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Abstract  

Marine sediment cores were collected from two stations at East Malaysia coastal waters on June 2004. Activity concentrations of 210Pb in sediment core were ranged from 11 Bqkg−1 to 84 Bqkg−1 dry wt. for SR 01 and 4 Bqkg−1 to 66 Bqkg−1 dry wt. for SB 03. Meanwhile, activity concentrations of 226Ra in sediment core were varied significantly depending on the sampling location of SR 01 and SB 03 with ranged 17–26 Bqkg−1 dry wt. and 8–11 Bqkg−1 dry wt., respectively. The activity ratios of 210Pb/226Ra were no significantly different at all sampling stations with an average of 1.78. Refer to the entire results; the activities of 210Pb and 226Ra were higher at station SR 01 than station SB 03, but contrast with ratio of 210Pb/226Ra. The reasons of different 210Pb and 226Ra activity concentration and distribution of their ratios were strictly related to their half lives, environment origin, potential sources and behavior.

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Low-energy -ray spectrometry is used to detect fallout155Eu and207Bi in a210Pb-dated sediment core from McKay Lake, Ottawa, Canada. Unlike207Bi which is detected only in two core sections deposited in the mid 1970's,155Eu is consistently detectable to mid 1960's. A comparison of corresponding137Cs and155Eu inventories in the sediment core indicates that fallout155Eu derives primarily from the thermal neutron fission of235U. The derived flux of unsupported210Pb at the sediment/water interface is in agreement with previously estimated flux of atmospheric210Pb in the Great Lakes region.

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Abstract  

238Pu, 239-240Pu, and 241Am were measured, by -counting after radiochemical separation, in two lake sediment cores. The profiles of these transuranics were compared to those of the fission product 137Cs. Datation of nuclear events and data on behavior of the studied elements were deduced.

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Abstract  

238, 239-240Pu were measured in German lake sediment coresby counting after radiochemical separation. Their distribution over the bedof the lake was determined. The lake contain 3 basins and for each basin 3sediment cores have been sliced in two subsamples. The results show that theactivity distribution is not the same over the lake and that the sedimentationrate changes in the 3 basins.

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A radioactively contaminated marine sediment core stemming from Irish Sea has been characterized by radiometric and mass spectrometric techniques as for 237Np, 241Am, 239Pu, 240Pu, 241Pu, 137Cs and 154Eu. The data obtained with independent methods in the framework of a QA/QC program as compared with the source term discharges, as well as with those reported in literature, are in good agreement.

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The activity concentration of natural radionuclides and 137Cs in the bottom sediments cores from Kuwait Bay have been determined by γ-ray spectrometry. Particular attention was devoted to the exact determination of two uranium isotopes: 235U and 238U in order to find any presence of depleted uranium dispersed during the 1991 Gulf War. The calculated 238U/235U activity ratios for all the surface (15 cm) as well as the core profile (up to 70 cm in depth) samples were within the limit of one standard deviation close to the value of 21.5 for natural uranium. Simultaneous instrumental determination of the unsupported 210Pb and 226Ra in a few sediment core profiles was used for quantification of sediment accumulation rates. The calculated sedimentation rates (for the constant atmospheric 210Pb flux rate - CRS model) ranged from 0.2 to 0.6 cm . y-1 and were close to the data calculated by the Weibull distribution of 137Cs in undisturbed sediment cores.

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Abstract  

Sediment core samples taken from the Jinheung catchment located in the middle of the Korean Peninsula were used to know environmental radionuclide distribution. The grain sizes of the sediment cores were found at depth of about 17 cm suggesting that it might have occurred during a dry period of 1969. The radionuclides, 137Cs, 237Np, 239Pu, 240Pu, 234U, 238U, 228Th, 230Th, 232Th, were analyzed by sector type ICP-MS and gamma-spectrometry. The Cs and Pu distribution changed with the depth, in which the maximum ranged from 14 to 22 cm. This was due to the high activity of the results of nuclear bomb tests in the air from 1960s and showed different distribution pattern on the soil surface. The average activity ratio of 240Pu/239Pu and 237Np/239Pu was 0.173 and 0.45, respectively. These values were similar to the north hemisphere global fallout ratio of 240Pu/239Pu (0.18) and 237Np/239Pu (0.45). The 237Np/239Pu ratio showed a higher value than the global fallout ratio above 14 cm depth. The U, Th and their daughter radionuclides kept secular equilibrium in the sediment core because the average activity ratios were nearly 1.

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Guanabara Bay, located at Rio de Janeiro, is an example of an impacted coastal environment due to the high influx of industrial and domestic effluents. Four sediment cores were sampled in areas with different levels of pollution and were analyzed for trace elements and foraminifera for abundance. Instrumental neutron activation analysis (INAA) was used to determine As, Ba, Co, Cr, Fe, Sb, Sc, and Zn. The effects of metal concentrations in the benthic foraminifera were studied. The low concentrations of the benthic foraminifera and the dominance of opportunistic species in coastal regions such as Ammonia may be correlated to natural stress or anthropogenic impact.

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The diatoms of bottom sediment core samples were studied from Lake Balaton. During the 1980s altogether 33 boreholes were drilled into the Quaternary layers down to 10-12 m. This paper presents the diatom flora and vegetation of 17 boreholes based on the legacy of Márta Hajós who spent 16 years working on this subject. The enumeration contains occurrences of 385 diatom taxa. It is hoped that this scientific account will serve as a “diatom databank” and helps better understanding of recent environmental changes in the larger area.

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Abstract  

Measurements of210Pb at various dephts in a sediment core from the Santa Cruz Basin off the coast of California have been made. The radiochemical separation of210Pb was carried out after ashing the sediment at 400 °C. The activities of the purified210Pb was assayed in a low background beta counter by counting the 1.17 MeV betas of its daughter product210Bi. The method for the chemical separation of210Pb and the results are discussed in the paper.

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