Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Nukleonika

2 Kownacka L.

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: transport in the atmosphere

Sortuj według:

Ogranicz wyniki do:

Vertical distributions of beryllium-7 and lead-210 in the tropospheric and lower stratospheric air

Kownacka L.

Nukleonika

2002

Vol. 47, nr 2

79-82

Vertical distributions of 7Be and 210Pb were observed in the troposphere and lower stratosphere over Poland at several altitudes between 0 and 15 km in the period 1987-1998. These two natural radionuclides are formed from gases in the atmosphere by nuclear processes. They are associated with similar size distributions aerosol particles and are removed from the atmosphere with similar efficiencies by scavenging processes of washout and deposition, however, they have various types of sources in the atmosphere. Vertical profiles of 7Be (cosmogenic origin), characterized by small concentrations near the ground level, increase in the tropospheric levels and at 15 km altitude the concentrations are the highest. The highest concentrations of 210Pb (terrestrial origin) are observed near the ground level, the lowest are below the tropopause, and in the stratosphere the concentration increases slightly. The dependence of the vertical distributions of both radionuclides in the situation of various levels of tropopause are discussed in this work.

Natural and artificial radionuclides in the tropospheric and lower stratospheric air over Poland

Kownacka L.

Nukleonika

2001

Vol. 46, nr 4

175-177

The high altitude aircraft sampling of aerosols have been carried out at four to seven levels up to 15 km over Poland from 1973 to 1998, and 117 vertical concentration profiles of natural radionuclides and fission products were determined. It was found that the atmospheric concentrations of 226Ra increased after large volcanic eruptions. The vertical concentrations profile of 226Ra had a characteristic quasi-parabolic distribution, with the highest concentrations near the ground level and in the stratosphere. Concentrations of 210Pb had a more homogeneous vertical distribution, due to the quiescent ascent of its gaseous 222Rn precursor from the ground. Vertical concentrations of fission products revealed different types of profiles. After nuclear explosions, the highest concentrations were observed in the stratosphere. The Chernobyl accident reversed the aerial vertical profiles; the main source was near the ground level, but part of the radioactive debris entered also the lower stratosphere. Because of resuspension, the stratospheric residence time of radiocesium from the Chernobyl accident was about three times longer than that of the fallout from nuclear explosions. The resuspension effects and the atmospheric mass transport in the boundary layers are also responsible for the increased concentrations of radiocesium at 1 km altitude observed since 1987 in the situations of atmospheric mass advection from the highly contaminated Chernobyl region.