Seasonal changes of sources and volatility of carbonaceous aerosol at urban, coastal and forest sites in Eastern Europe (Lithuania)

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

Stable carbon and nitrogen isotope ratio in PM1 and size segregated aerosol particles over the Baltic Sea

We analysed delta C-13 of total carbon (TC) and PN of total nitrogen (TN) in submicron (PM1) and size segregated aerosol particles ( PM0.056-2.5) collected during a cruise in the Baltic Sea from 9 to 17 November 2012. PM1 were characterized by the highest delta C-13 (-26.4 parts per thousand) and lowest delta N-15 (-0.2 and 0.8 parts per thousand) values when air masses arrived from the southwest direction (Poland). The obtained delta C-13 values indicated that combined emissions of coal and diesel/gasoline combustion were the most likely sources of TC. The depleted delta N-15 values indicated that TN originated mainly from liquid fuel combustion (road traffic, shipping) during this period. The lowest PC and highest delta N-15 values were determined in PM1 samples during the western airflow when the air masses had no recent contact with land. The highest delta N-15 values were probably associated with chemical aging of nitrogenous species during long-range transport, the lowest delta C-13 values could be related to emissions from diesel/gasoline combustion, potentially from ship traffic. The delta C-13 analysis of size-segregated aerosol particles PM0.056-2.5 revealed that the lowest delta C-13 values were observed in the size range from 0.056 to 0.18 mu m and gradual C-13 enrichment occurred in the size range from 0.18 to 2.5 mu m due to different sources or formation mechanisms of the aerosols

Immediate increase in isotopic enrichment in small mammals following the expansion of a great cormorant colony

Colonies of great cormorants (Phalacrocorax carbo) impact terrestrial ecosystems through the transport of nutrients from aquatic to terrestrial ecosystems. Deposited guano overload the ecosystem with N and P, change soil pH and damage vegetation. The ways in which small mammals are impacted, however, are little known. We aimed to evaluate the effects of an expanding great cormorant colony, testing if the expansion immediately increased the input of biogens into the forest ecosystem and, further, if the growing influence of the colony was reflected in basal resources (plants and invertebrates) and the hair of small mammals. δ15N and δ13C signatures were analyzed in granivorous yellow-necked mice (Apodemus flavicollis), omnivorous bank voles (Myodes glareolus) and basal resources of animal and plant origin from the territory of a colony of great cormorants situated near the Baltic Sea in west Lithuania. We found that biogens transferred by great cormorants to the terrestrial ecosystem affected the potential foods of the small mammals and led to highly elevated and variable δ15N values. An increase of the size of the colony in 2015 resulted in isotopic enrichment of the small mammals in the zone of expansion in comparison to levels in 2014. The increase of δ15N in A. flavicollis was 7.5 % (p < 0.05) in the ecotone and 5.7 % in the expansion zone. The decrease in δ13C signatures in A. flavicollis was 4.5 % (p < 0.1) in the expansion zone and 3.1 % (p < 0.001) in the colony. In M. glareolus, the decrease in δ13C signatures was 8.5 % in the expansion zone, 3.3 % (p < 0.1) in the control zone and 2.6 % in the ecotone. Isotopic niches (central ellipses) of A. flavicollis in the colony and between the control and expansion zones were separated in 2014 and 2015, while they partially overlapped in the ecotone. The isotopic niches of M. glareolus in 2014 and 2015 were separated in the ecotone and had a small overlap in the colony. For most of the resources tested, the isotopic signatures in the established colony area were significantly higher than in the rest of cormorant-inhabited area. In the colony, the δ15N values in plants (16.9 ± 1.1 ‰) were higher than in invertebrates (13.6 ± 0.4 ‰). In the ecotone, the δ15N values were 12.0 ± 1.4 in plants and 14.7 ± 0.04 ‰ in invertebrates, while in the expansion zone they were 7.2 ± 3.0 and 9.9 ± 3.8 ‰, respectively. δ15N-rich resources led to increased δ15N values in the hair of A. flavicollis and M. glareolus. Thus, biogens from the great cormorant colony immediately affected small mammals through their food sources

Genetic algorithm in radioactive decay rate variations analysis

Measurements of the relative changes $\Delta\lambda/\lambda$ of the electron capture rate is a direct experimental way to determine the changes $\Delta\rho(0)$ of electron density on the nucleus $\rho(0)$, which are necessary for the determination of the Mössbauer isomer shift calibration constants. In this paper we present our results obtained using various chemical compounds with {}^{125}{\ab I} isotope. Fitting the results to the theoretical model, we find the parameters, and using a genetic algorithm we solve the so-called "ill-posed"problem. The calculated $\Delta\lambda/\lambda$ values compared with \ab{KIO_3} are ($-2.9 \pm 0.3)\cdot 10^{-4}$ for \ab{Na_3H_2IO_6}, ($-1.6 \pm 0.1)\cdot 10^{-4}$ for \ab{KIO_4}, ($-1.4 \pm 0.6)\cdot 10^{-4}$ for CsI

Exposure of biota in the cooling pond of Ignalina NPP: hydrophytes

The radiological assessment of non-human biota is now accepted by a number of international bodies. In this connection the scientific basis to assess and evaluate biota internal and external radiation exposure is required. This paper presents the comparison of freshwater biota (hydrophyte species) exposure due to discharged anthropogenic radionuclides with that due to natural background radiation. The radionuclides from Ignalina Nuclear Power Plant (Lithuania) are discharged into cooling pond – Druksiai Lake. Submerged hydrophytes were selected as biota exposure indicators because they represent the largest biomass in this lake and have comparatively high radionuclide activity concentrations. The detailed methodology evaluation of the submerged hydrophyte dose rate is presented. The ionizing radiation exposure dose rates to submerged hydrophyte roots and above sediment parts due to the major radionuclides (54Mn, 60Co, 137Cs, 90Sr) discharged into the INPP cooling pond – Druksiai Lake were 0.044 μGy h−1 and 0.004 μGy h−1, respectively. The internal exposure dose rate due to natural background α-emitters (210Po,238U, 226Ra) was estimated to be 1.24 μGy h−1, as compared with that of anthropogenic α-emitter 240Pu – 0.04 μGy h−1, whereas the external exposure was 0.069 μGy h−1. The presented data deeper the knowledge about the concentration of radionuclides and submerged hydrophytes' exposure dose rates in European freshwater ecosystems

Assessment of radionuclide migration and radiological human exposure at the closed near-surface radioactive waste repository

The near-surface “RADON” type radioactive waste repository, installed in 1963 and designed to store radioactive waste formed in industry, medicine and scientific investigations, was closed in 1989 because it did not meet the requirements imposed on the radioactive waste disposal. A comparatively small amount of radioactive waste is stored in this repository, but the inventory comprises various kinds of waste: short-lived low-level radioactive waste, short-lived low and intermediate radioactive waste, long-lived intermediate and high-level radioactive waste. The possible site-specific radionuclide migration through the groundwater pathway as well as the human exposure are considered by the computer program RESRAD-OFFSITE in this paper. The analysis of the obtained data shows that out of all stored radionuclides only H-3, C-14 and Cl-36 exceeding the dose constraint of 0.2 mSv can be considered as dangerous. The monitoring carried out in the repository environment has shown the contamination of groundwater with radioactive tritium and a significant reduction of contamination after construction of additional protective engineering barriers. For the assessment of the contribution of separate site-specific parameters of the model taking into account uncertainties of the model and parameters to the annual effective dose, the computer code RESRAD-OFFSITE provides the possibility of applying the regression analysis. It has been determined that the aquifer lateral dispersion as well as the hydraulic gradient, the radionuclide activity concentration in the repository together with the rate of penetration into the environment and the precipitation amount have the largest influence on the assessment accuracy of annual effective doses