81. Molekularna karakterizacija lebdećih čestica slobodne troposfere sa Opservatorija Pico planineKatja Džepina, Claudio Mazzoleni, Paulo Fialho, Swarup China, B. Zhang, R. Chris Owen, D. Helmig, J. Hueber, Sumit Kumar, J. A. Perlinger, 2017, published scientific conference contribution abstract Abstract: Long-range transported free tropospheric aerosol was sampled at the PMO (38°28’15’’N, 28°24’14’’W; 2225 m amsl) on Pico Island of the Azores in the North Atlantic. Filter-collected aerosol during summer 2012 was analysed for organic and elemental carbon, and inorganic ions. The average aerosol ambient concentration was 0.9 µg m-3. Organic aerosol contributed the majority of mass (57%), followed by sulphate (21%) and nitrate (17%). Filter-collected aerosol was positively correlated with on-line aerosol measurements of black carbon, light scattering and number concentration. Water-soluble organic compounds (WSOC) from 9/24 and 9/25 samples collected during a pollution event were analysed with ultrahigh-resolution FT-ICR MS. FLEXPART analysis showed the air masses were very aged (>12 days). ~4000 molecular formulas were assigned to each of the mass spectra between m/z 100-1000. The majority of the assigned molecular formulas have unsaturated structures with CHO and CHNO elemental compositions. WSOC have an average O/C of ~0.45, relatively low compared to O/C of other aged aerosol, which might be the result of evaporation and fragmentation during long-range transport. The increase in aerosol loading during 9/24 was linked to biomass burning emissions from North America by FLEXPART and MODIS fire counts. This was confirmed with WSOC biomass burning markers and with the morphology and mixing state of particles as determined by SEM. The presence of markers characteristic of aqueous-phase reactions of biomass burning phenolic species suggests that the aerosol collected at Pico had undergone cloud processing. The air masses on 9/25 were more aged (~15 days) and influenced by marine emissions, as indicated by organosulphates and species characteristic for marine aerosol (e.g. fatty acids). The change in air masses for the two samples was corroborated by the changes in ozone, ethane, propane, morphology of particles, as well as by FLEXPART. In this presentation we will presents the first detailed molecular characterization of free tropospheric aged aerosol intercepted at the PMO.
Keywords: Atmospheric aerosol, Free troposphere, Mass spectrometry, Pico mountain observatory
Published in RUNG: 26.05.2021; Views: 2873; Downloads: 0
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82. Sarajevo Canton Winter Field Campaign 2018 : particulate air pollution in a global hotspotKatja Džepina, Vaios Moschos, Anna Tobler, Francesco Canonaco, Deepika Bhattu, Roberto Casotto, Athanasia Vlachou, Jasna Huremović, Sabina Žero, Griša Močnik, 2020, published scientific conference contribution abstract Abstract: Nowadays, urban centres in countries of the Western Balkan region (including Bosnia and Herzegovina (B&H)) are experiencing some of the poorest European and global air quality due to the extensive use of solid fuels (e.g., wood, coal) and old vehicle fleet. Western Balkan countries lack state-of-the-art atmospheric sciences research despite high levels of ambient pollution, which makes the efforts to understand the mechanisms of their air pollution imperative. The city of Sarajevo, the capital of B&H, is situated in a basin surrounded by mountains. Particularly during the winter months, topography and meteorology cause significant pollution episodes.
The Sarajevo Canton Winter Field Campaign 2018 (SAFICA) took place from Dec 04, 2017 to Mar 15, 2018 with on-line aerosol measurements and collection of daily, continuous filter PM10 samples for off-line laboratory analyses. SAFICA aimed to give the first detailed characterization of the Western Balkans aerosol composition including organic aerosol (OA) to elucidate aerosol emission sources and atmospheric processing and to estimate the adverse health effects. PM10 samples (ntotal=180) were collected at four sites in the Sarajevo Canton: a) Bjelave and b) Pofalići (urban background); c) Otoka (urban); d) Ivan Sedlo (remote). The urban sites were distributed along the city basin to study the pollutants’ urban evolution and the remote site was chosen to compare urban to background air masses.
SAFICA PM10 samples underwent different off-line laboratory chemical analyses: 1) Bulk chemical composition of the total filter-collected water-soluble inorganic and OA by a high-resolution Aerodyne Aerosol Mass Spectrometer (AMS). The measured AMS OA spectra were further analysed by Positive Matrix Factorization (PMF) using the graphical user interface SoFi (Source Finder) to separate OA into subtypes characteristic for OA sources and atmospheric processes. 2) Organic and elemental carbon (OC/EC), water-soluble organic carbon, polycyclic aromatic hydrocarbons, levoglucosan, and 14C content of total carbon to evaluate OA chemical composition. 3) Major inorganic anions and cations to evaluate aerosol inorganic species. 4) Metal content in aerosol determined by two analytical techniques (AAS and ICP-MS). SAFICA on-line measurements of black carbon (Aethalometer) and the particle number concentration (Condensation Particle Counter and Optical Particle Sizer) enabled the insights into the daily evolution of primary pollutants and an assessment of aerosol size and number distribution.
The combined SAFICA results for on- and off-line measurements will be presented. Our results show that the carbon-containing species make ~2/3 of PM10 mass and the majority are oxygenated, water-soluble OA species with an average OM/OC = 1.9 (Fig.1). Urban air pollution crises in the Western Balkan will be put in the context of local, regional and global air quality. Finally, we will present the scientific questions opened by SAFICA, including the advantages and limitations of SAFICA data set, and give the recommendations for future studies.
Keywords: Sarajevo, urban air pollution, PM10, PM2.5
Published in RUNG: 26.05.2021; Views: 2743; Downloads: 20
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83. Opazovanja plimskih raztrganj zvezd z Velikim sinoptičnim pregledovalnim teleskopomKatja Bricman, Andreja Gomboc, 2018, published scientific conference contribution abstract Abstract: Plimska raztrganja zvezd so redki dogodki, do katerih pride, ko zvezdo zanese v bližino masivne črne luknje v središču galaksije, kjer jo močne plimske sile črne luknje raztrgajo. Blišč svetlobe, ki ob tem nastane, lahko opazujemo do kozmoloških razdalj. Veliki sinoptični pregledovalni teleskop (Large Synoptic Survey Telescope - LSST), ki je v gradnji v Čilu, bo ponavljajoče opazoval 18.000 kvadratnih stopinj južnega neba v šestih optičnih filtrih do limitne magnitude 24,5 v r filtru. Omogočal bo opazovanja 20 milijard zvezd in 20 milijard galaksij, s primerjavo starih in novih posnetkov pa bo zaznal spremembe na nebu oziroma tranzientne izvore ter bo tako odlično orodje za iskanje plimskih raztrganj zvezd. Z uporabo simulacijskega orodja LSST smo simulirali opazovanja plimskih raztrganj zvezd na majhnem delu neba velikosti 20,25 kvadratnih stopinj. S pomočjo simuliranih svetlobnih krivulj smo ocenili število plimskih raztrganj zvezd, ki jih bo teleskop odkril v desetih letih delovanja.
Keywords: Plimska raztrganja zvezd, pregledovalni teleskopi
Published in RUNG: 10.05.2021; Views: 2088; Downloads: 0 |
84. Zofka Kveder : Slavic cultural and feminist icon of the early 20th centuryKatja Mihurko, 2021, independent scientific component part or a chapter in a monograph Keywords: Zofka Kveder, slovenska književnost, Martha Tausk, Zdenka Haskova, Avgust Cesarec, Elvira Dolinar, Zdenka Marković, Julka Chlapec-Đorđević, Minka Govekar, Vladimir Jelovšek, Josef Svetopluk Machar
Published in RUNG: 12.04.2021; Views: 2098; Downloads: 57
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85. Long-term ozone data analysisVjera Butković, Tomislav Cvitaš, Katja Džepina, Nenad Kezele, Leo Klasinc, 2002, original scientific article Abstract: Various approaches to the analysis of 10-year continuous ozone monitoring from the EUROTRAC-TOR network station Puntijarka near Zagreb are reported. The site has a rural character (45.90degrees N; 15.97degrees E, 980 m a.s.l.) and is representative of the lower troposphere of a wider region. Mean hourly ozone volume fractions measured from 1990-1999, autocorrelation plots for all data and for data for summer periods (May-Sep.), box and whiskers representations of diurnal variations during winter (Nov.-March) and summer periods, mean monthly values and 12-month moving averages, and the Fourier transform of the complete set of 94,248 hourly mean ozone volume fractions are discussed. The data show no increase, or possibly a slight decrease, of the ozone volume fraction toward the end of the decade.
Keywords: long term ozone data, fourier analysis, ozone trend analysis, Puntijarka field station
Published in RUNG: 12.04.2021; Views: 2223; Downloads: 0
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86. Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with aerosol mass spectrometry : results from the CENICA SupersiteDara Salcedo, T. B. Onasch, Katja Džepina, M. R. Canagaratna, Qi Zhang, J. A. Huffman, P. F. DeCarlo, J. Jayne, P. Mortimer, D. Worsnop, 2006, original scientific article Abstract: An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed at the CENICA Supersite, during the Mexico City Metropolitan Area field study (MCMA-2003) from 31 March-4 May 2003 to investigate particle concentrations, sources, and processes. The AMS provides real time information on mass concentration and composition of the non-refractory species in particulate matter less than 1 mu m (NR-PM1) with high time and size-resolution. In order to account for the refractory material in the aerosol, we also present estimates of Black Carbon (BC) using an aethalometer and an estimate of the aerosol soil component obtained from Proton-Induced X-ray Emission Spectrometry (PIXE) analysis of impactor substrates. Comparisons of AMS + BC + soil mass concentration with other collocated particle instruments (a LASAIR Optical Particle Counter, a PM2.5 Tapered Element Oscillating Microbalance (TEOM), and a PM2.5 DustTrak Aerosol Monitor) show that the AMS + BC + soil mass concentration is consistent with the total PM2.5 mass concentration during MCMA-2003 within the combined uncertainties. In Mexico City, the organic fraction of the estimated PM2.5 at CENICA represents, on average, 54.6% (standard deviation sigma=10%) of the mass, with the rest consisting of inorganic compounds ( mainly ammonium nitrate and sulfate/ammonium salts), BC, and soil. Inorganic compounds represent 27.5% of PM2.5 (sigma=10%); BC mass concentration is about 11% (sigma=4%); while soil represents about 6.9% (sigma=4%). Size distributions are presented for the AMS species; they show an accumulation mode that contains mainly oxygenated organic and secondary inorganic compounds. The organic size distributions also contain a small organic particle mode that is likely indicative of fresh traffic emissions; small particle modes exist for the inorganic species as well. Evidence suggests that the organic and inorganic species are not always internally mixed, especially in the small modes. The aerosol seems to be neutralized most of the time; however, there were some periods when there was not enough ammonium to completely neutralize the nitrate, chloride and sulfate present. The diurnal cycle and size distributions of nitrate suggest local photochemical production. On the other hand, sulfate appears to be produced on a regional scale. There are indications of new particle formation and growth events when concentrations of SO2 were high. Although the sources of chloride are not clear, this species seems to condense as ammonium chloride early in the morning and to evaporate as the temperature increases and RH decreases. The total and speciated mass concentrations and diurnal cycles measured during MCMA-2003 are similar to measurements during a previous field campaign at a nearby location.
Keywords: aerosol mass-spectrometer, atmospheric aerosol, atmospheric chemistry, atmospheric physics
Published in RUNG: 12.04.2021; Views: 2366; Downloads: 0
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87. Sources and transformations of particle-bound polycyclic aromatic hydrocarbons in Mexico CityL. C. Marr, Katja Džepina, Jose L. Jimenez, F. Reisen, H. L. Bethel, Janet Arey, J. S. Gaffney, N. A. Marley, Luisa T. Molina, Mario J. Molina, 2006, original scientific article Abstract: Understanding sources, concentrations, and transformations of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere is important because of their potent mutagenicity and carcinogenicity. The measurement of particle-bound PAHs by three different methods during the Mexico City Metropolitan Area field campaign in April 2003 presents a unique opportunity for characterization of these compounds and intercomparison of the methods. The three methods are ( 1) collection and analysis of bulk samples for time-integrated gas- and particle-phase speciation by gas chromatography/ mass spectrometry; ( 2) aerosol photoionization for fast detection of PAHs on particles' surfaces; and ( 3) aerosol mass spectrometry for fast analysis of size and chemical composition. This research represents the first time aerosol mass spectrometry has been used to measure ambient PAH concentrations and the first time that fast, real-time methods have been used to quantify PAHs alongside traditional filter-based measurements in an extended field campaign. Speciated PAH measurements suggest that motor vehicles and garbage and wood burning are important sources in Mexico City. The diurnal concentration patterns captured by aerosol photoionization and aerosol mass spectrometry are generally consistent. Ambient concentrations of particle-phase PAHs typically peak at similar to 110 ng m(-3) during the morning rush hour and rapidly decay due to changes in source activity patterns and dilution as the boundary layer rises, although surface-bound PAH concentrations decay faster. The more rapid decrease in surface versus bulk PAH concentrations during the late morning suggests that freshly emitted combustion-related particles are quickly coated by secondary aerosol material in Mexico City's atmosphere and may also be transformed by heterogeneous reactions.
Keywords: aerosol mass-spectrometer, aerodynamic diameter measurements, oxygenated organic aerosols, relative rate constants
Published in RUNG: 12.04.2021; Views: 2400; Downloads: 0
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88. Secondary organic aerosol formation from anthropogenic air pollution : rapid and higher than expectedRainer Volkamer, Jose L. Jimenez, F. M. San Martini, Katja Džepina, Q. Zhang, Dara Salcedo, Luisa T. Molina, D. Worsnop, 2006, original scientific article Abstract: The atmospheric chemistry of volatile organic compounds (VOCs) in urban areas results in the formation of 'photochemical smog', including secondary organic aerosol (SOA). State-of-the-art SOA models parameterize the results of simulation chamber experiments that bracket the conditions found in the polluted urban atmosphere. Here we show that in the real urban atmosphere reactive anthropogenic VOCs (AVOCs) produce much larger amounts of SOA than these models predict, even shortly after sunrise. Contrary to current belief, a significant fraction of the excess SOA is formed from first-generation AVOC oxidation products. Global models deem AVOCs a very minor contributor to SOA compared to biogenic VOCs (BVOCs). If our results are extrapolated to other urban areas, AVOCs could be responsible for additional 3 - 25 Tg yr(-1) SOA production globally, and cause up to - 0.1 W m(-2) additional top-of-the-atmosphere radiative cooling.
Keywords: atmospheric aerosol, atmospheric chemistry, volatile organic compounds, secondary organic aerosols
Published in RUNG: 12.04.2021; Views: 3379; Downloads: 0
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89. Implementation of a Markov Chain Monte Carlo method to inorganic aerosol modeling of observations from the MCMA-2003 campaign : part IIF. M. San Martini, E. J. Dunlea, R. M. Volkamer, T. B. Onasch, J. Jayne, M. R. Canagaratna, D. Worsnop, C. E. Kolb, J. H. Shorter, Katja Džepina, 2006, original scientific article Abstract: A Markov Chain Monte Carlo model for integrating the observations of inorganic species with a thermodynamic equilibrium model was presented in Part I of this series. Using observations taken at three ground sites, i. e. a residential, industrial and rural site, during the MCMA-2003 campaign in Mexico City, the model is used to analyze the inorganic particle and ammonia data and to predict gas phase concentrations of nitric and hydrochloric acid. In general, the model is able to accurately predict the observed inorganic particle concentrations at all three sites. The agreement between the predicted and observed gas phase ammonia concentration is excellent. The NOz concentration calculated from the NOy, NO and NO2 observations is of limited use in constraining the gas phase nitric acid concentration given the large uncertainties in this measure of nitric acid and additional reactive nitrogen species. Focusing on the acidic period of 9-11 April identified by Salcedo et al. ( 2006), the model accurately predicts the particle phase observations during this period with the exception of the nitrate predictions after 10: 00 a. m. ( Central Daylight Time, CDT) on 9 April, where the model underpredicts the observations by, on average, 20%. This period had a low planetary boundary layer, very high particle concentrations, and higher than expected nitrogen dioxide concentrations. For periods when the particle chloride observations are consistently above the detection limit, the model is able to both accurately predict the particle chloride mass concentrations and provide well-constrained HCl ( g) concentrations. The availability of gas-phase ammonia observations helps constrain the predicted HCl ( g) concentrations. When the particles are aqueous, the most likely concentrations of HCl ( g) are in the sub-ppbv range. The most likely predicted concentration of HCl ( g) was found to reach concentrations of order 10 ppbv if the particles are dry. Finally, the atmospheric relevance of HCl ( g) is discussed in terms of its indicator properties for the possible influence of chlorine-mediated photochemistry in Mexico City.
Keywords: secondary organic aerosols, Mexico City, MCMA-2003 field campaign, thermodynamic equilibrium
Published in RUNG: 11.04.2021; Views: 2329; Downloads: 0
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90. Technical note : use of a beam width probe in an aerosol mass spectrometer to monitor particle collection efficiency in the fieldDara Salcedo, T. B. Onasch, M. R. Canagaratna, Katja Džepina, J. A. Huffman, J. Jayne, D. Worsnop, C. E. Kolb, S. Weimer, F. Drewnick, 2007, original scientific article Abstract: Two Aerodyne Aerosol Mass Spectrometers (Q-AMS) were deployed in Mexico City, during the Mexico City Metropolitan Area field study (MCMA-2003) from 29 March - 4 May 2003 to investigate particle concentrations, sources, and processes. We report the use of a particle beam width probe (BWP) in the field to quantify potential losses of particles due to beam broadening inside the AMS caused by particle shape (nonsphericity) and particle size. Data from this probe show that no significant mass of particles was lost due to excessive beam broadening; i.e. the shape- and size-related collection efficiency (E-s) of the AMS during this campaign was approximately one. Comparison of the BWP data from MCMA-2003 with other campaigns shows that the same conclusion holds for several other urban, rural and remotes sites. This means that the aerodynamic lens in the AMS is capable of efficiently focusing ambient particles into a well defined beam and onto the AMS vaporizer for particles sampled in a wide variety of environments. All the species measured by the AMS during MCMA-2003 have similar attenuation profiles which suggests that the particles that dominate the mass concentration were internally mixed most of the time. Only for the smaller particles ( especially below 300 nm), organic and inorganic species show different attenuation versus particle size which is likely due to partial external mixing of these components. Changes observed in the focusing of the particle beam in time can be attributed, in part, to changes in particle shape (i.e. due to relative humidity) and size of the particles sampled. However, the relationships between composition, atmospheric conditions, and particle shape and size appear to be very complex and are not yet completely understood.
Keywords: atmospheric aerosol, organic aerosols, aerodynamic lenses, Mexico City
Published in RUNG: 11.04.2021; Views: 2873; Downloads: 0
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