Laboratory study on the mobility of major species in fly ash–brine co-disposal systems: up-flow percolation test

Apart from the generation of fly ash, brine (hyper-saline wastewater) is also a waste material generated in South African power stations as a result of water re-use. These waste materials contain major species such as Al, Si, Na, K, Ca, Mg, Cl and SO4. The co-disposal of fly ash and brine has been practiced by some power stations in South Africa with the aim of utilizing the fly ash to capture the salts in brine. The effect of the chemical interaction of the species contained in both fly ash and brine, when co-disposed, on the mobility of species in the fly ash–brine systems is the focus of this study. The up-flow percolation test was employed to determine the mobility of some major species in the fly ash–brine systems. The results of the analysed eluates from the up-flow percolation tests revealed that some species such as Al, Ca and Na were leached from the fly ash into the brine solution while some species such as Mg, Cl and SO4 were removed to some extent from the brine solution during the interaction with fly ash. The pH of the up-flow percolation systems was observed to play a significant role on the mobility of major species from the fly ash–brine systems. The study showed that some major species such as Mg, Cl and SO4 could be removed from brine solution using fly ash when certain amount of brine percolates through the ash.Web of Scienc

Highway increases concentrations of toxic metals in giant panda habitat

The Qinling panda subspecies (Ailuropoda melanoleuca qinlingensis) is highly endangered with fewer than 350 individuals inhabiting the Qinling Mountains. Previous studies have indicated that giant pandas are exposed to heavy metals, and a possible source is vehicle emission. The concentrations of Cu, Zn, Mn, Pb, Cr, Ni, Cd, Hg, and As in soil samples collected from sites along a major highway bisecting the panda's habitat were analyzed to investigate whether the highway was an important source of metal contamination. There were 11 sites along a 30-km stretch of the 108th National Highway, and at each site, soil samples were taken at four distances from the highway (0, 50, 100, and 300 m) and at three soil depths (0, 5, 10 cm). Concentrations of all metals except As exceeded background levels, and concentrations of Cu, Zn, Mn, Pb, and Cd decreased significantly with increasing distance from the highway. Geo-accumulation index indicated that topsoil next to the highway was moderately contaminated with Pb and Zn, whereas topsoil up to 300 m away from the highway was extremely contaminated with Cd. The potential ecological risk index demonstrated that this area was in a high degree of ecological hazards, which were also due to serious Cd contamination. And, the hazard quotient indicated that Cd, Pb, and Mn especially Cd could pose the health risk to giant pandas. Multivariate analyses demonstrated that the highway was the main source of Cd, Pb, and Zn and also put some influence on Mn. The study has confirmed that traffic does contaminate roadside soils and poses a potential threat to the health of pandas. This should not be ignored when the conservation and management of pandas is considered

Radionuclide Incorporation in Secondary Crystalline Minerals Resulting from Chemical Weathering of Selected Waste Glasses: Progress Report for Subtask 3d

Experiments were conducted in fiscal year 1998 by Pacific Northwest National Laboratory to evaluate potential incorporation of radionuclides in secondary mineral phases that form from weathering vitrified nuclear waste glasses. These experiments were conducted as part of the Immobilized Low- Activity Waste-Petiormance Assessment (ILAW-PA) to generate data on radionuclide mobilization and transport in a near-field enviromnent of disposed vitrified wastes. An initial experiment was conducted to identify the types of secondary minerals that form from two glass samples of differing compositions, LD6 and SRL202. Chemical weathering of LD6 glass at 90oC in contact with an aliquot of uncontaminated Hanford Site groundwater resulted in the formation of a Crystalline zeolitic mineral, phillipsite. In contrast similar chemical weathering of SRL202 glass at 90"C resulted in the formation of a microcrystalline smectitic mineral, nontronite. A second experiment was conducted at 90"C to assess the degree to which key radionuclides would be sequestered in the structure of secondary crystalline minerals; namely, phillipsite and nontronite. Chemical weathering of LD6 in contact with radionuclide-spiked Hanford Site groundwater indicated that substantial ilactions of the total activities were retained in the phillipsite structure. Similar chemical weathering of SRL202 at 90"C, also in contact with radionuclide-spiked Hanford Site groundwater, showed that significant fractions of the total activities were retained in the nontronite structure. These results have important implications regarding the radionuclide mobilization aspects of the ILAW-PA. Additional studies are required to confkm the results and to develop an improved under- standing of mechanisms of sequestration and attenuated release of radionuclides to help refine certain aspects of their mobilization

SYNTHESIS OF ORGANICALLY TEMPLATED NANOPOROUS TIN (II/IV) PHOSPHATE FOR RADIONUCLIDE AND METAL SEQUESTRATION

Nanoporous tin (II/IV) phosphate materials, with spherical morphology, have been synthesized using cetyltrimethylammonium chloride (CH{sub 3}(CH{sub 2}){sub 16}N(CH{sub 3}){sub 5}Cl) as the surfactant. The structure of the material is stable at 500 C; however, partial oxidation of the material occurs with redox conversion of Sn{sup 2+} to SN{sup 4+}, resulting in a mixed Sn(II)/Sn(IV) material

Radionuclide Incorporation in Secondary Crystalline Minerals Resulting from Chemical Weathering of Selected Waste Glasses: Progress Report for Subtask 3d

Experiments were conducted in fiscal year 1998 by Pacific Northwest National Laboratory to evaluate potential incorporation of radionuclides in secondary mineral phases that form from weathering vitrified nuclear waste glasses. These experiments were conducted as part of the Immobilized Low- Activity Waste-Petiormance Assessment (ILAW-PA) to generate data on radionuclide mobilization and transport in a near-field enviromnent of disposed vitrified wastes. An initial experiment was conducted to identify the types of secondary minerals that form from two glass samples of differing compositions, LD6 and SRL202. Chemical weathering of LD6 glass at 90oC in contact with an aliquot of uncontaminated Hanford Site groundwater resulted in the formation of a Crystalline zeolitic mineral, phillipsite. In contrast similar chemical weathering of SRL202 glass at 90"C resulted in the formation of a microcrystalline smectitic mineral, nontronite. A second experiment was conducted at 90"C to assess the degree to which key radionuclides would be sequestered in the structure of secondary crystalline minerals; namely, phillipsite and nontronite. Chemical weathering of LD6 in contact with radionuclide-spiked Hanford Site groundwater indicated that substantial ilactions of the total activities were retained in the phillipsite structure. Similar chemical weathering of SRL202 at 90"C, also in contact with radionuclide-spiked Hanford Site groundwater, showed that significant fractions of the total activities were retained in the nontronite structure. These results have important implications regarding the radionuclide mobilization aspects of the ILAW-PA. Additional studies are required to confkm the results and to develop an improved under- standing of mechanisms of sequestration and attenuated release of radionuclides to help refine certain aspects of their mobilization