources that influence it.
The objective of this thesis is to estimate the physical-chemical properties of PM in urban and suburban-background sites in the NAS region and to compare them with those of other regions. First, it provides background information for PM10 concentration levels in the two major urban centres in Greece, namely Athens and Thessaloniki over the period 2001 to 2010. Results indicate that most of the urban and suburban stations in these two major urban centres exhibit high PM10 concentrations and exceed the EU annual and 24-h limits during the entire period. However, PM10 levels at urban and suburban stations are lower compared to other European and US cities of the same size. With the exception of the suburban stations in Athens and one station in Thessaloniki, all others had highest and the lowest monthly average PM10 concentrations during the autumn/winter and the summer months, respectively. For the suburban stations in Athens, the highest values are observed during the spring and the lowest during the winter, while one station in Thessaloniki did not exhibit any seasonality due to its proximity to an industrial zone.
Second, this thesis reports PM measurements at urban and remote sites in the NAS region. Measurements of atmospheric aerosol particles conducted at a remote site of NAS in summer under representative synoptic meteorological conditions (i.e., Etesian wind conditions) showed that long-range transportation of air pollutants from industrial and urban environments can significantly affect the quality of the air in remote regions. When strong northeastern winds prevail, the air masses pass over the wider Istanbul region. This result to a shift of the peak particle size from 100 to 20 nm, while an up to a six-fold increase in particle number concentration and high particle values of growth rates (ca. 9.0 nm h-1) are observed. An additional indication that particles observed in the region of NAS are long range transported from urban and/or industrial areas is provided the increased values of sulfates and nitrates, and the OC/EC ratio during the days of particle transportation compared to the rest of the sampling period.
The characteristics of atmospheric aerosol particles and the potential PM sources in an urban measurement site in the NAS region were investigated during the warm and cold periods. Mean PM2.0 and PM1.0 concentrations at the city centre were lower compared to corresponding values from large cities in the region. Higher average mass and number concentrations were observed in winter compared to summer, due to the additional emissions from domestic heating and the weaker atmospheric dilution. During both seasons, however, PM emissions related to local natural and anthropogenic sources. The elemental composition measurements also showed that natural sources contribute sea-salt and re-suspended soil to the PM load in the city’s atmosphere. Non-exhaust traffic emission sources were also found to be important, while a strong contribution from local traffic sources was also identified by the increased number concentrations in the Aitken mode during rush hours. In addition to these sources, long-range transported pollution mainly from Northeastern Turkey enriched the collected particle samples with crustal and anthropogenic elements (i.e., K, Ca, Ti, Mg, Fe, As, S), contributing to the decline of air quality in the region of NAS.
Finally, this thesis evaluates the discrepancy between beta attenuation (BAM) and gravimetric (GM) measurements at a suburban site in the study region, taking into account the effect of factors such as the meteorological conditions and the type of filter material on the PM measurements. An overestimation of the ВАM measurements, which was ~30% for the PM2.5 and ~10% for the PM10 data, was observed. Discrepancies between BAM and GM PM2.5 measurements increased with: a.) increasing available water vapor, suggesting that the aerosol-bound water has a strong effect on the measurements, b.) the use of highly hydrophobic Teflon filters to the GM method when the atmospheric water vapor pressure increased, and c.) the potential availability of the volatility or stability in the aerosol phase when species such as ammonium nitrate were present. Better correlation between GM and BAM measurements was observed during the cold rather than the warm period and when GM samples were collected on filters made of glass fiber, which is incidentally the material of the BAM filter tape. The finding from this study can be used for the better interpretation of PM measurements conducted with various BAM monitors. |
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