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Vertical distribution of rare earth elements in a wetland soil core from the Sanjiang Plain in China

Journal of Rare Earths 2012年第7期30卷 731-738页

作者：程红光郝芳华欧阳威刘少卿林春野杨文静 State Key Joint Laboratory of Environmental Simulationand Pollution Control School of EnvironmentBeijing Normal University

The objective of this study was to investigate the vertical distribution of rare earth elements （REEs） in a natural wetland soil core to understand the influence of natural and anthropogenic activities on geochemical behavior of REEs. A natural wetland soil core of 95 cm was collected from the Sanjiang Plain in China and sliced into 5 cm slices for analyses of REEs, Fe, Al, Mn, Sc, Y, and soil organic matter （SOM）. Results indicated that SOM was accumulated in the upper part of the soil core （0 to 20 cm depth）, while Fe and Mn was reductively leached from the upper part of the soil core and accumulated in the low part. The content of total REEs ranged from 137.9 to 225.9 mg/kg in the soil core. Content profiles obtained for all REEs were almost identical except for Ce. The highest contents of REEs generally occurred at about 20 cm depth, but enrichment factor （EF） of REEs except Ce was usually the highest in the surface horizon. Average EF ranged from 1.1 for La to 2.1 for Gd. The pronounced shift in EF occurred at about 40 cm depth and it gradually increased from 40 cm depth to surface （except for Ce）, probably suggesting anthropogenic atmospheric deposition of REEs. In comparison with chondrite, Eu was depleted in all horizons, while Ce was negatively anomalous in the top horizons and positively anomalous in the bottom horizons. This positive anomaly of Ce in the bottom horizons was due to its preferential adsorption on Fe and Mn oxides, relative to other REEs. Although both natural and anthropogenic activi-ties influence the geochemical behaviors of REEs in soils, enrichment or mobility of REEs is low in the natural wetland soil core of the San-jiang Plain.

关键词： wetland soil core rare earth element distribution enrichment factor

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A Comparison of Five Different Techniques to Determine Hydraulic Conductivity of a Riparian soil in North Bavaria, Germany

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Pedosphere 2018年第3期28卷 443-450页

作者： Edzard HANGEN Friedhelm VIETEN Department of Preventive soil Protection and soil Monitoring Bavarian Environment Agency

soil saturated hydraulic conductivity(K_s) is a predominant input factor when forecasting the vertical transport of contaminants through the soil or when estimating the flood retention capacity of the soil. Displacement of contaminants in the soil over extended periods of time can be attributed mainly to matrix flow, whereas flow through macropores becomes significant under untypically wet conditions, e.g., during spills or rain storms. To obtain matrix conductivities for a soil, the effects of macropores should be ***, the K_s values of a soil profile are unlikely to be reflected solely by pedotransfer tables based on soil texture and bulk *** this study, we examined five different methods(pedotransfer table, soil core, borehole permeameter, particle-size distribution curve, and instantaneous profile) to determine K_s values for a mercury-contaminated riparian soil for subsequent simulation of longterm mercury displacement toward groundwater. We found that the determined K_s values increased in the following order: borehole permeameter soil core. The instantaneous profile method yielded K_s values of matrix flow, which additionally reflected the structure-related features of K_s values as provided by the soil core method. Despite being labor intensive and requiring expensive field sensors, the instantaneous profile method may provide the best representative in-situ K_s values for the studied site.

关键词： borehole permeameter contaminant transport Gleysol instantaneous profile method particle-size distribution curve pedotransfer table soil core

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The behavior of a rectangular closed diaphragm wall when used as a bridge foundation

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Frontiers of Structural and Civil Engineering 2012年第4期6卷 398-420页

作者： Qiangong CHENG Jiujiang WU Zhang SONG Hua WEN Department of Geological Engineering Southwest Jiaotong UniversityChengdu 610031China

The rectangular closed diaphragm(RCD)wall is a new type of bridge *** to barrette foundation,measuring the performance of RCD walls is relatively complicated because of their incorporation of a soil *** the FLAC3D software,this paper investigates the deformation properties,soil resistance and skin friction of a laterally loaded RCD wall as well as the settlement,axial force and load-sharing ratio of a vertically loaded RCD *** attention is given to the analysis of factors that influence the performance of the soil *** was found that under lateral loading,the RCD wall behaves as an end-bearing friction wall during the entire loading *** relative displacement between the wall body and the soil core primarily occurs below the rotation point,and the horizontal displacement of the soil core is greater than that of the wall *** vertical loading,the degree of inner skin friction around the bottom of the soil core and the proportion of the loading supported by the soil core increase with increased cross-section *** wall depth is directly proportional to the loading supported by the outer skin friction and the tip resistance of the wall body and is inversely proportional to the loading borne by the soil core.

关键词： diaphragm wall soil core bridge foundation FLAC3D bearing behavior

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