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Observations of new particle formation events in the south-eastern Baltic Sea

Plauškaite K., Ulevicius V., Špirkauskaite N., Byčenkiene S., Zieliński T., Petelski T., Ponczkowska A.

Oceanologia

2010

No. 52 (1)

53-75

New particle formation and growth were observed at a coastal site (Preila station, Lithuania) during 1997 and 2000-2002. The total amount of data analysed covers 291 one-day periods, 45 (15%) of which were long-term, new particle formation days. Short-term nucleation events (from a few minutes to one hour) and long-term events (from one to eight hours) were identified. The mean particle growth rate, condensation sink and condensable vapour source rate during nucleation events were 3.9 nm h*-1, 1.45 × 10*-3 cm*-3 s-1 and 7.5 x 104 cm-3 s-1 respectively. The average formation rate J_10 was 0.4 cm-3 s-1. The nucleation events were accompanied mainly by air masses transported from the north (43%) and north-west (19%). Meteorological parameters and trace gas (O3, SO2, NO2) concentrations were also analysed. It was found that nucleation events are related to high levels of solar radiation.

Plutonium and americium in sediments of Lithuanian lakes

Remeikis V., Gvozdaite R., Druteikiene R., Plukis A., Tarasiuk N., Špirkauskaite N.

Nukleonika

2005

Vol. 50, nr 2

61-66

The assessment of contribution of the global and the Chernobyl NPP (Nuclear Power Plant) accident plutonium and americium to plutonium pollution in sediments of Lithuanian lakes is presented. Theoretical evaluation of activity ratios of 238Pu/239+240Pu and 241Pu/239+240Pu in the reactor of unit 4 of the Chernobyl NPP before the accident was performed by means of the ORIGEN-ARP code from the SCALE 4.4A program package. Non-uniform distribution of radionuclides in depositions on the Lithuanian territory after nuclear weapon tests and the Chernobyl NPP accident is experimentally observed by measuring the lake sediment pollution with actinides. The activity concentration of sediments polluted with plutonium ranges from 2.0 š 0.5 Bq/kg d.w. (dry weight) in Lake Asave . lis to 14 š 2 Bq/kg d.w. in Lake Juodis. The ratio of activity concentrations of plutonium isotopes 238Pu/239+240Pu measured by á-spectrometry in the 10-cm-thick upper layer of bottom sediment varies from 0.03 in Lake Juodis to 0.3 in Lake Žuvintas. The analysis of the ratio values shows that the deposition of the Chernobyl origin plutonium is prevailing in southern and south-western regions of Lithuania. Plutonium of nuclear weapon tests origin in sediments of lakes is observed on the whole territory of Lithuania, and it is especially distinct in central Lithuania. The americium activity due to 241Pu decay after the Chernobyl NPP accident and global depositions in bottom sediments of Lithuanian lakes has been evaluated to be from 0.9 to 5.7 Bq/kg.