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221.
Stacin Martin Chen Zhu Joseph Rule Robert Ford Yee Soong 《Geochimica et cosmochimica acta》2005,69(6):1543-1553
Experiments of Zn2+ and Fe3+ coprecipitation as a function of pH were conducted in the laboratory at ambient temperature and pressure. X-ray diffraction patterns of the coprecipitates show two broad peaks at 0.149 and 0.258 nm, which is consistent with published patterns for pure 2-line ferrihydrite. Zn2+ uptake occurred at pH ≥5 while Fe3+ precipitation occurred between pH 3 and 4, although both Zn2+ and Fe3+ were present in the same solution during the entire range of pH titration. High-resolution transmission electron microscopy shows that the coprecipitates are 2 to 6 nm sized single crystalline particles but aggregated to 50 to 400 nm sized clusters. Analytical electron microscopy indicated that the 5% atomic Zn with respect to Fe was homogeneously distributed. No segregated phases were found in the clusters or at single crystal edges, which is consistent with published extended X-ray absorption fine structure (EXAFS) results at similar Zn/(Zn + Fe) ratios. Hence, occlusion and surface precipitation may be excluded as possible coprecipitation mechanisms. The bulk solution Zn2+ sorption edge was fitted to both solid solution and generalized diffuse layer surface complexation models. However, a solid solution model is inconsistent with published EXAFS results that show tetrahedral polydentate Zn2+ complexes sharing apices with Fe3+octahedra. 相似文献
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Spatial information on soil properties is an important input to hydrological models. In current hydrological modelling practices, soil property information is often derived from soil category maps by the linking method in which a representative soil property value is linked to each soil polygon. Limited by the area‐class nature of soil category maps, the derived soil property variation is discontinuous and less detailed than high resolution digital terrain or remote sensing data. This research proposed dmSoil, a data‐mining‐based approach to derive continuous and spatially detailed soil property information from soil category maps. First, the soil–environment relationships are extracted through data mining of a soil map. The similarity of the soil at each location to different soil types in the soil map is then estimated using the mined relationships. Prediction of soil property values at each location is made by combining the similarities of the soil at that location to different soil types and the representative soil property values of these soil types. The new approach was applied in the Raffelson Watershed and Pleasant Valley in the Driftless Area of Wisconsin, United States to map soil A horizon texture (in both areas) and depth to soil C horizon (in Pleasant Valley). The property maps from the dmSoil approach capture the spatial gradation and details of soil properties better than those from the linking method. The new approach also shows consistent accuracy improvement at validation points. In addition to the improved performances, the inputs for the dmSoil approach are easy to prepare, and the approach itself is simple to deploy. It provides an effective way to derive better soil property information from soil category maps for hydrological modelling. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Numerical simulation on mining-induced water inrushes related to geologic structures using a damage-based hydromechanical model 总被引:2,自引:1,他引:1
A large number of statistics indicate that water inrush has a direct relationship with geological structures such as fault
and karst collapse columns. Understanding the mechanism of water inrushes controlled by geologic structures is of vital importance
for adopting effective measures to prevent their occurrence. The work begins with formulization of a damage-based hydromechanical
model based on elastic damage theory. Next, the model is numerically implemented with finite element method by employing a
finite element package called COMSOL Multiphysics, and is also validated against some existing experimental observations.
Finally, the model is used to simulate the mining-induced groundwater inrushes when the effect of faults and karst collapse
columns is considered in the numerical simulation, and some suggestive conclusions for preventing water inrushes and optimizing
underground mining operations are drawn. 相似文献
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