| Abstract [eng] |
Radiocarbon (14C) is a long-lived carbon isotope that has a half-life of 5730 ± 40 years. Nuclear power plants are one of the main producers of anthropogenic 14C. Anthropogenic radiocarbon can be released into the environment in gaseous forms, with liquid releases or with spent nuclear fuel. Despite this pollution is not significant in the sense of population exposure doses, but it is a significant 14C increase above background effect that allows the use it as an anthropogenic contamination tracer to study the dissemination, accumulation, and dynamics redistribution processes of the pollutant in ecosystem. The reservoir effect (RE) is defined as the difference between the radiocarbon isotope ratio (14C/12C) in the terrestrial and aquatic systems. Both natural processes and anthropogenic activities affecting carbon cycling in the water ecosystem can lead to changes in the RE. Therefore, reservoir effect studies can help to assess the impact of external factors on a hydrological system. The aim of this research was to evaluate the impact of anthropogenic 14C contamination from Ignalina nuclear power plant (Ignalina NPP, INPP) on the Lake Drūkšiai system. The lake sediment and fish (both benthic and pelagic) scale samples were collected from the Drūkšiai lake. ABA (acid-base-acid) chemical pretreatment procedure was used to extract humin (HM) and humic acid (HA) fractions from the sediments. Radiocarbon measurements in these samples were performed using the accelerator mass spectrometer. In 1963, increased concentrations of radiocarbon due to testing of nuclear weapons showed that CO2 exchange accounted for about 22% carbon in bottom sediments. During the first 15 years of operation of the Ignalina Nuclear Power Plant, 14C-enriched dissolved inorganic carbon (DIC) was continuously released into Lake Druksiai. During that period, an average of about 0.24 GBq of radiocarbon was released per year. Measurements of radiocarbon concentrations in fish confirm that the 14C contamination was in dissolved inorganic carbon form. Around 2000, 14C-enriched DIC (2.3 GBq radiocarbon) was released into Lake Druksiai from Ignalina NPP. In addition, organic compounds that were not a source of 14C but affected the interaction between humic and humic acids were additionally released in the same year. Almost a decade after the end of operation of the Ignalina NPP, there is still some 14C pollution (from INPP) remaining in Lake Druksiai. - the concentration of radiocarbon in the bottom sediments is still higher than in the atmosphere. . |
