delta C-13 signatures of organic aerosols:Measurement method evaluation and application in a source study

Analysis of the stable carbon isotope 13C in organic carbon (OC) can give insight into sources and atmospheric processing of carbonaceous aerosols, provided the 13C source signatures are known. However, only few data on 13C signatures of OC emitted by common sources of carbonaceous aerosol are available in Europe. We present and evaluate an improved version of a measurement method to obtain δ13C signatures on organic aerosols desorbed from filter samples at three different desorption temperatures (200 °C, 350 °C and 650 °C) and apply it in a source study. With our calibration approach, the reproducibility of a L-Valine reference material desorbed at a single temperature step of 650 °C shows a standard deviation of 0.19‰ over a period of more than one year. The average δ13C value for this reference material over 248 measurements is −24.10‰, which shows only a slight bias to the nominal value of −24.03‰. Repeated analysis of ambient filter samples desorbed at three temperature steps show typical standard deviations of about 0.3‰ for all temperature steps (200 °C, 350 °C and 650 °C). Isotopic fractionation due to partial thermal desorption during the individual temperature steps was tested on single compound reference materials. It showed significant isotopic fractionation only at temperature steps, in which a very minor fraction of the compound was desorbed. Possible isotope effects caused by charring of organic material were investigated and found to be not significant. The thermal desorption method was applied to various source filter samples from the region of Naples, Italy. We analyzed two different biomass burning sources, exhaust from a city bus and traffic emissions collected in a tunnel and compared these to ambient filter samples from the same region. δ13C signatures of the total OC show values in a narrow range of about −28‰ to −26‰ for all sources, which does not allow a source apportionment only based on 13C. Nevertheless, the results add information to a source inventory of δ13C, where information of 13C in organic aerosol from specific emission sources are rare. City bus emissions show little variation of δ13C over the temperature steps, whereas biomass burning aerosol is enriched in 13C for OC desorbed at 650 °C. For PM10 samples in the urban tunnel an enrichment in δ13C at the 650 °C temperature steps was observed, which is likely caused by the contribution of carbonate carbon to the carbonaceous material desorbed at this temperature step

Calculational scheme of continuous analogue of the Newton method for reduced Hamiltonian eigenfunctions

Nuo 2003 m. ISSN 1648-8504Fizikos institutasTaikomosios informatikos katedraVytauto Didžiojo universiteta

Translationally invariant mean square radii of light atomic nuclei for higher excitations

Nuo 2003 m. ISSN 1648-8504Fizikos institutasTaikomosios informatikos katedraVytauto Didžiojo universiteta

Vidutiniai kvadratiniai 0p sluoksnio branduolių spinduliai minimaliame artėjime

Nuo 2003 m. ISSN 1648-8504Fizikos institutasTaikomosios informatikos katedraVytauto Didžiojo universiteta

Lengvųjų branduolių magnetinių momentų skaičiavimas redukuoto Hamiltoniano metodu

Nuo 2003 m. ISSN 1648-8504Fizikos institutasTaikomosios informatikos katedraVytauto Didžiojo universiteta

Seasonal Variation in Stable Isotope Ratios of Cow Milk in Vilnius Region, Lithuania

Various studies have shown that stable isotope analysis has the potential to verify the geographic origin of foods and drinks. However, stable isotope composition is not always constant in the environment and can even change in the same area. Dairy products are of particular interest as a group of foods that play an important role in feeding the population. The composition of milk is fundamentally dependent on the feeding of the cows, and thereby on a particular environment. To better understand the amount of variation in δ18O, δ13C, and δ15N values in the milk from the same area, we measured stable isotope ratios in cow milk water, artesian water, and precipitation (δ18O) as well as in bulk milk samples (δ13C and δ15N) collected in 2014⁻2016. Different water and food sources were available during the winter (artesian water only and dry grass) and summer (artesian water and fresh grass), and spring and autumn seasons reflected transitional periods. Oxygen stable isotope ratios in milk water were relatively lower in winter and transitional seasons and higher in summer, showing the dependence on the main water source. δ13C values reflected particular food sources. This study shows the applicability of the stable isotope ratio method in linking cow milk to specific environments and reveals the amount of variation in stable isotope ratios in the same area. These results could be valuable for other studies on geographical origin determination of dairy products

Isotopic niche of syntopic granivores in commercial orchards and meadows

In agricultural habitats, diets and trophic positions of syntopic granivorous small mammals are not known sufficiently. Agroecosystems may be quite complex isotopically and the most complex situation concerns the nitrogen-15 isotope as δ15N values are influenced by many internal and external fluxes. We analysed the isotopic niches of striped field (Apodemus agrarius), yellow-necked (Apodemus flavicollis), and harvest (Micromys minutus) mice living sympatrically and syntopically in apple and plum orchards, raspberry and currant plantations, and nearby meadows that were used as control habitats. Carbon (δ13C) and nitrogen (δ15N) stable isotope ratios from hair samples were used as a proxy for their diet. As the main hypothesis, we expected differences in the isotopic niches of these three species, minimising interspecific competition. All species were fully separated according to δ15N values, presuming different amounts of food of animal origin in their diet. The separation of species according to δ13C was not expressed in all habitats. The core dietary niches of these species were fully separated in the apple orchards and raspberry plantations. Intraspecific differences of the isotopic niche were not present in any of the three species: that is, resources were equally used by males and females, adults, subadults, and juveniles

Modelling the influence of nuclear fuel microstructure on fission product release

Šiame darbe siūloma atsižvelgti į branduolinio kuro (BK) tablečių polikristalinę mikrostruktūrą, moduliuojant UO2 matricos difuzijos koeficiento išraišką harmonine funkcija su periodu, artimu BK granulės dydžiui. Skaitmeninis lygties sprendimas rodo, kad dalijimosi produktai (DP) iš BK matricos smelkiasi lėčiau lyginant su atveju, kai į kuro mikrostruktūrą neatsižvelgiame. Siejame tai su DP pagavimu BK tarpgranulinėse ertmėse. Nustatytas DP koncentracijos radialinis pasiskirstymas BK tabletėje yra kokybiškai panašus į pateikiamus literatūrojeThe gaseous fission product release model including modulation of the diffusion coefficient by harmonic function with a period matching the fuel grain size has been considered. Numerical solution of diffusion equation shows reduced diffusion rate. It is related to the trapping of fission products in inter-granular bubbles of the fuel. The calculated profile of fission product concentration distribution is similar to the one obtained in the experimental studiesFizikos institutasVytauto Didžiojo universiteta