Carbon-14 in Tree Rings in the Vicinity of Ignalina Nuclear Power Plant, Lithuania
The results of 14C measurements in the annual tree rings from the Ignalina Nuclear Power Plant (INPP) vicinity, Lithuania, for the period of its operation from 1984 to 2002 are presented. The terrestrial samples, mainly moss and related topsoil, are studied in places as well. The tree rings have shown the slightly enhanced 14C activity due to operation of the nuclear power plant. The maximal calculated normalized 14C release of 11 TBq/GWe/year and the maximal effective dose of 2.0x10-3 mSv/year resulting from the 14C were estimated for 1999. The excess of 14C specific activity measured in the moss and soil samples from moss-covered sites near the nuclear power plant (up to 0.5 km) showed highly elevated 14C contents (up to 813 pMC), probably indicating releases of the particulate material.
Investigations of soil erosion by 137Cs method brings uncertainties of different nature. The estimation of the 137Cs local inventory is associated with problems of data comparison and instrumental errors. In order to avoid systematic errors, the rate of soil erosion determined by the 137Cs method is compared with the values obtained for other radioactive elements. Soil parameters must be regarded too. The aim of the work was to test the character of 137Cs and 40K distribution in the topsoil vertical section for determination erosion-accumulation type and ratio in different time spans. The topsoil thickened by different types of erosion-accumulation processes was sampled at a 2–3 cm interval. Soil samples were analysed by means of scintillation gamma spectrometry. The relationship between 137Cs and 40K inventories was weakest in the topsoil formed by mixing of soil material during the installation of artificial drains. Based on climatic characteristics, variations of theoretical soil accumulation rate in the last 50 years were calculated for the topsoil accumulated predominantly by water erosion. 40K and 137Cs correlation in the bottom of vertical section of topsoil or arable horizon are closest and this section may be used as a complementary parameter determining the local inventory value.
The sediments of two lakes located in the Baltic Uplands, the western part of the East European Plain (East Lithuania and North East Poland), were studied. Activity concentration of 210Pb was determined using two nuclear analytical techniques: determination of 210Pb in equilibrium with its beta emitting daughter 210Bi using liquid scintillation counter (LSC), and direct determination of 210Pb (and other radionuclides) by low-background gamma-ray spectrometer with a well type HPGe detector. For the 210Pb determination by LSC the methodology of lead separation based on the anion exchange resin in Cl– form (Eichrom) was used. Several steps of radiochemical procedures and respective parameters were investigated additionally. The optimized procedures for LSC method were used for case study with two lake cores. The activity concentration of 210Pb in lake sediment samples based on both nuclear analytical techniques (LSC and HPGe) were compared. 210Pb dating of cores was performed according to Constant Rate of 210Pb Supply (CRS) model with some modifications. Both techniques in the range of uncertainties gave similar results. From two considered lakes, the more eutrophic one exhibited higher sediment mass accumulation rate (MAR) values.
The Use of Carbon-14 and Tritium For Peat and Water Dynamics Characterization: Case of Čepkeliai Peatland, Southeastern Lithuania
The present investigation conducted in Čepkeliai peatland (south-eastern Lithuania) deals with two radioisotope methods - carbon-14 (14C) and tritium (3H). 14C was applied to peatland chronology and sedimentation rate estimation and 3H to peat water dynamics characterization. According to 14C data, peatland development began since 12650-11350 years cal BP and peat accumulation since 10550-9700 years cal BP with peat accumulation rate of 0.27-0.79 mm/year in the central part of the peatland. The peat water mean residence time and basic groundwater flow was estimated to be respectively about 27±6 years and 62±15 mm based on 3H data. The obtained data showed relatively undisturbed natural condition of Čepkeliai peatland in the studied sites.
Sub-fossil oaks from Smarhoń in Belarus have been investigated and tree-ring chronologies were assembled. According to radiocarbon dating, the oldest oak grew from 5782–5612 cal BC and the youngest from 1575–1747 cal AD. Radiocarbon and dendrochronological dating of 97 samples, four single series, 10 mean curves (containing 2–9 series) and three chronologies (10–25 series) were constructed. The longest chronology (No. 16), covering 549 years, was absolutely dated against various oak chronologies of Polish/Baltic origin to AD 778–1326. Germination and dying-off phases were assessed from the three best replicated chronologies. A spectral analysis of the chronologies provided cycles of variable length, on average of 25 years.
Reconstruction of past anthropogenic impact intensity in Lake Engure using sedimentary record analysis
Environmental pollution with trace elements is considered as one of the most important environmental problems. Analysis of trace element accumulation in sedimentary phases of lakes may reflect the overall regional pollution level, and analysis of trace element accumulation patterns in sediment profiles can help to reconstruct the history of anthropogenic impact. The aim of this study was to analyse trace element concentrations in sediments of Lake Engure in Latvia and to determine factors influencing their availability. The metal concentrations in sediments of Lake Engure are at background levels, especially compared with metal concentrations in West European countries. However, the change in element concentration in sedimentary profiles provides information about trends of recent accumulation (within the last 100 years) and on the balance between natural and human-induced accumulation processes.