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Abstract: Brown carbon (BrC) is a fraction of organic aerosol (OA) that absorbs radiation in the ultraviolet and short visible wavelengths. Its contribution to radiative forcing is uncertain due to limited knowledge of its imaginary refractive index (k). This study investigates the variability of k for OA from wildfires, residential, shipping, and traffic emission sources over Europe. The Multiscale Online Nonhydrostatic Atmosphere Chemistry (MONARCH) model simulated OA concentrations and source contributions, feeding an offline optical tool to constrain k values at 370 nm. The model was evaluated against OA mass concentrations from aerosol chemical speciation monitors (ACSMs) and filter sample measurements, as well as aerosol light absorption measurements at 370 nm derived from an Aethalometer™ from 12 sites across Europe. Results show that MONARCH captures the OA temporal variability across environments (regional, suburban, and urban background). Residential emissions are a major OA source in colder months, while secondary organic aerosol (SOA) dominates in warmer periods. Traffic is a minor primary OA contributor. Biomass and coal combustion significantly influence OA absorption, with shipping emissions also notable near harbors. Optimizing k values at 370 nm revealed significant variability in OA light absorption, influenced by emission sources and environmental conditions. Derived k values for biomass burning (0.03 to 0.13), residential (0.008 to 0.13), shipping (0.005 to 0.08), and traffic (0.005 to 0.07) sources improved model representation of OA absorption compared to a constant k. Introducing such emission source-specific constraints is an innovative approach to enhance OA absorption in atmospheric models.
Keywords: aerosols, brown carbon, source contribution analysis
Published in RUNG: 04.03.2025; Views: 547; Downloads: 6
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Keywords: DNA repairing mechanism, protein modeling, chromatin remodeler, helicase-like transcription factor
Published in RUNG: 15.11.2024; Views: 1059; Downloads: 2
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Keywords: astronomija, izbruhi sevanja gama, supernove
Published in RUNG: 07.10.2024; Views: 865; Downloads: 3
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Abstract: Vsaka filmska produkcija je sestavljena iz predprodukcije, produkcije in postprodukcije. Diplomsko delo govori o težavah v vseh fazah ustvarjalnega procesa. Vsako poglavje se začne s prikazom, kako naj bi v profesionalnem svetu filma posamezna faza produkcije potekala, nato pa opisuje mojo lastno izkušnjo in težave, na katere smo z ekipo med ustvarjanjem naleteli. Teoretični deli so povzeti iz literature in intervjuja s slovensko asistentko režije Urško Kos. Nalogo začnem z opisom predprodukcije in njenih podpoglavj, kjer bralec lahko vidi, kaj vse je treba narediti, preden sploh lahko začnemo snemati film: od ideje do scenarija, iskanja ekipe, igralcev in lokacij ter do izposoje opreme tik pred snemanjem. Z opisom osebnega doživljanja vsake faze predprodukcije prikažem, koliko stvari gre lahko narobe že pri na videz povsem preprostih zadevah. V nadaljevanju diplomska naloga govori o produkciji filma oziroma o snemanju. Vsak snemalni dan povzamem v svojem poglavju ter opišem delo na setu med snemanjem kratkega filma. V primerjavi z navedenimi profesionalnimi okoliščinami, kjer popišem vse potrebne člane ekipe za potek snemanja, je vidno pomanjkanje ekipe v pri snemanju študentskega filma. V opisu zadnje faze, postprodukcije, naloga govori o delu na filmu po tem, ko je film posnet: od prvega pregledovanja materiala do montaže, po končani montaži slike pa urejanje barv slike in montaža zvoka. Faza ustvarjanja filma, ki pretežno poteka na računalnikih, a vendarle z raznolikimi zapleti. Zaključek je namenjen predvsem bralcem, ki se bodo v prihodnosti prvič srečevali s filmsko produkcijo. Celotna naloga je napisana z mislijo na generacije za menoj, ki se bodo s težavami filmske produkcije še srečevale, in z upanjem, da jim bo morda moja izkušnja pomagala pri prvih korakih. Zato v zaključku zapišem tudi nekaj vzpodbudnih besed.
Keywords: film, filmska produkcija, težave, snemanje, predprodukcija, postprodukcija, igralci, ekipa, scenarij, montaža, diplomske naloge
Published in RUNG: 30.09.2024; Views: 958; Downloads: 11
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Abstract: Abstract. Black carbon (BC) is recognized as the most important warming agent among atmospheric aerosol particles. The absorption efficiency of pure BC is rather well-known, nevertheless the mixing of BC with other aerosol particles can enhance the BC light absorption efficiency, thus directly affecting Earth's radiative balance. The effects on climate of the BC absorption enhancement due to the mixing with these aerosols are not yet well constrained because these effects depend on the availability of material for mixing with BC, thus creating regional variations. Here we present the mass absorption cross-section (MAC) and absorption enhancement of BC particles (Eabs), at different wavelengths (from 370 to 880 nm for online measurements and at 637 nm for offline measurements) measured at two sites in the western Mediterranean, namely Barcelona (BCN; urban background) and Montseny (MSY; regional background). The Eabs values ranged between 1.24 and 1.51 at the urban station, depending on the season and wavelength used as well as on the pure BC MAC used as a reference. The largest contribution to Eabs was due to the internal mixing of BC particles with other aerosol compounds, on average between a 91 % and a 100 % at 370 and 880 nm, respectively. Additionally, 14.5 % and 4.6 % of the total enhancement at the short ultraviolet (UV) wavelength (370 nm) was due to externally mixed brown carbon (BrC) particles during the cold and the warm period, respectively. On average, at the MSY station, a higher Eabs value was observed (1.83 at 637 nm) compared to BCN (1.37 at 637 nm), which was associated with the higher fraction of organic aerosols (OA) available for BC coating at the regional station, as denoted by the higher organic carbon to elemental carbon (OC:EC) ratio observed at MSY compared to BCN. At both BCN and MSY, Eabs showed an exponential increase with the amount of non-refractory (NR) material available for coating (RNR-PM). The Eabs at 637 nm at the MSY regional station reached values up to 3 during episodes with high RNR-PM, whereas in BCN, Eabs kept values lower than 2 due to the lower relative amount of coating materials measured at BCN compared to MSY. The main sources of OA influencing Eabs throughout the year were hydrocarbon OA (HOA) and cooking-related OA (COA), i.e. primary OA (POA) from traffic and cooking emissions, respectively, at both 370 and 880 nm. At the short UV wavelength (370 nm), a strong contribution to Eabs from biomass burning OA (BBOA) and less oxidized oxygenated OA (LO-OOA) sources was observed in the colder period. Moreover, we found an increase of Eabs with the ageing state of the particles, especially during the colder period. This increase of Eabs with particle ageing was associated with a larger relative amount of secondary OA (SOA) compared to POA. The availability of a long dataset at both stations from offline measurements enabled a decade-long trend analysis of Eabs at 637 nm, that showed statistically significant (s.s.) positive trends of Eabs during the warmer months at the MSY station. This s.s. positive trend in MSY mirrored the observed increase of the OC:EC ratio over time. Moreover, in BCN during the COVID-19 lockdown period in spring 2020 we observed a sharp increase of Eabs due to the observed sharp increase of the OC:EC ratio. Our results show similar values of Eabs to those found in the literature for similar background stations.
Keywords: black carbomn, coating, organic aerosol, light absorption
Published in RUNG: 10.05.2024; Views: 1602; Downloads: 5
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