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Papers by Constantin Cosma
Journal of Environmental Radioactivity, 2013
Radon contributes to over than 50% of the natural radiation dose received by people. In radon ris... more Radon contributes to over than 50% of the natural radiation dose received by people. In radon risk areas this contribution can be as high as 90e95%, leading to an exposure to natural radiation 5e10 times higher than normal. This work presents results from radon measurements (indoor, soil and exhalation from building materials) in B ait¸a-Ş tei, a former uranium exploitation area in NW Romania. In this region, indoor radon concentrations found were as high as 5000 Bq m À3 and soil radon levels ranged from 20 to 500 kBq m À3 . An important contribution from building materials to indoor radon was also observed. Our results indicate two independent sources of indoor radon in the surveyed houses of this region. One source is coming from the soil and regular building materials, and the second source being uranium waste and local radium reached material used in building construction. The soil as source of indoor radon shows high radon potential in 80% of the investigated area. Some local building materials reveal high radon exhalation rate (up to 80 mBq kg À1 h À1 from a sandy-gravel material, ten times higher than normal material). These measurements were used for the radon risk classification of this area by combining the radon potential of the soil with the additional component from building materials. Our results indicate that B ait¸a-Ş tei area can be categorized as a radon prone area.
Geochronometria, 2011
The biggest problem with most lakes that have no contact with other water sources and are being c... more The biggest problem with most lakes that have no contact with other water sources and are being charged by precipitation is the massive eutrophication. The aim of this work was to determine the sedimentation rate in order to evaluate the progress of eutrophication for St. Ana Lake (Ciomad Mountain near the Băile Tuşnad in Harghita County (Romania)). The concentration of 210 Pb was determined by means of high resolution gamma spectrometry as well as derived from 210 Po activity which was measured through alpha spectrometry; values obtained are in good agreement. For the excess 210 Pb activity values between 4.0±0.5 Bq/kg and 218±20 Bq/kg have been found. As an alternative method, the 137 Cs dating method was applied as well. Calculated mass sedimentation rates are in the range of 0.06±0.01 to 0.32±0.05 g/cm 2 year with a mean of value of 0.15±0.02 g/cm 2 year. Linear sedimentation rates yielded much higher sedimentation values (between 0.5±0.1 and 7.9±0.7 cm/year with a mean of 2.4±0.6 cm/year), due to the predominant organic matter composition and the long suspension time of the sediment. This is an indication for the process of eutrophication which will probably lead to the transformation of the lake into a peat bog.
Journal of Environmental Radioactivity, 2016
Airborne (137)Cs originated from the nuclear tests in the atmosphere and from the Chernobyl nucle... more Airborne (137)Cs originated from the nuclear tests in the atmosphere and from the Chernobyl nuclear disaster was retained by the trees biomass and nowadays it can still be found in various concentrations in tree barks from Romania and other European countries. This study brings the first results of (137)Cs presence in tree bark from Romania on different considerations: (i) data dispersion in spruce and oak bark from NW, SW and central Romania, and the spatial variability of (137)Cs within oak and spruce bark from a natural protected forest area from Balvanyos area (Covasna County), known to be highly affected by the Chernobyl nuclear release; (ii) comparison of (137)Cs content in different tree bark species (oak, spruce, poplar and cherry); (iii) differences in (137)Cs concentrations with the bark depth layers and around the tree trunk; and (iv) comparison of mean (137)Cs values in spruce/oak bark from Romania with data from other European countries.
Spectrochim Acta Pt B at Spec, 2002
In a previous paper a study of the supported nickel catalysts based on extended X-ray absorption ... more In a previous paper a study of the supported nickel catalysts based on extended X-ray absorption fine structure spectroscopy was presented for analysis of the first coordination shell. The present study evidenced a strong deformation of the local structure of the metal due to its interaction with oxide support. The average particle size, microstrains and probability of faults, the particle size distribution function of supported Ni catalysts were determined by X-ray diffraction method. The method is based on Fourier analysis of experimental X-ray line profile (1 1 1), (2 0 0) and (2 2 0). The global structure is obtained with a fitting method based on the generalized Fermi function facilities for approximation. A chemisorption model was elaborated by correlation of the local and global structure connected with the specific surface areas. The results obtained on supported Ni catalysts which are used in H/D isotopic exchange reactions are reported. Both types of measurements were performed on the Beijing synchrotron radiation facilities.
Revista Româna De Materiale, 2009
Il Nuovo Cimento C
ABSTRACT
Journal of Environmental Radioactivity, 2013
Radon contributes to over than 50% of the natural radiation dose received by people. In radon ris... more Radon contributes to over than 50% of the natural radiation dose received by people. In radon risk areas this contribution can be as high as 90e95%, leading to an exposure to natural radiation 5e10 times higher than normal. This work presents results from radon measurements (indoor, soil and exhalation from building materials) in B ait¸a-Ş tei, a former uranium exploitation area in NW Romania. In this region, indoor radon concentrations found were as high as 5000 Bq m À3 and soil radon levels ranged from 20 to 500 kBq m À3 . An important contribution from building materials to indoor radon was also observed. Our results indicate two independent sources of indoor radon in the surveyed houses of this region. One source is coming from the soil and regular building materials, and the second source being uranium waste and local radium reached material used in building construction. The soil as source of indoor radon shows high radon potential in 80% of the investigated area. Some local building materials reveal high radon exhalation rate (up to 80 mBq kg À1 h À1 from a sandy-gravel material, ten times higher than normal material). These measurements were used for the radon risk classification of this area by combining the radon potential of the soil with the additional component from building materials. Our results indicate that B ait¸a-Ş tei area can be categorized as a radon prone area.
Geochronometria, 2011
The biggest problem with most lakes that have no contact with other water sources and are being c... more The biggest problem with most lakes that have no contact with other water sources and are being charged by precipitation is the massive eutrophication. The aim of this work was to determine the sedimentation rate in order to evaluate the progress of eutrophication for St. Ana Lake (Ciomad Mountain near the Băile Tuşnad in Harghita County (Romania)). The concentration of 210 Pb was determined by means of high resolution gamma spectrometry as well as derived from 210 Po activity which was measured through alpha spectrometry; values obtained are in good agreement. For the excess 210 Pb activity values between 4.0±0.5 Bq/kg and 218±20 Bq/kg have been found. As an alternative method, the 137 Cs dating method was applied as well. Calculated mass sedimentation rates are in the range of 0.06±0.01 to 0.32±0.05 g/cm 2 year with a mean of value of 0.15±0.02 g/cm 2 year. Linear sedimentation rates yielded much higher sedimentation values (between 0.5±0.1 and 7.9±0.7 cm/year with a mean of 2.4±0.6 cm/year), due to the predominant organic matter composition and the long suspension time of the sediment. This is an indication for the process of eutrophication which will probably lead to the transformation of the lake into a peat bog.
Journal of Environmental Radioactivity, 2016
Airborne (137)Cs originated from the nuclear tests in the atmosphere and from the Chernobyl nucle... more Airborne (137)Cs originated from the nuclear tests in the atmosphere and from the Chernobyl nuclear disaster was retained by the trees biomass and nowadays it can still be found in various concentrations in tree barks from Romania and other European countries. This study brings the first results of (137)Cs presence in tree bark from Romania on different considerations: (i) data dispersion in spruce and oak bark from NW, SW and central Romania, and the spatial variability of (137)Cs within oak and spruce bark from a natural protected forest area from Balvanyos area (Covasna County), known to be highly affected by the Chernobyl nuclear release; (ii) comparison of (137)Cs content in different tree bark species (oak, spruce, poplar and cherry); (iii) differences in (137)Cs concentrations with the bark depth layers and around the tree trunk; and (iv) comparison of mean (137)Cs values in spruce/oak bark from Romania with data from other European countries.
Spectrochim Acta Pt B at Spec, 2002
In a previous paper a study of the supported nickel catalysts based on extended X-ray absorption ... more In a previous paper a study of the supported nickel catalysts based on extended X-ray absorption fine structure spectroscopy was presented for analysis of the first coordination shell. The present study evidenced a strong deformation of the local structure of the metal due to its interaction with oxide support. The average particle size, microstrains and probability of faults, the particle size distribution function of supported Ni catalysts were determined by X-ray diffraction method. The method is based on Fourier analysis of experimental X-ray line profile (1 1 1), (2 0 0) and (2 2 0). The global structure is obtained with a fitting method based on the generalized Fermi function facilities for approximation. A chemisorption model was elaborated by correlation of the local and global structure connected with the specific surface areas. The results obtained on supported Ni catalysts which are used in H/D isotopic exchange reactions are reported. Both types of measurements were performed on the Beijing synchrotron radiation facilities.
Revista Româna De Materiale, 2009
Il Nuovo Cimento C
ABSTRACT