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991.
V Sanfelix ET Gòmez MM Jordán T Sanfeliu S Pallarés AB Vicente 《Environmental Geology》2005,47(6):811-819
The objective of this work is to assess the concentrations of three factions of air particles (settable particles, TSP and PM10) and the levels of several toxic elements in a clay atomisation industry through aerosol sampling at several points inside an industrial plant. Mechanical activities, which produce diffuse emissions, are the main process of discharge of particles in both indoor and outdoor workplace environments in the atomisation plant. The levels of As, Cd, Pb, Zn, Ba and Ni increase in the zones with higher concentrations of particles and lower ventilation. The concentrations of As and F are not influenced by the recycling processes. The levels of Cd and Pb do not show great enrichment in air particles collected inside the atomisation plant although the content of both elements is associated with ceramic muck recycling. Finally, the content of B in waste water is mainly transferred in gaseous phase to the atmosphere during the process of drying by atomisation. 相似文献
992.
Craig T. Simmons 《Hydrogeology Journal》2005,13(1):116-119
993.
T. F. Zimmie A. Pamuk K. Adalier M. B. Mahmud 《Geotechnical and Geological Engineering》2005,23(4):447-459
A series of geotechnical centrifuge physical modeling tests were performed to assess the potential use of a new cost-effective mechanically stabilized earth system for retrofitting marginally stable cohesive slopes. The proposed system utilizes the dual functions of reinforcement and drainage by directly inserting high strength non-woven geotextile strips into slopes, with little or no excavation required behind the slope face. The system significantly increases the factor of safety of potentially unstable cohesive slopes, and can be constructed at less expense and more rapidly than conventional mechanically stabilized earth systems. 相似文献
994.
995.
B. A. Elliott W. H. Peck O. T. Rämö M. Vaasjoki M. Nironen 《Mineralogy and Petrology》2005,85(3-4):223-241
Summary Oxygen isotope ratios of igneous zircon from magmatic rocks in Finland provide insights into the evolution and growth of the
Precambrian crust during the Svecofennian orogeny. These data preserve magmatic δ18O values and correlate with major discontinuities in the lower crust. Oxygen isotope ratios of zircon across the 1.88–1.87 Ga
Central Finland granitoid complex (CFGC) range from 5.50‰ to 6.84‰, except for three plutons in contact with the adjacent
greenstone and metasedimentary belts (δ18O(Zrc) = 7.60‰–7.78‰). There is a systematic variation in δ18O(Zrc) with respect to geographic location in the CFGC, ranging from 6.60±0.23‰ (σ) in the northeast to 5.90±0.40‰ in the
west-southwest. These values correlate with a change in crustal thickness and shift in geochemical composition. The oxygen
isotope composition of the 1.65–1.54 Ga rapakivi granites and related rocks in southern Finland show a decreasing trend from
north to south, independent of their emplacement age. The southern anorogenic granite group has an average δ18O in zircon of 6.14±0.07‰ and the northern anorogenic group has an average δ18O in zircon of 8.14±0.59‰. This difference reflects the boundary between island arc terrains accreted during the Paleoproterozoic.
Deceased 相似文献
996.
997.
R.M. Hernndez T.E. Jordan A. Dalenz Farjat L. Echavarría B.D. Idleman J.H. Reynolds 《Journal of South American Earth Sciences》2005,19(4):495-512
Marine transgression onto the South American continent took place at least twice in the Miocene along distinct paleogeographic corridors. The first event occurred between 15 and 13 Ma and the second between 10 and 5? Ma. Each event has particular dominant variables (tectonism, eustacy, sediment accumulation rate) that permitted the preservation of the record and development of the sea on the continent. The 15–13 Ma transgression was tectonically and eustatically controlled, flooding older sedimentary accommodation zones on the South American plate during a global high sea level, whereas the 105? Ma event was predominantly tectonically controlled, generated by tectonic loading created in the Cordillera Oriental fold-and-thrust belt. A new 7.72±0.31 Ma 40Ar/39Ar date from the Río Parapetí in Bolivia suggests that the 15–13 Ma transgression registered in Argentina produced no continental connection to the Caribbean transgression, registered in Bolivia, because of temporal constraints. 相似文献
998.
M. S. Rahbar T. Kaghazchi 《International Journal of Environmental Science and Technology》2005,2(3):207-215
Development of chemical industry and high vapor pressure of volatile organic compounds (VOCs) have been caused that these materials recently be considered as a source of air pollution. These are different methods for separation of VOC from air that absorption by suitable and selective solvent is an efficient method. In this research, mathematical modeling of a packed absorption tower for separation of VOCs from air has been presented. Then, acetone vapors separation in this tower and with Intalox saddle packing has been investigated. Concentration of acetone in inlet air stream was 1.5 mol % which has reduced to 150 ppm (0.015 mol %) in effluent air stream. The results show that the packed absorption tower with this type of packing can separate 99% of acetone vapors. Comparison of the results obtained by Intalox saddle packing with the results obtained by another type of packing (with trade mark of Kerapak patented by Sulzer Company) shows that the tower gives the same efficiency for acetone separation. Thus, the efficiency of absorption process, mainly, depends on solvent type, composition of VOC in feed air, desired composition of VOC in outlet air (or percentage of VOC separation) and pressure drop. 相似文献
999.
Seasonal records of climatic change in annually laminated tufas: short review and future prospects 总被引:3,自引:0,他引:3
Many Recent and fossil freshwater tufa stromatolites contain millimetre‐scale, alternating laminae of dense micrite and more porous or sparry crystalline calcites. These alternating laminae have been interpreted to represent seasonally controlled differences in the biotic activity of microbes, and/or seasonally controlled changes in the rate of calcification. Either way, couplets of these microbially mediated alternating calcified laminae are generally agreed to represent annual seasonality. Combined stable isotope (δ18O and δ13C) and trace element (Mg, Sr, Ba) geochemistry from Recent tufa stromatolites show that seasonal climatic information is available from these calcites. Variability in δ18O (and in one case Mg concentration) has been shown to be controlled primarily by stream temperature change, usually driven by solar insolation. In arid climates, seasonal evaporation can also cause δ18O enrichment by at least 1‰. Variability in δ13C results potentially from: (1) seasonal change in plant uptake of 12C‐enriched CO2; (2) seasonal change in degassing of 12C‐enriched CO2 in the aquifer system; and (3) precipitation of calcite along the aquifer or river flow path, a process that increases δ13C of dissolved inorganic carbon (DIC) in the remaining water. Mechanisms 2 and 3 are linked because calcite precipitates in aquifers where degassing occurs, e.g. air pockets. The latter mechanism for δ13C enrichment has also been shown to cause sympathetic variation between trace element/Ca ratios and δ13C because trace elements with partition coefficients much greater than 1 (e.g. Sr, Ba) remain preferentially in solution. Since degassing in air pockets will be enhanced during decreased recharge when water saturation of the aquifer is lowest, sympathetic variation in trace element/Ca ratios and δ13C is a possible index of recharge and therefore precipitation intensity. High‐resolution geochemical data from well‐dated tufa stromatolites have great potential for Quaternary palaeoclimate reconstructions, possibly allowing recovery of annual seasonal climatic information including water temperature variation and change in rainfall intensity. However, careful consideration of diagenetic effects, particularly aggrading neomorphism, needs to be the next step. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
1000.
The conventional interpretation methods of pressuremeter testing effectively approximate pressuremeter membranes as infinitely long. As a result, the effects of the two‐dimensional geometry of pressuremeters are ignored, leading to an overestimation of soil shear strength by pressuremeter testing, as demonstrated in several previous studies. This paper presents results of a numerical study of two‐dimensional geometry effects on self‐boring pressuremeter tests in undrained clay. The results are obtained using critical state soil models with an effective stress formulation. This is in contrast to most (if not all) existing studies on pressuremeter geometry effects, which were based on perfectly plastic soil models (e.g. Yu (Cavity expansion theory and its application to the analysis of pressuremeters. DPhil Thesis, The University of Oxford, 1990), Yeung and Carter (Proc. 3rd Int. Symp. on Pressuremeters, 1990), and Houlsby and Carter (Géotechnique, 1993; 43 (4):567–576)). The present study suggests that the overestimation of soil strength due to the neglect of finite pressuremeter length is significantly affected by the soil model used in the calculations. It is found that for clays with a high overconsolidation ratio (OCR) the strength overestimation predicted using critical state soil models could be considerably smaller than that predicted using perfectly plastic soil models. The main conclusion of this numerical study is that care must be exercised before directly applying any numerically determined pressuremeter geometry correction factors in practice. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献