121. Development and evaluation of an improved offline aerosol mass spectrometry techniqueChristina Vasilakopoulou, Kalliopi Florou, Christos Kaltsonoudis, Iasonas Stavroulas, Nikolaos Mihalopoulos, Spyros N. Pandis, 2023, izvirni znanstveni članek Opis: Abstract. The offline aerosol mass spectrometry technique is
a useful tool for the source apportionment of organic aerosol (OA) in areas
and periods during which an aerosol mass spectrometer (AMS) is not available. However, the technique is
based on the extraction of aerosol samples in water, while several
atmospheric OA components are partially or fully insoluble in water. In this work an improved offline technique was developed and evaluated in an effort to capture most of the partially soluble and insoluble organic aerosol material, reducing significantly the uncertainty of the corresponding source
apportionment. A major advantage of the proposed approach is that no
corrections are needed for the offline analysis to account for the limited
water solubility of some OA components. The improved offline AMS analysis
was tested in three campaigns: two during winter and one during summer.
Collocated online AMS measurements were performed for the evaluation of the offline method. Source apportionment analysis was performed separately for the online and the offline measurements using positive matrix
factorization (PMF). The PMF results showed that the fractional contribution of each factor to the total OA differed between the online and the offline PMF results by less than 15 %. The differences in the AMS spectra of the
factors of the two approaches could be significant, suggesting that the use
of factor profiles from the literature in the offline analysis may lead to
complications. Part of the good agreement between the online and the
offline PMF results is due to the ability of the improved offline AMS
technique to capture a bigger part of the OA, including insoluble organic
material. This was evident by the significant fraction of submicrometer
suspended insoluble particles present in the water extract and by the
reduced insoluble material on the filters after the extraction process. More than half of the elemental carbon (EC) was on average missing from the
filters after the water extraction. Significant EC concentrations were
measured in the produced aerosol that was used as input to the AMS during
the offline analysis. Ključne besede: organic aerosol, receptor modeling, offline PMF, Greece Objavljeno v RUNG: 10.05.2024; Ogledov: 306; Prenosov: 2 Povezava na datoteko Gradivo ima več datotek! Več... |
122. Ambient carbonaceous aerosol levels in Cyprus and the role of pollution transport from the Middle EastAliki Christodoulou, Iasonas Stavroulas, Mihalis Vrekoussis, Maximillien Desservettaz, Michael Pikridas, Elie Bimenyimana, Jonilda Kushta, Matic Ivančič, Martin Rigler, Philippe Goloub, 2023, izvirni znanstveni članek Opis: Abstract. The geographical origin and source apportionment of submicron carbonaceous aerosols (organic aerosols, OAs, and black carbon, BC) have been investigated here for the first time, deploying high time-resolution measurements at an urban background site of Nicosia, the capital
city of Cyprus, in the eastern Mediterranean. This study covers a half-year
period, encompassing both the cold and warm periods with continuous
observations of the physical and chemical properties of PM1 performed
with an Aerosol Chemical Speciation Monitor (ACSM), an aethalometer,
accompanied by a suite of various ancillary offline and online measurements. Carbonaceous aerosols were dominant during both seasons (cold and warm periods), with a contribution of 57 % and 48 % to PM1, respectively, and exhibited recurrent intense nighttime peaks (> 20–30 µg m−3) during the cold period, associated with local domestic heating. The findings of this study show that high concentrations of sulfate (close to 3 µg m−3) were continuously recorded, standing among the highest ever reported for Europe and originating from the Middle East region. Source apportionment of the OA and BC fractions was performed using the
positive matrix factorization (PMF) approach and the combination of two
models (aethalometer model and multilinear regression), respectively. Our
study revealed elevated hydrocarbon-like organic aerosol (HOA)
concentrations in Nicosia (among the highest reported for a European urban
background site), originating from a mixture of local and regional
fossil fuel combustion sources. Although air masses from the Middle East had
a low occurrence and were observed mostly during the cold period, they were
shown to strongly affect the mean concentrations levels of BC and OA in
Nicosia during both seasons. Overall, the present study brings to our
attention the need to further characterize primary and secondary
carbonaceous aerosols in the Middle East, an undersampled region
characterized by continuously increasing fossil fuel (oil and gas) emissions
and extreme environmental conditions, which can contribute to photochemical
ageing. Ključne besede: PM1, BC, source apportionment, Cyprus, long range transport Objavljeno v RUNG: 10.05.2024; Ogledov: 286; Prenosov: 2 Celotno besedilo (5,55 MB) Gradivo ima več datotek! Več... |
123. Impact of peri-urban forest fires on air quality and aerosol optical and chemical properties : the case of the August 2021 wildfires in Athens, GreeceDimitris G. Kaskaoutis, Kalliopi Petrinoli, Georgios Grivas, Panayiotis Kalkavouras, M. Tsagkaraki, Kyriaki Papoutsidaki, Iasonas Stavroulas, D. Paraskevopoulou, Aikaterini Bougiatioti, 2024, izvirni znanstveni članek Ključne besede: biomass burning, carbonaceous aerosols, scattering, absorption, chemical composition, Mediterranean Objavljeno v RUNG: 10.05.2024; Ogledov: 298; Prenosov: 0 Gradivo ima več datotek! Več... |
124. Intra- and inter-city variability of ▫$PM_2.5$▫ concentrations in Greece as determined with a low-cost sensor networkKonstantinos Dimitriou, Iasonas Stavroulas, Georgios Grivas, Charalampos Chatzidiakos, Georgios Kosmopoulos, Andreas Kazantzidis, Konstantinos Kourtidis, Athanasios Karagioras, Nikolaos Hatzianastassiou, Spyros N. Pandis, 2023, izvirni znanstveni članek Opis: Measurements of PM2.5 concentrations in five major Greek cities over a two-year period using calibrated low-cost sensor-based particulate matter (PM) monitors (Purple Air PA-II) were combined with local meteorological parameters, synoptic patterns and air mass residence time models to investigate the factors controlling PM2.5 spatiotemporal variability over continental Greece. Fourteen sensors nodes in Athens, Patras, Ioannina, Xanthi, and Thermi (in the Metropolitan Area of Thessaloniki) were selected out of more than 100 of a countrywide network for detailed analysis. The cities have populations ranging from 65k to 3M inhabitants and cover different latitudes along the South-North axis. High correlations between the daily average PM2.5 levels were observed among all sites, indicating strong intra- and inter-city covariance of concentrations, both in cold and warm periods. Higher PM2.5 concentrations in all cities during the cold period were primarily associated with low temperatures and stagnant anticyclonic conditions, favoring the entrapment of residential heating emissions from biomass burning. Anticyclonic conditions were also connected to an increased frequency of PM2.5 episodes, exceeding the updated daily guideline value (15 μg m−3) of the World Health Organization (WHO). During the warm period, nearly uniform PM2.5 levels were encountered across continental Greece, independently of their population size. This uniformity strongly suggests the importance of long-range transport and regional secondary aerosol formation for PM2.5 during this period. Peak concentrations were associated mainly with regional northern air flows over Greece and the Balkan Peninsula. The use of the measurements from dense air quality sensor networks, provided that a robust calibration protocol and continuous data quality assurance practices are followed, appears to be an efficient tool to gain insights on the levels and variability of PM2.5 concentrations, underpinning the characterization of spatial and seasonal particularities and supporting real-time public information and warning. Ključne besede: particulate matter, PM2.5, biomass burning, low-cost sensors, purple air PA-II, concentration weighted trajectory, potential source contribution function Objavljeno v RUNG: 10.05.2024; Ogledov: 325; Prenosov: 2 Povezava na datoteko Gradivo ima več datotek! Več... |
125. Regional new particle formation over the Eastern Mediterranean and Middle EastPanayiotis Kalkavouras, Aikaterini Bougiatioti, Tareq Hussein, Nikos Kalivitis, Iasonas Stavroulas, Panagiotis Michalopoulos, Nikolaos Mihalopoulos, 2021, izvirni znanstveni članek Opis: Atmospheric new particle formation (NPF) events taking place over large distances between locations, featuring similar characteristics, have been the focus of studies during the last decade. The exact mechanism which triggers NPF still remains indefinable, so are the circumstances under which simultaneous occurrence of such events take place in different environments, let alone in environments which are parted by over 1200 km. In this study, concurrent number size distribution measurements were conducted in the urban environments of Athens (Greece) and Amman (Jordan) as well as the regional background site of Finokalia, Crete, all located within a distance of almost 1300 km for a 6-month period (February–July 2017). During the study period Athens and Finokalia had similar occurrence of NPF (around 20%), while the occurrence in Amman was double. When focusing on the dynamic characteristics at each site, it occurs that formation and growth rates at Amman are similar to those at Finokalia, while lower values in Athens can be ascribed to a higher pre-existing particle number at this urban site. By comparing common NPF events there are 5 concomitant days between all three sites, highly related to air masses origin. Additionally, for another 19 days NPF takes place simultaneously between Finokalia and Amman, which also share common meteorological characteristics, adding to a total of 60% out of 41 NPF events observed at Finokalia, also simultaneously occurring in Amman. Ključne besede: NPF, Eastern Mediterranean, particle number size distributions, concurrent regional events Objavljeno v RUNG: 10.05.2024; Ogledov: 360; Prenosov: 3 Celotno besedilo (5,07 MB) Gradivo ima več datotek! Več... |
126. Cooking as an organic aerosol source leading to urban air quality degradationIasonas Stavroulas, Aikaterini Bougiatioti, Georgios Grivas, Eleni Liakakou, Kalliopi Petrinoli, Konstantinos Kourtidis, Evangelos Gerasopoulos, Nikolaos Mihalopoulos, 2024, izvirni znanstveni članek Ključne besede: ACSM, PMF, cooking organic aerosol, meat charbroiling Objavljeno v RUNG: 10.05.2024; Ogledov: 320; Prenosov: 0 Gradivo ima več datotek! Več... |
127. Foods2012 Ključne besede: food sciences and technology, food chemistry and physical properties, food engineering and production, food security and safety, food toxicology, sensory and food quality, food analysis, functional foods, food and health, food psychology, food and environment Objavljeno v RUNG: 10.05.2024; Ogledov: 376; Prenosov: 1 Povezava na datoteko Gradivo ima več datotek! Več... |
128. Vertical profiling of fresh biomass burning aerosol optical properties over the Greek urban city of Ioannina, during the PANACEA winter campaignChristina-Anna Papanikolaou, Alexandros Papayannis, M. Mylonaki, Romanos Foskinis, Panagiotis Kokkalis, Eleni Liakakou, Iasonas Stavroulas, O. Soupiona, Nikolaos Hatzianastassiou, Maria Gavrouzou, 2022, izvirni znanstveni članek Opis: Vertical profiling of aerosol particles was performed during the PANhellenic infrastructure for Atmospheric Composition and climatE chAnge (PANACEA) winter campaign (10 January 2020–7 February 2020) over the city of Ioannina, Greece (39.65° N, 20.85° E, 500 m a.s.l.). The middle-sized city of Ioannina suffers from wintertime air pollution episodes due to biomass burning (BB) domestic heating activities. The lidar technique was applied during the PANACEA winter campaign on Ioannina city, to fill the gap of knowledge of the spatio-temporal evolution of the vertical mixing of the particles occurring during these winter-time air pollution episodes. During this campaign the mobile single-wavelength (532 nm) depolarization Aerosol lIdAr System (AIAS) was used to measure the spatio-temporal evolution of the aerosols’ vertical profiles within the Planetary Boundary Layer (PBL) and the lower free troposphere (LFT; up to 4 km height a.s.l.). AIAS performed almost continuous lidar measurements from morning to late evening hours (typically from 07:00 to 19:00 UTC), under cloud-free conditions, to provide the vertical profiles of the aerosol backscatter coefficient (baer) and the particle linear depolarization ratio (PLDR), both at 532 nm. In this study we emphasized on the vertical profiling of very fresh (~hours) biomass burning (BB) particles originating from local domestic heating activities in the area. In total, 33 out of 34 aerosol layers in the lower free troposphere were characterized as fresh biomass burning ones of local origin, showing a mean particle linear depolarization value of 0.04 ± 0.02 with a range of 0.01 to 0.09 (532 nm) in a height region 1.21–2.23 km a.s.l. To corroborate our findings, we used in situ data, particulate matter (PM) concentrations (PM2.5) from a particulate sensor located close to our station, and the total black carbon (BC) concentrations along with the respective contribution of the fossil fuel (BCff) and biomass/wood burning (BCwb) from the Aethalometer. The PM2.5 mass concentrations ranged from 5.6 to 175.7 μg/m3, while the wood burning emissions from residential heating were increasing during the evening hours, with decreasing temperatures. The BCwb concentrations ranged from 0.5 to 17.5 μg/m3, with an extremely high mean contribution of BCwb equal to 85.4%, which in some cases during night-time reached up to 100% during the studied period. Ključne besede: lidar, depolarization ratio, fresh biomass burning aerosols, domestic heating, black carbon, PM2.5 Objavljeno v RUNG: 10.05.2024; Ogledov: 319; Prenosov: 3 Celotno besedilo (6,36 MB) Gradivo ima več datotek! Več... |
129. Source apportionment of fine and ultrafine particle number concentrations in a major city of the Eastern MediterraneanPanayiotis Kalkavouras, Georgios Grivas, Iasonas Stavroulas, Kalliopi Petrinoli, Aikaterini Bougiatioti, Eleni Liakakou, Evangelos Gerasopoulos, Nikolaos Mihalopoulos, 2024, izvirni znanstveni članek Ključne besede: UFP, PNSD, receptor modelling, lockdown, Athens Objavljeno v RUNG: 10.05.2024; Ogledov: 351; Prenosov: 0 Gradivo ima več datotek! Več... |
130. The effect of the averaging period for PMF analysis of aerosol mass spectrometer measurements during offline applicationsChristina Vasilakopoulou, Iasonas Stavroulas, Nikolaos Mihalopoulos, Spyros N. Pandis, 2022, izvirni znanstveni članek Opis: Offline aerosol mass spectrometer (AMS) measurements can
provide valuable information about ambient organic aerosols in areas and
periods in which online AMS measurements are not available. However, these
offline measurements have a low temporal resolution, as they are based on
filter samples usually collected over 24 h. In this study, we examine
whether and how this low time resolution affects source apportionment
results. We used a five-month period (November 2016–March 2017) of online
measurements in Athens, Greece, and performed positive matrix factorization (PMF)
analysis to both the original dataset, which consists of 30 min
measurements, and to time averages from 1 up to 24 h. The 30 min results
indicated that five factors were able to represent the ambient organic
aerosol (OA): a biomass burning organic aerosol factor (BBOA), which contributed
16 % of the total OA; hydrocarbon-like OA (HOA) (29 %); cooking OA (COA) (20 %); more-oxygenated OA (MO-OOA) (18 %); and less-oxygenated OA (LO-OOA) (17 %). Use of the daily averages resulted in estimated average contributions that were within 8 % of the total OA compared with the high-resolution analysis for the five-month period. The most important difference was for the BBOA contribution, which was overestimated (25 % for low resolution versus 17 % for high resolution) when daily averages were used. The estimated secondary OA varied from 35 % to 28 % when the averaging
interval varied between 30 min and 24 h. The high-resolution results are
expected to be more accurate, both because they are based on much larger
datasets and because they are based on additional information about the
temporal source variability. The error for the low-resolution analysis was
much higher for individual days, and its results for high-concentration days in particular are quite uncertain. The low-resolution analysis
introduces errors in the determined AMS profiles for the BBOA and LO-OOA
factors but determines the rest relatively accurately (theta angle around
10∘ or less). Ključne besede: AMS, offline PMF, ACSM, organic aerosols Objavljeno v RUNG: 10.05.2024; Ogledov: 376; Prenosov: 3 Celotno besedilo (3,75 MB) Gradivo ima več datotek! Več... |