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21.
Daoyong ZHANG Xiangliang PAN Shuimu LIAO Chenglin HUANG Jingmei ZHANG 《中国地球化学学报》2006,25(B08):133-133
Low molecular weight organic acids (LMWOAs) are important components of root exudates. They play an important role in immobilizing and remobilizing contaminants in rhizospheric soil. Effects of four LMWOAs on the sorption and desorption behavior of p-chlorophenol by yellow earth was studied in batch mode. The results showed that the previous application of LMWOAs to enhanced adsorption capacity of p-chlorophenol of the soil in the order of maleic acid〉malic acid〉oxalic acid〉citric acid. However, when LMWOAs were applied to soil where p-chlorophenol had been previously adsorbed, substantial p-chlorophenol was desorbed from soil by oxalic acid, whereas citric acid, malic acid and maleic acid didn't desorb as much p-chlorophenol from soil as deionized water. 相似文献
22.
Porphyroblast rotation during crenulation cleavage development: an example from the aureole of the Mooselookmeguntic pluton, Maine, USA 总被引:1,自引:0,他引:1
In the low‐pressure, high‐temperature metamorphic rocks of western Maine, USA, staurolite porphyroblasts grew at c. 400 Ma, very late during the regional orogenesis. These porphyroblasts, which preserve straight inclusion trails with small thin‐section‐scale variation in pitch, were subsequently involved in the strain and metamorphic aureole of the c. 370 Ma Mooselookmeguntic pluton. The aureole shows a progressive fabric intensity gradient from effectively zero emplacement‐related deformation at the outer edge of the aureole ~2900 m (map distance) from the pluton margin to the development of a pervasive emplacement‐related foliation adjacent to the pluton. The development of this pervasive foliation spanned all stages of crenulation cleavage development, which are preserved at different distances from the pluton. The spread of inclusion‐trail pitches in the staurolite porphyroblasts, as measured in two‐dimensional (2‐D) thin sections, increases nonlinearly from ~16° to 75° with increasing strain in the aureole. These data provide clear evidence for rotation of the staurolite porphyroblasts relative to one another and to the developing crenulation cleavage. The data spread is qualitatively modelled for both pure and simple shear, and both solutions match the data reasonably well. The spread of inclusion‐trail orientations (40–75°) in the moderately to highly strained rocks is similar to the spread reported in several previous studies. We consider it likely that the sample‐scale spread in these previous studies is also the result of porphyroblast rotation relative to one another. However, the average inclusion‐trail orientation for a single sample may, in at least some instances, reflect the original orientation of the overgrown foliation. 相似文献
23.
Integrated, in situ textural, chemical and electron microprobe age analysis of monazite grains in a migmatitic metapelitic gneiss from the western Musgrave Block, central Australia has identified evidence for multiple events of growth and recrystallisation during poly-metamorphism in the Mesoproterozoic. Garnet + sillimanite-bearing metapelite underwent partial melting and segregation to palaeosome and leucosome during metamorphism between 1330 and 1296 Ma, with monazite grains in leucosome recording crystallisation at 1300 Ma. Monazite breakdown during melting is inferred to have occurred in the palaeosome. During a subsequent granulite facies event at 1200 Ma, deformation and metamorphism of leucosome and palaeosome resulted in partial disturbance of ages and potential minor growth on 1300 Ma monazite in leucosome. Growth of new, high-Y (+HREE) monazite in palaeosome domains occurred during garnet breakdown in the presence of sillimanite to cordierite and spinel, as a result of post-peak isothermal decompression. Diffusive enrichment of resorbed garnet rims in Y + HREE suggests garnet breakdown occurred slower than volume diffusion of REE. Monazite in both palaeosome and leucosome were subsequently partially to penetratively recrystallised during a retrogression event that is suggested to have occurred at 1150–1130 Ma. The intensity of recrystallisation and disturbance of ages appears linked to proximity to retrogressed garnet porphyroblasts and their occurrence in the relatively reactive or ‘fertile’ local environments provided by the palaeosome/mesosome volumes, which caused localised changes in retrogressive fluids towards compositions more aggressive to monazite. Like reaction textures, it is apparent that domainal equilibrium and reaction may control or at least strongly influence monazite REE and U–Th–Pb chemistry and hence ages. 相似文献
24.
To estimate static and seismic active earth pressure (Pad) on a rigid retaining wall, numerical analyses using different step sizes have been carried out in this paper, based on the
modified Culmann line method by considering Coulomb’s planar rupture surface. Equivalent pseudo-static seismic forces are
considered in the analysis. A new concept of modified unit weight by considering ground surcharge is introduced under static
and seismic conditions. By numerical analysis, area of soil (A) has been estimated to obtain the ratio of A/A0 where A0 is θh2, θ is the angle between retaining structure and ground surface and h is the vertical height of the wall. This ratio remains constant for a particular type of soil and has been used to estimate
the maximum active earth pressure using force diagram. Results are provided in tabular form for easy calculation of the coefficient
of static and seismic active earth pressure. Present results by considering the new technique, compares well with the results
obtained by earlier researchers. 相似文献
25.
大气CO2浓度升高对土壤中不同粒级碳的影响 总被引:4,自引:0,他引:4
不同粒级土壤中的碳有着不同的周转规律,在高CO2浓度条件下,它们含量的变化将在一定程度上反映土壤碳是累积还是减少,对明确土壤碳的变化趋势有重要意义.采用田间培养试验初步模拟研究在高CO2浓度条件下土壤不同粒级碳的分布.结果表明,加入秸秆培养1年,由于CO2浓度升高的原因导致在低氮(LN)、常规氮(NN)和高氮(HN)水平下土壤中碳分别增加0.01、1.10、1.22g/kg,表现为粒级〈53μm土壤颗粒中碳分别增加1.53、2.19、2.70g/kg.粒级〈53μmm土壤颗粒碳量的增加,主要是由于其重量分配百分数显著增加36.2%,碳浓度增加5.4%;粒级〉250μm和250~53μm土壤颗粒部分虽然其碳浓度分别增加20.8%和17.3%(P〈0.05),怛由于重量分配百分数分别显著降低22.8%和36.1%,结果碳量降低.试验表明高CO2浓度导致不同粒级土壤的分配及碳浓度的变化;高氮施肥水平下有增加土壤碳量特别是小粒级土壤碳量的趋势. 相似文献
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28.
华南地区晚二叠和晚三叠世煤中稀土元素特征研究 总被引:2,自引:0,他引:2
在华南地区贵州六盘水、江西乐平、露庆和湖北黄石矿区晚二叠和晚三叠世煤层的稀土元素ICP—MS分析数据的基础上,系统研究了研究区煤中稀土元素的含萤分布特征、赋存特征、配分模式以及地质控制因素。含量分布表明晚二叠世稀土元素含量总体高于晚三叠世;煤中稀土元素与灰分成正相关关系,部分煤样品由于有富稀土元素的重矿物组合的存在而出现稀土元素的异常高值;同一矿区、同一时代煤中稀土元素的配分模式具有一定的相似性,而不同地区同一时代和同一地区不同时代煤中稀土元素的配分模式具有较大差异;煤的沉积环境,煤中无机矿物组成以及海水的影响是控制煤中稀土元素含量和配分模式的主要地质因素。 相似文献
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