The chemical and isotopic composition of organic aerosol (OA) samples collected on PM1 filters was determined as a function of desorption temperature to investigate the main sources of organic carbon ...and the effects of photochemical processing on atmospheric aerosol. The filter samples were collected at an urban (54°38′ N, 25°18′ E), coastal (55°55′ N, 21°00′ E) and forest (55°27′ N, 26°00’ E) site in Lithuania in March 2013. They can be interpreted as winter-time samples because the monthly averaged temperature was −4 °C.
The detailed chemical composition of organic compounds was analysed with a thermal desorption PTR-MS. The mass concentration of organic aerosol at the forest site was roughly by a factor of 30 lower than at the urban and coastal site. This fact could be an indication that in this cold month the biogenic secondary organic aerosol (SOA) formation was very low. Moreover, the organic aerosol collected at the forest site was more refractory and contained a larger fraction of heavy molecules with m/z > 200.
The isotopic composition of the aerosol was used to differentiate the two main sources of organic aerosol in winter, i.e. biomass burning (BB) and fossil fuel (FF) combustion. Organic aerosol from biomass burning is enriched in 13C compared to OA from fossil fuel emissions. δ13COC values of the OA samples showed a positive correlation with the mass fraction of several individual organic compounds. Most of these organic compounds contained nitrogen indicating that organic nitrogen compounds formed during the combustion of biomass may be indicative of BB. Other compounds that showed negative correlations with δ13COC were possibly indicative of FF. These compounds included heavy hydrocarbons and were on the average less oxidized than the bulk organic carbon.
The correlation of δ13COC and the O/C ratio was positive at low but negative at high desorption temperatures at the forest site. We propose that this might be due to photochemical processing of OA. This processing can lead to accumulation of carbon in the more refractory organic fraction that is depleted in 13C compared with the less refractory organic fraction. Detailed laboratory experiments are necessary to further investigate the aging of aerosol particles before firm conclusions can be drawn.
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•Photochemical processing of organic aerosol at the forest site.•δ13C of organic aerosol provided insight into sources.
We measured stable carbon isotope ratios of total carbon (TC) and organic carbon (OC) in fine carbonaceous aerosol fraction sampled in August and September 2013 at urban, coastal and forest sites in ...Lithuania. δ13C values of TC for all three sites over the whole measurement period varied from −29.3 to −26.6‰, which is in the range of particles emitted by fossil fuel combustion in Eastern Europe. The isotopic composition at the forest and coastal site showed a similar variation during two contrasting pollution periods. δ13C values in the clean period were more variable, whereas the polluted period was characterized by a gradual enrichment in δ13C compared to the clean period. In the polluted period air masses originated from southern, southeastern or southwestern direction, indicating long-range transport of pollutants from Eastern Europe and Southern Europe to Lithuania. Oxidative processing during long-range transport or the different source signatures (e.g., enriched 13C signature of gasoline used in Western Europe vs. Eastern Europe) could cause the less negative δ13COC values during the polluted episode. δ13C for OC desorbed from the filter samples was separately measured during three different temperature steps (200 °C, 350 °C and 650 °C). OC desorbed at 200 °C had the most depleted 13C signature of around −29‰ at all three sites.
A comparison with previously published data measured during the winter at the same sites showed that both TC and OC had less negative δ13C values in winter than in summer, which can be explained by the contribution of biomass/coal burning sources in winter. At the urban site δ13C of OC did not change much with increasing desorption temperature in winter, which is typical for primary sources, but in the summer δ13C of OC was depleted for lower desorption temperatures, possibly due to the influence of SOA formation. A higher fraction of more refractory OC in summer compared to winter-time suggests active photochemical processing of the primary organic aerosol as an important process at all three sites.
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•13C signature of organic aerosol reveals main sources.•Isotopic composition shows seasonal difference.•δ13COC change via kinetic fractionation.
Carbonaceous aerosols exhibit seasonal variations due to a complex interplay of emission sources, meteorological conditions, and chemical processes. This study presents the first year-round ...dual‑carbon isotopic analysis of carbonaceous aerosols in Northeastern Europe (Lithuania). The emphasis was placed on the processes affecting carbonaceous submicron particle (PM1) concentrations and their isotopic composition (δ13CTC, fc) during different seasons. Aerosol particles were collected in the two distinct sites: at an urban background site (Vilnius) and a coastal site (Preila). The concentrations of total carbon (TC) and black carbon (BC) varied both spatially and temporally. The annual average concentrations were 4 μg/m3 for TC and 2.3 μg/m3 for BC at the urban background site. They were considerably lower at the coastal site with 2.9 μg/m3 for TC and 0.74 μg/m3 for BC. The peak concentrations of TC and BC that occur during the cold season indicate a significant impact from residential heating. The δ13C in aerosols exhibited a distinct seasonal cycle with depleted δ13CTC values during the warm season (April–October). Through the integration of isotopic composition, contemporary carbon (fc), and BC source apportionment, we achieved precise predictions of isotopic parameter changes, encompassing pollution sources and the influence of meteorological parameters. To better understand the respective contributions of local and regional sources, air mass trajectories, wind patterns (speed and direction), and the polar conditional probability function (CPF) were studied in parallel. The study indicates that the isotopic composition of PM1 at both sites is primarily controlled by emission sources (local and regional), while meteorological conditions (temperature and mixing layer height) have less influence. These variations have important implications for regional air quality, climate dynamics, and public health, which are persistently subject to continuous research and monitoring.
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•Seasonal variations in dual carbon isotopic composition were observed at urban background and coastal sites.•Total carbon (TC) and black carbon (BC) concentrations showed seasonal fluctuations, peaking during the cold season.•Different seasonal δ13C values point to different seasonal TC sources.
Size-segregated aerosol particles were collected during winter sampling campaigns at a coastal (55°37′ N, 21°03′E) and an urban (54°64′ N, 25°18′ E) site. Organic compounds were thermally desorbed ...from the samples at different temperature steps ranging from 100 °C to 350 °C. The organic matter (OM) desorbed at each temperature step is analysed for stable carbon isotopes using an isotope ratio mass spectrometer (IRMS) and for individual organic compounds using a Proton Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-MS). The OM desorbed at temperatures <200 °C was classified as less refractory carbon and the OM desorbed at temperatures between 200 °C and 350 °C was classified as more refractory carbon. At the coastal site, we identified two distinct time periods. The first period was more frequently influenced by marine air masses than the second time period, which was characterized by Easterly wind directions and continental air masses. During the first period OM contained a large fraction of hydrocarbons and had a carbon isotopic signature typical of liquid fossil fuels in the region. Organic mass spectra provide strong evidence that shipping emissions are a significant source of OM at this coastal site. The isotopic and chemical composition of OM during the second period at the coastal site was similar to the composition at the urban site. There was a clear distinction in source contribution between the less refractory OM and the more refractory OM at these sites. According to the source apportionment method used in this study, we were able to identify fossil fuel burning as predominant source of the less refractory OM in the smallest particles (D50 < 0.18 μm), and biomass burning as predominant source of the more refractory OM in the larger size range (0.32 < D50 < 1 μm).
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•Biomass burning is the predominant source of the more refractory carbonaceous aerosol at particle sizes >340 nm.•Fossil fuel burning was identified as predominant source of the less refractory fraction for <180 nm particles.•Heavy fuel exhaust emissions from ships can enhance OC concentrations at the coastal site.
Chemical and isotopic analysis of carbonaceous aerosol particles revealed a clear distinction in source contribution at coastal and urban sites.
Polyethylene 2.6-naphthalate (PEN) is a promising plastic scintillator material. In this paper, a thin PEN film was used for detection, identification, and energy spectrum measurements of various ...ionizing radiation particles. A thin PEN film was used to separate α (5.49 MeV) and β (up to 2.2 MeV) particles coming from 238Pu and 90Sr + 90Y sources, respectively, as well as for the neutron (up to 14 MeV) and gamma separation from the isotopic PuBe neutron source. Acquired photomultiplier pulses were analyzed by the long tail method based on the delayed fluorescence intensity dependence on the mass and charge of particles absorbed. For determination of the separation quality, the figure of merit (FOM), based on the ratio of short and long tails, was used. It was found that depending on the FOM values of neutron/gamma and α/β separation, the thin PEN film is suitable for the ionizing radiation particle separation.
Part I (Remeikis et al., 2021) of the review analyzed research done on the modeling of the RBMK-1500 reactor and its practical applications during operation of Ignalina Nuclear Power Plant. In this ...second review article the survey of the research done on modeling for decommissioning of the RBMK-1500 reactor as well as some perspectives for the future investigations are presented. During the last few decades considerable modeling experience has been accumulated in the field of radioactive waste management for RBMK-1500 decommissioning: inventory calculations of nuclear fuel and activated reactor construction materials as well as characterization of operational and decommissioning waste applying the modeling supported scaling factor method, evaluation of spent nuclear fuel containers for dry storage, fuel pools and fuel transportation safety, radioactive waste behavior under geological disposal conditions and alternative vision of nuclear waste transmutation. Important findings and key methodologies are highlighted and the need of scientific input is discussed. Additionally, an outlook on further research concerning RBMK-1500 reactor studies is provided.
This review article presents the research done on the modeling of the RBMK-1500 reactor and its practical applications during reactor’s operation. Studies of the modeling for reactor safety ...improvement and research on Ignalina NPP during the normal and accidental conditions are reviewed: reactor neutronics, depletion of nuclear fuel, thermal-hydraulics, nuclear fuel thermo-mechanical behavior, fission product release and contamination of reactor circuit, nuclear fuel composition for design and increased enrichment with burnable poison, burn-up credit and benchmark calculations. Important findings and key modeling techniques are highlighted and the need of scientific input is discussed. The survey of the research done on modeling for decommissioning of the RBMK-1500 reactor is presented in the part II of the review Remeikis et al. (to be published).
Dual carbon isotope analysis of marine aerosol samples has been performed for the first time demonstrating a potential in organic matter apportionment between three principal sources: marine, ...terrestrial (non-fossil) and fossil fuel due to unique isotopic signatures. The results presented here, utilising combinations of dual carbon isotope analysis, provides conclusive evidence of a dominant biogenic organic fraction to organic aerosol over biologically active oceans. In particular, the NE Atlantic, which is also subjected to notable anthropogenic influences via pollution transport processes, was found to contain 80 % organic aerosol matter of biogenic origin directly linked to plankton emissions. The remaining carbonaceous aerosol was of terrestrial origin. By contrast, for polluted air advected out from Europe into the NE Atlantic, the source apportionment is 30 % marine biogenic, 40 % fossil fuel, and 30 % continental non-fossil fuel. The dominant marine organic aerosol source in the atmosphere has significant implications for climate change feedback processes.
Six different biomass fuel types (wood pellets, sunflower stalk pellets, straw pellets, buckwheat shells, mixed biomass waste pellets, and grain screenings) and wastewater sludge pellets were burned ...under controlled conditions to determine the effect of the biomass type on the emitted particulate matter mass and stable carbon isotope composition of bulk and size-segregated particles. Aerosol particles were sampled using the total suspended particle (TSP) sampler and a micro-orifice uniform deposit impactor (MOUDI). The results demonstrated that particle emissions were dominated by the submicron particles (size <1µm) in all biomass types. However, significant differences in emissions of submicron particles and their dominant sizes were found between different biomass fuels. The isotopic fractionation between aerosol particles and original biomass material varied from −0.94±0.23‰ to 1.12±0.16‰. The largest negative fractionation −0.94±0.23‰ was obtained for the wood pellet fuel type while the largest positive isotopic fractionation (1.12±0.16‰) was observed during the grain screenings combustion. The carbon isotope composition of MOUDI samples compared very well with the isotope composition of TSP samples indicating consistency of the results. The measurements of the stable carbon isotope ratio in size-segregated aerosol particles suggested that combustion processes could strongly affect isotopic fractionation in aerosol particles of different sizes thereby potentially affecting an interpretation of ambient atmospheric observations.
•Different biomass fuel types were investigated during controlled burning conditions.•Stable carbon isotopes were analyzed in size-segregated aerosol particles and TSP.•Stable carbon isotope fractionation (Δ13C) between aerosol particles and fuel depended on combustion conditions.•For the various biomass fuel types Δ13C was different in separate aerosol particle sizes.
•Simple re-arrangement of the GaN-based LEDs into radiation sensors.•Simultaneous recording of the electrical and optical response signals.•Techniques for monitoring of the evolution of sensor ...characteristics during irradiation.•Radiation-hard GaN-LED-based sensors and dosimeters possible for space applications.•Heavily irradiated GaN-LEDs are functional for remote transmission of dosimetry data.
We report on variations of the electrical and optical characteristics of commercial GaN blue LEDs, acting as radiation sensors or dosimeters, during 1.6MeV proton irradiation. Transients of the barrier and storage capacitance have been examined simultaneously with proton-excited luminescence. The pulsed capacitance technique was shown to be a useful tool for the control of changes of the effective density of dopants in the LED structure during proton irradiation, due to introduced radiation defects. The minority carrier injection efficiency can be estimated by measuring the charging current transients of the barrier and storage capacitance. The transient current measurements imply rather fast response of the GaN LED hadron radiation sensors. Also, our results show that the intensity and spectral variations of the proton-excited blue luminescence of the LEDs can be used for the estimation of hadron flux and fluence, respectively. This implies that GaN LED-based sensors can be used for the synchronous detection of hadron irradiation by recording the optical and electrical signals.
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