91. |
92. On-flight intercomparison of three miniature aerosol absorption sensors using unmanned aerial systems (UASs)Michael Pikridas, Spiros Bezantakos, Griša Močnik, Christos Keleshis, Fred Brechtel, Iasonas Stavroulas, Gregoris Demetriades, Panayiota Antoniou, Panagiotis Vouterakos, Marios Argyrides, 2019, izvirni znanstveni članek Opis: The present study investigates and compares the ground and in-flight
performance of three miniaturized aerosol absorption sensors integrated
on board small-sized Unmanned Aerial Systems (UASs). These sensors were
evaluated during two contrasted field campaigns performed at an urban site,
impacted mainly by local traffic and domestic wood burning sources (Athens,
Greece), and at a remote regional background site, impacted by long-range
transported sources including dust (Cyprus Atmospheric Observatory, Agia
Marina Xyliatou, Cyprus). The miniaturized sensors were first intercompared at the ground-level
against two commercially available instruments used as a reference. The
measured signal of the miniaturized sensors was converted into the
absorption coefficient and equivalent black carbon concentration (eBC). When
applicable, signal saturation corrections were applied, following the
suggestions of the manufacturers. The aerosol absorption sensors exhibited
similar behavior against the reference instruments during the two campaigns,
despite the diversity of the aerosol origin, chemical composition, sources,
and concentration levels. The deviation from the reference during both
campaigns concerning (eBC) mass was less than 8 %, while for the absorption
coefficient it was at least 15 %. This indicates that those sensors that
report black carbon mass are tuned and corrected to measure eBC more accurately than the absorption coefficient. The overall potential use of miniature aerosol absorption sensors on board
small UASs is also illustrated. UAS-based absorption measurements were used
to investigate the vertical distribution of eBC over Athens up to 1 km above
sea level during January 2016, exceeding the top of the planetary boundary
layer (PBL). Our results reveal a heterogeneous boundary layer concentration
of absorbing aerosol within the PBL intensified in the early morning hours
due to the concurrent peak traffic emissions at ground-level and the fast
development of the boundary layer. After the full development of the PBL,
homogenous concentrations are observed from 100 m a.g.l. to the PBL top. Ključne besede: Unmanned Aerial Systems, Cyprus Atmospheric Observatory, eBC, vertical profiling, microaethalometer Objavljeno v RUNG: 13.05.2024; Ogledov: 314; Prenosov: 1 Povezava na datoteko |
93. Anarchism and the history of social movements in SloveniaDaša Tepina, 2021, izvirni znanstveni članek Opis: The article is a compilation of fragments of revolutionary movements in the Slovenian region,
which in one way or another were connected to or derived from the tradition of anarchist ideas and
practises. It is an overview of an omnipresent phenomenon that
never had or has never had a broader
social visibility, but was always present in the shadows and on the margins, continuously shaping
social movements and communities in revolt and offering refuge to many marginalised and oppressed
people, thus amplifying
their voice, which gradually changed the general social conditions. A modest
overview, supplemented by archival sources from the Slovenian archives and newspaper articles from
different periods. It covers a wide area of the fragmented 20th century, touchi
ng at the end on the
transition to the 21st century. So even it is difficult to argue that there is a history of the anarchist
movement in this region, that can be described as a rooted, consistent anarchist history, and it takes a
certain spirit of enquir
y to discover and bring to the surface anarchist ideas and practises, we,
however, can talk about fragments of historical events and groups that were connected and
intertwined with anarchist ideas in various practices connected with anarchist principles. A
nd all of
them were inherent for an organized anarchist movement, which was established in the last three
decades that we can speak today of an overtly coherent set of ideas and practises. Ključne besede: anarchism, Slovenia, history of social movements, anarchist ideas, anarchist practices Objavljeno v RUNG: 13.05.2024; Ogledov: 408; Prenosov: 5 Celotno besedilo (100,54 KB) Gradivo ima več datotek! Več... |
94. Nocturnal boundary layer turbulence regimes analysis during the BLLAST campaignJesús Yus-Díez, Mireia Udina, Maria Rosa Soler, Marie Lothon, Erik Nilsson, Joan Bech, Jielun Sun, 2019, izvirni znanstveni članek Opis: A night-time turbulence regime classification, the so-called “HOckey-Stick Transition ” (HOST) theory, proposed by Sun et al. (2012) from the Cooperative Atmosphere–Surface Exchange Study-1999 (CASES-99) is explored using data from the Boundary-Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign which took place during summer 2011 in the central French Pyrenean foothills. Results show that the HOST turbulence relationships for the BLLAST field campaign data are strongly dependent on both the meteorological and orographic features. The HOST pattern only appears for nights when a stably stratified boundary layer can be developed, corresponding to fair-weather and clear-sky nights, when the flow is generated by the nearby orography, from the south and the south-east. Those flows strongly influenced by the orography may generate intermittent or enhanced turbulence. When considering the whole nocturnal dataset for these flow directions, several enhanced turbulence points are found to be associated with sudden wind speed and directional shear transitions. In contrast, flows from other directions do not reproduce the HOST relationships and the turbulence relationship is almost linear, independent of vertical temperature gradients, corresponding to flows driven by synoptic scales. In addition we identify examples of gravity waves and top-down turbulent events that lead to transitions between the turbulence regimes. Ključne besede: air turbulence, BLLAST campaign Objavljeno v RUNG: 13.05.2024; Ogledov: 346; Prenosov: 3 Celotno besedilo (6,60 MB) Gradivo ima več datotek! Več... |
95. Emission of volatile organic compounds from residential biomass burning and their rapid chemical transformationsMaximillien Desservettaz, Michael Pikridas, Iasonas Stavroulas, Aikaterini Bougiatioti, Eleni Liakakou, Nikolaos Hatzianastassiou, Jean Sciare, Nikolaos Mihalopoulos, Efstratios Bourtsoukidis, 2023, izvirni znanstveni članek Opis: Biomass combustion releases a complex array of Volatile Organic Compounds (VOCs) that pose significant challenges to air quality and human health. Although biomass burning has been extensively studied at ecosystem levels, understanding the atmospheric transformation and impact on air quality of emissions in urban environments remains challenging due to complex sources and burning materials. In this study, we investigate the VOC emission rates and atmospheric chemical processing of predominantly wood burning emissions in a small urban centre in Greece. Ioannina is situated in a valley within the Dinaric Alps and experiences intense atmospheric pollution accumulation during winter due to its topography and high wood burning activity. During pollution event days, the ambient mixing ratios of key VOC species were found to be similar to those reported for major urban centres worldwide. Positive matrix factorisation (PMF) analysis revealed that biomass burning was the dominant emission source (>50 %), representing two thirds of OH reactivity, which indicates a highly reactive atmospheric mixture. Calculated OH reactivity ranges from 5 s−1 to an unprecedented 278 s−1, and averages at 93 ± 66 s−1 at 9 PM, indicating the presence of exceptionally reactive VOCs. The highly pronounced photochemical formation of organic acids coincided with the formation of ozone, highlighting the significance of secondary formation of pollutants in poorly ventilated urban areas. Our findings underscore the pressing need to transition from wood burning to environmentally friendly sources of energy in poorly ventilated urban areas, in order to improve air quality and safeguard public health. Ključne besede: biomass burning, urban air quality, VOCs, emission factors, source apportionment Objavljeno v RUNG: 13.05.2024; Ogledov: 387; Prenosov: 1 Celotno besedilo (8,93 MB) |
96. Insights into the single-particle composition, size, mixing state, and aspect ratio of freshly emitted mineral dust from field measurements in the Moroccan Sahara using electron microscopyAgnesh Panta, Konrad Kandler, Andrés Alastuey, Cristina González-Flórez, Adolfo Gonzalez-Romero, Martina Klose, Xavier Querol, Cristina Reche, Jesús Yus-Díez, Carlos Pérez García-Pando, 2023, izvirni znanstveni članek Opis: Abstract. The chemical and morphological properties of mineral dust aerosols emitted by wind erosion from arid and semi-arid regions influence climate, ocean, and land ecosystems; air quality; and multiple socio-economic sectors. However, there is an incomplete understanding of the emitted dust particle size distribution (PSD) in terms of its constituent minerals that typically result from the fragmentation of soil aggregates during wind erosion. The emitted dust PSD affects the duration of particle transport and thus each mineral's global distribution, along with its specific effect upon climate. This lack of understanding is largely due to the scarcity of relevant in situ measurements in dust sources. To advance our understanding of the physicochemical properties of the emitted dust PSD, we present insights into the elemental composition and morphology of individual dust particles collected during the FRontiers in dust minerAloGical coMposition and its Effects upoN climaTe (FRAGMENT) field campaign in the Moroccan Sahara in September 2019. We analyzed more than 300 000 freshly emitted individual particles by performing offline analysis in the laboratory using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectrometry (EDX). Eight major particle-type classes were identified with clay minerals making up the majority of the analyzed particles both by number and mass, followed by quartz, whereas carbonates and feldspar contributed to a lesser extent. We provide an exhaustive analysis of the PSD and potential mixing state of different particle types, focusing largely on iron-rich (Fe oxide-hydroxides) and feldspar particles, which are key to the effects of dust upon radiation and clouds, respectively. Nearly pure or externally mixed Fe oxide-hydroxides are present mostly in diameters smaller than 2 µm, with the highest fraction below 1 µm at about 3.75 % abundance by mass. Fe oxide-hydroxides tend to be increasingly internally mixed with other minerals, especially clays, as particle size increases; i.e., the volume fraction of Fe oxide-hydroxides in aggregates decreases with particle size. Pure (externally mixed) feldspar represented 3.2 % of all the particles by mass, of which we estimated about a 10th to be K-feldspar. The externally mixed total feldspar and K-feldspar abundances are relatively invariant with particle size, in contrast to the increasing abundance of feldspar-like (internally mixed) aggregates with particle size with mass fractions ranging from 5 % to 18 %. We also found that overall the median aspect ratio is rather constant across particle size and mineral groups, although we obtain slightly higher aspect ratios for internally mixed particles. The detailed information on the composition of freshly emitted individual dust particles and quantitative analysis of their mixing state presented here can be used to constrain climate models including mineral species in their representation of the dust cycle. Ključne besede: mineral dust, Moroccan Sahara, electron microscopy Objavljeno v RUNG: 13.05.2024; Ogledov: 360; Prenosov: 3 Celotno besedilo (7,13 MB) Gradivo ima več datotek! Več... |
97. Yearlong variability of oxidative potential of particulate matter in an urban Mediterranean environmentD. Paraskevopoulou, Aikaterini Bougiatioti, Iasonas Stavroulas, T. Fang, Maria Lianou, Eleni Liakakou, Evangelos Gerasopoulos, R. Weber, Athanasios Nenes, Nikolaos Mihalopoulos, 2019, izvirni znanstveni članek Opis: The oxidative potential (OP) of fine and coarse fractions of ambient aerosols was studied in the urban environment of Athens, Greece. OP was quantified using a dithiothreitol (DTT) assay, applied to the water soluble fraction of aerosol that was extracted from 361 fine and 84 coarse mode of 24-h and 12-h filter samples over a one-year period. During the cold period, samples were collected on a 12-h basis, to assess the impact of night-time biomass burning emissions from domestic heating on OP. The chemical characteristics of aerosols were measured in parallel using an Aerosol Chemical Speciation Monitoring (ACSM) and a 7-wavelength Aethalometer. A source apportionment analysis on the ACSM data resulted in the identification of organic aerosol (OA) factors on a seasonal basis. A good correlation of OP with NO3−, NH4+, BC (Black Carbon), Organics and LV-OOA (low volatility oxygenated OA) was found during winter, revealing the importance of combustion and aging processes for OP. During the summertime, a good correlation between OP and SO4−2 and NH4+indicates its association with regional aerosol – thus the importance of oxidative aging that reduces its association with any characteristic source. Multiple regression analysis during winter revealed that highly oxygenated secondary aerosol (LV-OOA) and, to a lesser extent, fresh biomass burning (BBOA) and fossil fuel (HOA) organic aerosol, are the prime contributors to the OP of fine aerosol, with extrinsic toxicities of 54 ± 22 pmol min−1 μg−1, 28 ± 7 and 17 ± 4 pmol min−1μg−1, respectively. In summer, OP cannot be attributed to any of the identified components and corresponds to a background aerosol value. In winter however, the regression model can reproduce satisfactorily the water soluble DTT activity of fine aerosol, providing a unique equation for the estimation of aerosol OP in an urban Mediterranean environment. Ključne besede: oxidative potential, reactive oxygen species, DTT assay, particulate matter, urban aerosol Objavljeno v RUNG: 13.05.2024; Ogledov: 342; Prenosov: 0 Gradivo ima več datotek! Več... |
98. Changes in black carbon emissions over Europe due to COVID-19 lockdownsNikolaos Evangeliou, Stephen M. Platt, Sabine Eckhardt, Cathrine Lund Myhre, Paolo Laj, L. Alados-Arboledas, John Backman, Benjamin T. Brem, Markus Fiebig, Jesús Yus-Díez, 2021, izvirni znanstveni članek Opis: Abstract. Following the emergence of the severe acute respiratory syndrome coronavirus
2 (SARS-CoV-2) responsible for COVID-19 in December 2019 in Wuhan (China)
and its spread to the rest of the world, the World Health Organization
declared a global pandemic in March 2020. Without effective treatment in the
initial pandemic phase, social distancing and mandatory quarantines were
introduced as the only available preventative measure. In contrast to the
detrimental societal impacts, air quality improved in all countries in which
strict lockdowns were applied, due to lower pollutant emissions. Here we
investigate the effects of the COVID-19 lockdowns in Europe on ambient black
carbon (BC), which affects climate and damages health, using in situ
observations from 17 European stations in a Bayesian inversion framework. BC
emissions declined by 23 kt in Europe (20 % in Italy, 40 % in Germany,
34 % in Spain, 22 % in France) during lockdowns compared to the same
period in the previous 5 years, which is partially attributed to COVID-19
measures. BC temporal variation in the countries enduring the most drastic
restrictions showed the most distinct lockdown impacts. Increased particle
light absorption in the beginning of the lockdown, confirmed by assimilated
satellite and remote sensing data, suggests residential combustion was the
dominant BC source. Accordingly, in central and Eastern Europe, which
experienced lower than average temperatures, BC was elevated compared to the
previous 5 years. Nevertheless, an average decrease of 11 % was seen
for the whole of Europe compared to the start of the lockdown period, with
the highest peaks in France (42 %), Germany (21 %), UK (13 %), Spain
(11 %) and Italy (8 %). Such a decrease was not seen in the previous
years, which also confirms the impact of COVID-19 on the European emissions
of BC. Ključne besede: black carbon, covid-19, emissions, Europe Objavljeno v RUNG: 13.05.2024; Ogledov: 387; Prenosov: 3 Celotno besedilo (11,03 MB) Gradivo ima več datotek! Več... |
99. Summertime particulate matter and its composition in GreeceM. A. Tsiflikiotou, E. Kostenidou, D. K. Papanastasiou, D. Patoulias, Pavlos Zarmpas, D. Paraskevopoulou, E. Diapouli, Christos Kaltsonoudis, Kalliopi Florou, Iasonas Stavroulas, 2019, izvirni znanstveni članek Opis: During the summer of 2012 a coordinated field campaign was conducted in multiple locations in Greece in order to characterize the ambient particulate matter (PM) levels, its chemical composition and the contribution of the regional and local sources. PM1, PM2.5 and PM10 samples were collected simultaneously at seven different sites in Greece: an urban and a suburban station in Patras, a suburban station in Thessaloniki, a suburban and an urban background station in Athens, a rural background station at the Navarino Environmental Observatory (NEO) in southwestern Peloponnese and a remote background site at Finokalia in the northeastern part of Crete. The sites were selected to facilitate the estimation of the contribution of the local emission sources and long range transport.
Sulfate and organics were the major PM1 components in all sites suggesting that high sulfate levels still remain in parts of Europe. The photochemistry of the Eastern Mediterranean can convert rapidly the emitted sulphur dioxide to sulfate. Our analysis indicated significant sulfate production over the area, with high sulfate levels, especially in the remote site of Finokalia, associated with air masses that had passed over Turkey. There was high regional secondary organic aerosol production dominating organic aerosol levels even in a major city like Athens. High organic aerosol levels were associated with air masses that had crossed the Balkans with a significant biogenic component. The average PM2.5 concentration ranged from 13 to 18 μg m−3 in the different sites. There were unexpected significant gradients in the concentrations of secondary aerosol components in length scales of a few hundred kilometers. The low concentrations of measured PM2.5 nitrate are mostly organic nitrates and supermicrometer nitrate associated with sea-salt and dust. Dust was a significant PM10 constituent in all areas and was quite variable in space showing the importance of the local sources. Ključne besede: PM2.5, sulfate aerosol, secondary inorganic aerosol, secondary organic aerosol, Greece Objavljeno v RUNG: 13.05.2024; Ogledov: 336; Prenosov: 0 Gradivo ima več datotek! Več... |
100. Sources and processes that control the submicron organic aerosol composition in an urban Mediterranean environment (Athens) : a high temporal-resolution chemical composition measurement studyIasonas Stavroulas, Aikaterini Bougiatioti, Georgios Grivas, D. Paraskevopoulou, M. Tsagkaraki, Pavlos Zarmpas, Eleni Liakakou, Evangelos Gerasopoulos, Nikolaos Mihalopoulos, 2019, izvirni znanstveni članek Opis: Submicron aerosol chemical composition was studied during a year-long
period (26 July 2016–31 July 2017) and two wintertime intensive campaigns
(18 December 2013–21 February 2014 and 23 December 2015–17 February 2016),
at a central site in Athens, Greece, using an Aerosol Chemical Speciation
Monitor (ACSM). Concurrent measurements included a particle-into-liquid
sampler (PILS-IC), a scanning mobility particle sizer (SMPS), an AE-33
Aethalometer, and ion chromatography analysis on 24 or 12 h filter samples.
The aim of the study was to characterize the seasonal variability of the main
submicron aerosol constituents and decipher the sources of organic aerosol
(OA). Organics were found to contribute almost half of the submicron mass,
with 30 min resolution concentrations during wintertime reaching up to
200 µg m−3. During winter (all three campaigns combined),
primary sources contributed about 33 % of the organic fraction, and comprised
biomass burning (10 %), fossil fuel combustion (13 %), and cooking
(10 %), while the remaining 67 % was attributed to secondary aerosol.
The semi-volatile component of the oxidized organic aerosol (SV-OOA;
22 %) was found to be clearly linked to combustion sources, in
particular biomass burning; part of the very oxidized,
low-volatility component (LV-OOA; 44 %) could also be attributed to the
oxidation of emissions from these primary combustion sources. These results, based on the combined contribution of biomass burning organic
aerosol (BBOA) and SV-OOA, indicate the importance of increased biomass
burning in the urban environment of Athens as a result of the economic recession.
During summer, when concentrations of fine aerosols are considerably lower,
more than 80 % of the organic fraction is attributed to secondary aerosol
(SV-OOA 31 % and LV-OOA 53 %). In contrast to winter, SV-OOA appears
to result from a well-mixed type of aerosol that is linked to fast photochemical
processes and the oxidation of primary traffic and biogenic emissions.
Finally, LV-OOA presents a more regional character in summer, owing to the
oxidation of OA over the period of a few days. Ključne besede: ACSM, organic aerosol, PMF, source apportionment Objavljeno v RUNG: 13.05.2024; Ogledov: 327; Prenosov: 2 Celotno besedilo (4,65 MB) Gradivo ima več datotek! Več... |