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1.
Sheppard PR Speakman RJ Ridenour G Witten ML 《Environmental monitoring and assessment》2007,130(1-3):511-518
This paper describes the use of lichen chemistry to assess airborne tungsten and cobalt in Fallon, Nevada, where a cluster
of childhood leukemia has been on going since 1997. Lichens and their rock substrates were collected from Rattlesnake Hill
within Fallon as well as from four different rock outcrops located north, east, south, and west of Fallon and at least 20 km
away from the town center. In the lichens themselves, W and Co are significantly higher within Fallon than in the combined
control site outside of Fallon. In the rock substrates of the lichens, no differences exist in W and Co. The W and Co differences
in lichens cannot be attributed to substrate geochemistry. Fallon is distinctive in west central Nevada for high airborne
W and Co, and given its cluster of childhood leukemia, it stands to reason that additional biomedical research is in order
to test directly the leukogenicity of combined airborne W and Co. 相似文献
2.
Sorption of tungstate on boehmite(γ-Al OOH)is increased by co-sorption with Co~(2+)over the near-neutral p H range.Batch uptake experiments show up to a 3-fold increase in tungstate uptake over the range WO_4~(2-)=50–1000μmol/L compared to boehmite not treated with Co~(2+).Desorption experiments reveal a corresponding decrease in sorption reversibility for tungstate co-sorbed with Co~(2+).Reaction of boehmite with Co~(2+)results in the formation of Co Al layered double hydroxide(LDH),as confirmed by X-ray diffraction and X-ray absorption spectroscopy.Tungsten L_3-edge X-ray absorption near edge structure(XANES)reveals that W(VI)is octahedrally coordinated in all sorption samples,with polymeric tungstate species forming at higher tungstate concentrations.X-ray diffraction and X-ray absorption spectroscopy indicate that the mechanism for enhancement of tungstate uptake is the formation of surface complexes on boehmite at low tungstate concentrations,while exchange into the Co Al LDH becomes important at higher tungstate concentrations.The results provide a basis for developing strategies to enhance tungstate sorption and to limit its environmental mobility at near-neutral pH conditions. 相似文献
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4.
Nissen S Alexander BD Dawood I Tillotson M Wells RP Macphee DE Killham K 《Environmental pollution (Barking, Essex : 1987)》2009,157(1):72-76
Photoelectrocatalysis driven by visible light offers a new and potentially powerful technology for the remediation of water contaminated by organo-xenobiotics. In this study, the performance of a visible light-driven photoelectrocatalytic (PEC) batch reactor, applying a tungsten trioxide (WO3) photoelectrode, to degrade the model pollutant 2,4-dichlorophenol (2,4-DCP) was monitored both by toxicological assessment (biosensing) and chemical analysis. The bacterial biosensor used to assess the presence of toxicity of the parent molecule and its breakdown products was a multicopy plasmid lux-marked E. coli HB101 pUCD607. The bacterial biosensor traced the removal of 2,4-DCP, and in some case, its toxicity response suggests the identification of transient toxic intermediates. The loss of the parent molecule, 2,4-DCP determined by HPLC, corresponded to the recorded photocurrents. Photoelectrocatalysis offers considerable potential for the remediation of chlorinated hydrocarbons, and that the biosensor based toxicity results identified likely compatibility of this technology with conventional, biological wastewater treatment. 相似文献
5.
Sheppard PR Speakman RJ Ridenour G Glascock MD Farris C Witten ML 《Environmental geochemistry and health》2007,29(5):405-412
Spatial patterns of tungsten and cobalt are described for surface dust of Fallon, Nevada, where a cluster of childhood leukemia
has been ongoing since 1997. In earlier research, airborne tungsten and cobalt was shown to be elevated in total suspended
particulates in Fallon. To fine-tune the spatial patterns of tungsten and cobalt deposition in Fallon, surface dust was collected
in a grid pattern within as well as outside of Fallon to establish background concentrations of metals. In surface dust, tungsten
and cobalt show sharp peaks (934 ppm and 98 ppm, respectively) within Fallon just north of highway 50 and west of highway
95. These two peaks overlap spatially, and given the grid pattern used for collecting surface dust, the source area of these
two airborne metals can be pinpointed to the vicinity of hard-metal industry located north of highway 50 and west of highway
95. Fallon is distinctive in west central Nevada because of high airborne tungsten and cobalt particulates, and given its
cluster of childhood leukemia, it stands to reason that additional biomedical research is in order to test directly the leukogenicity
of combined airborne tungsten and cobalt particulates. 相似文献
6.
建立了一种对土壤中钼、钨元素同时进行快速准确测定的方法。土壤样品经微波消解处理后,用电感耦合等离子体质谱法进行测定,同传统测试方法相比该方法更加简单易于操作,而且该方法检测结果准确度高,精密度好。 相似文献
7.
Physical changes that occur on the surface of fired shots due to firing and impact with soil may increase the dissolution of muniton metals. Increased metal dissolution could potentially increase metal transport and leaching, affecting metal concentrations in surface and groundwater. This research describes the relationship between the surface changes on fired tungsten-nickel-iron (94% W:2% Ni:4% Fe) composite shots and metals leaching from those shots. Tungsten composite shot was fired into, and aged in, three soil types (Silty Sand, Sandy Clay, and Silt) in mesoscale rainfall lysimeters to simulate live-fire conditions and subsequent interactions between the metals of the composite and soil. Leachate, runoff, and soil samples were collected from the lysimeters and analyzed for metal content. The shots were analyzed using scanning electron microscopy (SEM) to evaluate surface changes. SEM results indicated that a soil’s particle size distribution initially affected the amount of metal that was sheared from the surface of the fired W-composite shots. Shearing was greatest in soils with larger soil particles (sand and gravel); shearing was least in soils composed of small soil particles (fines). Increased metallic shearing from the shot’s surface was associated with increased W dissolution, compared to controls, following a simulated 1 year soil aging. 相似文献
8.
《Journal of Manufacturing Processes》2014,16(2):296-304
The objective of this research is to investigate the mechanical properties including bonding, tensile strength, and impact resistance of pure copper welded using friction stir welding (FSW) method and compare them with that of tungsten inert gas (TIG) welding. Micro-hardness tests are performed on pure copper, TIG welded copper and FSW welded copper to determine the effect of heat on the hardness of welded coppers. Tensile strength tests and notch tensile strength tests are performed to determine the mechanical properties of different weld process.In this experiment, it is found that the notch tensile strength and the notch strength ratio for FSW (212 MPa, 1.10) are significantly higher than those (190 MPa, 1.02) of TIG welding. For the impact tests, the weld zone and heat-affected zone energy absorption values for FSW (2.87 J, 2.25 J) are higher than those (1.32 J, 0 J) of TIG welding. XRD tests are performed to determine components of copper before and after welding process for TIG and FSW. 相似文献
9.
关于钨冶炼收尘装置的研究 总被引:1,自引:0,他引:1
本文是关心钨冶炼收尘装置的研究,文章主要就钨精矿焙烧的收尘问题提出了一种新的收尘设备,使钨精矿焙烧的收尘效率达到99%。 相似文献
10.
粤东燕山期与成矿有关的火成岩主要有早、晚两期,分别由火山岩与二长花岗岩及火山岩与黑云母花岗岩组成,两期的火山岩与花岗岩之间均为部分熔融关系,早期火成岩的源岩以沉积岩为主,晚期火成岩以火成物质占优势。锡矿化可划分为锡石—石英期次、锡石—硫化物期次及硫化物—银、金—碳酸盐期次;钨矿化可分为黑钨—石英期次,白钨—硫化物期次及碳酸盐期次。据系统的矿物包裹体,成矿热力学、成因矿物学、微量元素及同位素地球化学研究表明其成矿流体及成矿物质主要来自花岗岩,锡的矿化与早期二长花岗岩有关,钨矿化与晚期黑云母花岗岩关系密切。矿床成因类型应属岩浆—热液矿床。 相似文献