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Vertical profiling of fresh biomass burning aerosol optical properties over the Greek urban city of Ioannina, during the PANACEA winter campaign
Christina-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: 122; Prenosov: 3
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Performance analysis of high-spectral-resolution lidar with/without laser seeding technique for measuring aerosol optical properties
Fengjia Gao, Fei Gao, Gaipan Li, Fan Yang, Li Wang, Song Yuehui, Dengxin Hua, Samo Stanič, 2024, izvirni znanstveni članek

Opis: High-spectral-resolution lidar (HSRL) is a powerful tool for aerosol measurements. With/without laser seeding technique in the transmitted laser, the HSRL can be distinguished as the single-longitudinal-mode (SLM) HSRL or the multi-longitudinal-mode (MLM) HSRL, and the Mach-Zehnder interferometer (MZI) with periodic transmittance function can be used as the spectral discriminator in both the SLM HSRL and MLM HSRL. To in-depth knowledge of the respective advantages of the SLM HSRL and MLM HSRL for measuring aerosol optical properties, the working principle, optimal parameter setting, and detection performance of the SLM HSRL and MLM HSRL are analyzed and discussed in detail, respectively. The working principle of the SLM HSRL and MLM HSRL indicate that the effective transmittance of MZI is the important parameter of data retrieval, the main source of retrieval uncertainties, and the key factor of MZI optical path difference (OPD) settings. To ensure that the MZI can achieve the preferable separation for aerosol Mie scattering signals and molecular Rayleigh scattering signals, the optimal OPDs of MZI are set at 165 mm and 1000 mm in the SLM HSRL and MLM HSRL from the aspects of the effective transmittance of MZI and the spectral discrimination ratio (SDR). Besides, to analyze the influence of frequency difference and divergence angle for the detection performance of HSRL, the effective transmittance of MZI and SDR are simulated and the results show that the MLM HSRL has higher requirements for the environmental parameters and the echo beam collimation than the SLM HSRL. Moreover, the HSRLs with SLM and MLM transmitted lasers are constructed in Xi'an for measuring aerosol optical properties. The preliminary measurement results show that the range square corrected signal (RSCS) of Rayleigh channel is smaller than that of Mie channel in both the SLM HSRL and MLM HSRL, while the difference between RSCS of Rayleigh channel and RSCS of Mie channel in the SLM HSRL is larger than that in the MLM HSRL, and the detection range of the SLM HSRL is lower than that of the MLM HSRL.
Ključne besede: aerosol optical properties, high-spectral-resolution lidar, single-longitudinal-mode, multi-longitudinal-mode, spectral discrimination ratio
Objavljeno v RUNG: 28.02.2024; Ogledov: 463; Prenosov: 2
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No-hole λ-L (k, k – 1, …, 2,1)-labeling for square grid
Soumen Atta, Stanisław Goldstein, Priya Ranjan Sinha Mahapatra, 2017, izvirni znanstveni članek

Opis: Motivated by a frequency assignment problem, we demonstrate, for a fixed positive integer k, how to label an infinite square grid with a possibly small number of integer labels, ranging from 0 to λ −1, in such a way that labels of adjacent vertices differ by at least k, vertices connected by a path of length two receive values which differ by at least k − 1, and so on. The vertices which are at least k + 1 distance apart may receive the same label. By finding a lower bound for λ, we prove that the solution is close to optimal, with approximation ratio at most 9/8. The labeling presented is a no-hole one, i.e., it uses each of the allowed labels at least once.
Ključne besede: graph labeling, labeling number, no-hole labeling, square grid, frequency assignment problem, approximation ratio
Objavljeno v RUNG: 17.04.2023; Ogledov: 817; Prenosov: 0
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Secondary organic aerosol formation from semi- and intermediate-volatility organic compounds and glyoxal : relevance of O/C as a tracer for aqueous multiphase chemistry
Eleanor M. Waxman, Katja Džepina, Barbara Ervens, Julia Lee-Taylor, Bernard Aumont, Jose L. Jimenez, Sasha Madronich, Rainer Volkamer, 2013, izvirni znanstveni članek

Opis: The role of aqueous multiphase chemistry in the formation of secondary organic aerosol (SOA) remains difficult to quantify. We investigate it here by testing the rapid formation of moderate oxygen-to-carbon (O/C) SOA during a case study in Mexico City. A novel laboratory-based glyoxal-SOA mechanism is applied to the field data, and explains why less gas-phase glyoxal mass is observed than predicted. Furthermore, we compare an explicit gas-phase chemical mechanism for SOA formation from semi- and intermediate-volatility organic compounds (S/IVOCs) with empirical parameterizations of S/IVOC aging. The mechanism representing our current understanding of chemical kinetics of S/IVOC oxidation combined with traditional SOA sources and mixing of background SOA underestimates the observed O/C by a factor of two at noon. Inclusion of glyoxal-SOA with O/C of 1.5 brings O/C predictions within measurement uncertainty, suggesting that field observations can be reconciled on reasonable time scales using laboratory-based empirical relationships for aqueous chemistry.
Ključne besede: secondary organic aerosol, glyoxal, aqueous multiphase chemistry, oxygen-to-carbon ratio, single scattering albedo
Objavljeno v RUNG: 11.04.2021; Ogledov: 2179; Prenosov: 0
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Carcinogenic organic content of particulate matter at urban locations with different pollution sources
Gordana Pehnec, Ivana Jakovljević, Ranka Godec, Zdravka Sever Štrukil, Sabina Žero, Jasna Huremović, Katja Džepina, 2020, izvirni znanstveni članek

Opis: Polycyclic aromatic hydrocarbons (PAHs) are compounds known for their adverse effects on human health. Many of them are proven carcinogens, especially those with 5 and 6 aromatic rings, which under normal tropospheric conditions are found in the particle-phase. Benzo(a)pyrene (BaP) is often measured as their general representative. Sarajevo, the capital of Bosnia and Herzegovina, is among the European cities with the poorest air quality. However, in Sarajevo PAHs are neither routinely measured within the air quality monitoring network nor have been a subject of extended, continuous field studies during the most polluted cold periods of the year. The capital of Croatia, Zagreb, is located approximately 300 km air distance north-west from Sarajevo. PAH mass concentrations in Zagreb have been measured continuously since 1994 within air quality monitoring networks. During winter 2017/2018, the SAFICA project (Sarajevo Canton Winter Field Campaign 2018) was carried out in order to characterize the chemical composition of organic and inorganic aerosol in the Sarajevo Canton. This paper presents the results of PAH measurements in the cities of Sarajevo and Zagreb at one urban location per city. Daily (24 h), continuous samples of PM10 (particulate matter with aerodynamic diameters ≤10 μm) were collected during heating season, from December 27, 2017 to February 27, 2018. Mass concentrations of eleven particle-phase PAHs in Sarajevo and Zagreb from filter samples collected during the same period were compared. The average BaP ambient mass concentrations in Sarajevo and Zagreb were 6.93 ng m−3 and 3.11 ng m−3, respectively. The contribution of BaP to the total PAH mass concentration was similar at both locations (11%). However, much higher contributions of particle-phase fluoranthene and pyrene were found in Sarajevo. Contributions of individual PAH, diagnostic ratios and factor analysis indicate that combustion of gasoline and diesel from vehicle traffic are a potential source of PAHs at both locations, as well as combustion of other liquid fossil fuels (petroleum and fuel oil). Wood burning was occasionally indicated as a PAH emission source in Zagreb, while in Sarajevo the contribution of PAHs from wood and coal combustion was more evident. Calculated value for total carcinogenic potency (TCP) of PAHs, which was estimated using toxic equivalence factors from the literature, in PM10 samples collected in Sarajevo was more than twice higher than in Zagreb (10.6 ng m−3 and 4.7 ng m−3, respectively). BaP had the highest contribution to the TCP at both locations (69 and 67%).
Ključne besede: carcinogenic potency, diagnostic ratio, factor analysis, PM10, polycyclic aromatic hydrocarbons
Objavljeno v RUNG: 09.04.2021; Ogledov: 2233; Prenosov: 0
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Stable carbon isotope analysis of selected halocarbons at parts per trillion concentration in an urban location
M Iqbal Mead, M Anwar H Khan, Ian D Bull, Iain R. White, Graham Nickless, Dudley E Shallcross, 2008, izvirni znanstveni članek

Opis: ∂13C values of a suite of halocarbons have been determined in an urban background site in Bristol, UK. A novel mobile preconcentration system, based on the use of multi-adsorbent sample tubes, has been developed for trapping relatively large-volume air samples in potentially remote areas. An Adsorption Desorption System-Gas Chromatography-Electron Capture Detector was used to measure the mixing ratios of the selected halocarbon species, while a Gas ChromatographyCombustionIsotope Ratio Mass Spectrometer was used to determine ∂13C values. For the species with strong local sources, the variation of isotope ratios has been observed over the experimental period. Some of the results reported in the present study differ from previously reported values and reasons for this are discussed. The reporting of different ∂13C values for selected halocarbons from different areas in the present study suggests that ∂13C values may be used to determine the relative magnitudes of anthropogenic and biogenic sources.
Ključne besede: Adsorption Desorption System (ADS), Automated Thermal Desorber (ATD), Electron Capture Detector (ECD), Gas Chromatography (GC), Isotope Ratio Mass Spectrometry (IRMS)
Objavljeno v RUNG: 18.07.2019; Ogledov: 3194; Prenosov: 0
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Biogas production from brewery spent grain as a mono-substrate in a two-stage process composed of solid-state anaerobic digestion and granular biomass reactors
Mario Panjicko, Gregor Drago Zupančič, Romana Marinšek-Logar, Lijana Fanedl, Marina Tišma, Bruno Zelić, 2017, izvirni znanstveni članek

Opis: Anaerobic digestion of brewery spent grain as a mono-substrate was studied. Brewery spent grain is a substrate consisting largely of cellulose, hemicellulose and lignin, which are difficult to degrade anaerobically, mostly due to the presence of degradation products, such as phenolic compounds, which cause process inhibition. Therefore, a two-stage system was used for anaerobic digestion. Anaerobic digestion was phase separated in a solid-state anaerobic digestion reactor, where microbiological hydrolysis and acidogenesis occurred and in a granular biomass reactor where mostly methanogenesis was performed. The overall process exhibited total solids degradation efficiency between 75.9 and 83.0 %. Average specific biogas production was 414±32 L/kg, whereas biomethane production was 224±34 L/kg of added total solids. Granular biomass after adaptation exhibited stable operation at substrate C/N ratios in range 0.16 – 4.68. p-cresol was present in concentrations up to 45 mg/L and during the process was successfully degraded by granular biomass. The excellent adaptability of granular biomass was confirmed by 68.2 % shift in bacterial and a 31.8 % shift in archaeal community structure in a granular biomass reactor. The structure of the bacterial community from granular biomass reactor and solid-state anaerobic digestion reactor remained 79.4 % similar at the end of the experiment, whereas archaeal community was only 31.6 % similar. The process exhibited stable operation for 198 days, which shows that brewery spent grain can be successfully anaerobically digested and used for biogas production.
Ključne besede: biogas production, brewery spent grain, C/N ratio, dry digestion, microbial biomass, solid-state anaerobic digestion
Objavljeno v RUNG: 18.08.2017; Ogledov: 4413; Prenosov: 0
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