14 1 1 9 50 pd 49 4 148 ag 4 19 1 5 4 50 cd 11 263 2

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14 1 1 9 50 Pd - - 49 - - 4 148 Ag 4 - 19 1 5 4 50 Cd 11 - 263 2 46 32 723 Sn 197 21 9 6 11 115 1591 Sb 7 33 61 2 5 19 291 Cs 7 21 17 2 3 11 99 Ba 486 3284 173 47 92 1182 12160 La 13 3 21 4 5 10 59 Ce 38 5 56 4 10 27 187 Pb 605 78 6652 36 189 964 16570 The concentrations were calculated using the MC based quantification method. Five clusters were obtained using HCA bulk XRF. As it is shown in Table 7.19, Clusters 2 and 4 can be regarded as natural sediment particles, because they were formed from particles with very low copper, zinc, and lead content. A comparison of simulated and measured X-ray spectra of a typical sediment particle classified to Cluster 2 is presented in Fig. 7.124, showing good agreement. The particles however, which could be associated with the mine pollution accident (Clusters 1, 3, and 5), contained La, Ce, and Nd also in an order of magnitude higher than natural sediment particles [378]. 7.5.5 Radionuclides and Radioactive Materials Radionuclides may be introduced into the environment through a variety of systems and processes. Human activities involving nuclear weapons and nu- clear fuel cycle (including mining, milling, fuel enrichment, fabrication, reac- tor operation, spent fuel stores, reprocessing facilities, medical applications and waste storage) are important, leading to a significant creation and re- lease of radioactivity. Human technology also releases pre-existing natural
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636 S. Kurunczi et al 10 100 1000 10000 100000 0 5 10 15 20 25 30 35 40 Energy (keV) Intensity (counts) Experiment Simulation Ca Fe Zn Pb Rb Zr Ba Ba Ag Sn Ce Fig. 7.124. Measured and simulated white-beam micro-XRF spectra of a typical surface sediment particle collected from the Tisza main riverbed. The diameter of the particle is 60 µ m. Reproduced from Os´an et al. [378] by permission of Elsevier Science B.V. radionuclides, which would otherwise remain trapped in the earth’s crust. For instance, burning of fossil fuel (oil and coal) dominates direct atmospheric release at pre-existing natural radioactivity The fallout distribution pattern depends on the weather conditions (i.e., wet or dry). Variation in the degree of interception of fallout is found depend- ing on the nature of the surface and the physical–chemical form of radionuclide which may vary, depending on release and transport conditions in addition to elements’ properties. A general distinction can be made between gases, aerosol, and particulate material. Particles with higher activity concentration, known as “hot particles”, may result from atmospheric nuclear weapon tests or nu- clear reactor accidents. This activity is diluted as material is transferred to soil and water directly or via vegetation and movement through other biota. The ability to develop adequate models for predicting the fate of inor- ganic contaminants, including radionuclides, in both surface and subsurface environments, is highly dependent on accurate knowledge of the partitioning of these constituents between the solid and solutions phases and ultimately on the capability to provide molecular-level information on chemical species distributions in both theses phases. Furthermore, the development of environ-
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  • Spring '14
  • MichaelDudley

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