Metal enrichment and contamination in a karst cave associated with anthropogenic activities in the Witwatersrand Basin,South Africa     

Gerhard du Preez  Victor Wepener  Ingrid Dennis 《Environmental Earth Sciences》2016,75(8):653

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The soil leakage ratio in the Mudu watershed,China   总被引：3，自引：0，他引：3  

Xingping Wei  Yaner Yan  Deti Xie  Jiupai Ni  Hugo A. Loáiciga 《Environmental Earth Sciences》2016,75(8):721

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Kampelite,Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O,a new very complex Ba-Sc phosphate mineral from the Kovdor phoscorite-carbonatite complex (Kola Peninsula,Russia)     

Yakovenchuk  Victor N.  Ivanyuk  Gregory Yu.  Pakhomovsky  Yakov A.  Panikorovskii  Taras L.  Britvin  Sergei N.  Krivovichev  Sergey V.  Shilovskikh  Vladimir V.  Bocharov  Vladimir N. 《Mineralogy and Petrology》2018,112(1):111-121

Mineralogy and Petrology - Kampelite, Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O, is a new Ba-Sc phosphate from the Kovdor phoscorite-carbonatite complex (Kola Peninsula, Russia). It is orthorhombic, Pnma,...  相似文献   

The Effect of Key Parameters on the Strength of a Dispersive Soil Stabilized with Sustainable Binders     

Filho  Hugo Carlos Scheuermann  Martins  Carlos Guilherme  Menezes  Ricardo José Wink  Dornelles  Lucas Eduardo  Consoli  Nilo Cesar 《Geotechnical and Geological Engineering》2021,39(7):5395-5404

Geotechnical and Geological Engineering - Dispersive soils are susceptible to phenomena of internal and external erosion when in contact with relatively pure water due to its particle’s...  相似文献   

Development,urban planning and political decisions. A triad that built territories at risk     

Lara  Alejandro  Bucci  Felipe  Palma  Cristobal  Munizaga  Juan  Montre-Águila  Victor 《Natural Hazards》2021,109(2):1935-1957

Natural Hazards - Chilean geography exposes the country to high-level risks such as earthquakes and tsunamis. The disasters of 1930, 1960, 2010, and 2014 testify to the continuous link between...  相似文献   

Activity-composition relations in FeTiO3-MnTiO3 ilmenite solid solutions from EMF measurements at 1050–1300 K     

Hugh St. C. O'Neill  Mark I. Pownceby  Victor J. Wall 《Contributions to Mineralogy and Petrology》1989,103(2):216-222

The activity of FeTiO₃ in the binary ilmenitepyrophanite (FeTiO₃-MnTiO₃) solid solution has been determined for the temperature range 1050–1300 K by displacement of the reaction: 2 FeTiO₃=2 Fe+2 TiO₂+O₂ in T-O₂ space, using an electrochemical technique with calcia- and yttria-stabilized zirconia solid electrolytes. The activities show small positive deviations from ideality, which, although the data are unusually precise, may be perfectly described by the simple regular solution model, with an interaction parameter, W _Fe-Mn ^ilm , of 2.2±0.3 kJ g-atom^–1, which is independent of temperature. This value, together with the experimental data on the partitioning of Fe and Mn between ilmenite and garnet (Pownceby et al. 1987), gives W _Fe-Mn ^gt =1.2±0.5 kJ g-atom^–1 for the almandine-spessartine (Fe₃Al₂Si₃O₁₂-Mn₃Al₂Si₃O₁₂) solid solution.  相似文献   

Groundwater contamination with arsenic and other trace elements in an area of the pampa,province of Córdoba,Argentina   总被引：1，自引：0，他引：1  

Hugo B. Nicolli  Jose M. Suriano  Miguel A. Gomez Peral  Luis H. Ferpozzi  Omar A. Baleani 《Environmental Geology》1989,14(1):3-16

A geochemical study of groundwater of the pampa in the province of Córdoba, Argentina, was performed; the area covered approximately 10,000 km².Physical-chemical parameters, dissolved solids, and seven trace elements were determined in 60 selected water samples. Systematic and accurate measurements of arsenic, flourine, and vanadium were performed for the first time. Three trace element contaminants not reported earlier were found: an important one, selenium, and two others of less known effects, uranium and molybdenum.Eighty-four percent of the water analyzed showed arsenic contents over 0.05 mg/L, maximum contaminant level established by the U.S. Environmental Protection Agency (1982). The frequency distribution of trace elements was analyzed, and its fit to the lognormal distribution was proved by means of the Pearson and Kolmogorov-Smirnov test; the geographic distribution of the seven trace elements was mapped and its correlation with the anion-cation composition of the water was studied.The maximum arsenic, fluorine, vanadium, and uranium contents were found in the western part of the area under study, in waters containing dominant alkali metals in the cation composition. Maximum selenium and antimony contents were found in the eastern part of the area, while molybdenum distribution does not show any relationship with the other two groups. In addition, the geographic distribution of the trace elements seems to be related to the subsurface structure, which has been inferred using interactive digital analysis of Landsat imagery. The movements of the subsoil have disturbed surface and subsurface drainage influencing the water salinity and trace element contents.In order to investigate the origin of the contamination, 54 loess samples were collected in wells at depths ranging from the surface down to the water table. This loess, which has a high proportion of volcanic components, mainly rhyolitic glass, exhibits a chemical composition corresponding to that of a dacite.The loess and the volcanic glass show anomalous contents of all contaminant trace elements, mainly arsenic and selenium. For this reason loess is considered the most important contamination source in the groundwater under study.  相似文献   

The compressibility of silicate liquids containing Fe2O3 and the effect of composition,temperature, oxygen fugacity and pressure on their redox states     

Victor C. Kress  Ian S. E. Carmichael 《Contributions to Mineralogy and Petrology》1991,108(1-2):82-92

Ultrasonic longitudinal acoustic velocities in oxidized silicate liquids indicate that the pressure derivative of the partial-molar volume of Fe₂O₃ is the same in iron-rich alkali-, alkaline earth- and natural silicate melt compositions at 1 bar. The dV/dP for multicomponent silicate liquids can be expressed as a linear combination of partial-molar constants plus a positive excess term for Na₂O−Al₂O₃ mixing. Partial-molar properties for FeO and Fe₂O₃ components allow extension of the empirical expression of Sack et al. (1980) to permit the calculation of Fe-redox equilibrium in a natural silicate liquid as a function of composition, temperature, fo₂ and pressure; a more formal thermodynamic expression is presented in the Appendix. The predicted equilibrium fo₂ of natural silicate melts, of fixed oxygen content, closely parallels that defined by the metastable assemblage fayalite+magnetite+β-quartz (FMQ), in pressure-temperature space. A silicate melt initially equilibrated at 3 GPa and FMQ, will remain within approximately 0.5 log₁₀ units of FMQ during its closed-system ascent. Thus, for magmas closed to oxygen, iron-redox equilibrium in crystal-poor pristine glassy lavas represents an excellent probe of the relative oxidation state of their source regions.  相似文献   

用超速CT机检测99例无症状香港中国人降低钙指数     

吴敬文  戴有鼎 《CT理论与应用研究》1994,3(4):34-34

回顾分析Ｍａｔｉｌｄａ医院超速ＣＴ室筛选首批病人中９９例中国人资料，很明显从通常采用１３０－１００Ｈｏｕｎｓｆｉｅｌｄ单位作为检出冠状血管钙化的基数应用至中国人身上其阈值数目需要降低，同时，我们也发现如果病人年龄按每１０年范围分组（２１－３０，３０－４０，４１－５０，５１－６０）而计算其超速ＣＴ的钙化指数会较随机男女一起按平均计算更易区分其差异．进一步分析显示，男性中年时候超速ＣＴ指数已达最高值，而女性则晚１０年方达最高值，因此，为了更易探测冠脉循环内钙化倾向应作出超速ＣＴ检出钙化的指数数目．这些实践经验对动脉粥样硬化过程的预测或预防有实际意义．  相似文献   

The annual cycle of kiel bight plankton: A long-term analysis     

Victor Smetacek 《Estuaries and Coasts》1985,8(2):145-157

Over the past decade, the annual cycle of the major pelagic processes in relation to environmental factors and species composition of the plankton has been studied intensively at a fixed station in Kiel Bight. A series of sequential phases, differentiated according to characteristic properties, succeed each other in a recurring pattern each year. The following phases have been differentiated: the spring diatom bloom, the late spring copepod maximum, the summer stratification, the fall blooms and the winter dormancy. Each phase represents a particular pattern of biogenous element cycling, both within the pelagic system and between the pelagic and benthic systems. Each phase is also characterized by a spectrum of dominant species, many of which do not recur each year. Greatest variation is found amongst bloom diatoms, whereas large, slow-growing species such as the Ceratia and most metazooplankton are highly recurrent. Variation in species composition is not related to long-term trends since the past century, in spite of the considerable increase in anthropogenic nutrient input to the Bight. Short-term events appear to determine occurrence of fast-growing species, many of which have benthic resting stages in their life histories. It is concluded that more attention should be paid to life history strategies of species if the mechanisms of seasonal succession are to be elucidated. Long-term observations on appearance or absence of the various species in relation to environmental properties can provide clues as to the nature of these life history strategies.  相似文献