塔克拉玛干沙漠优势植物化学成分特征   总被引：7，自引：0，他引：7  

夏阳 《中国沙漠》1994,14(2):30-36

塔克拉玛干沙漠优势植物化学成分的若干特征与土壤盐分的性质相联系，对优势植物及植物群落的化学元素特征型、盐生植物类群的划分进行了讨论。在塔克拉玛干沙漠环境中，藜科植物占有一定优势、且含有较高的可溶性盐分和灰分，而海蓬子、盐节木、盐穗木是一类富含Ｎａ和Ｃｌ的植物，芦苇、小獐毛是富含ＳｉＯ＿２的植物。  相似文献   

Rock block monitoring of rapid salt weathering in southern Tunisia     

A. S. Goudie  A. Watson 《地球表面变化过程与地形》1984,9(1):95-98

Rectangular blocks of York Stone and of concrete placed on a sodium chloride sabkha in southern Tunisia for six years suffered very severe breakdown, thereby indicating the power of salt weathering as a process in sabkha environments.  相似文献   

Micro area transportation of residues： A style forming the red weathering crusts of carbonate rocks     

Zhigang FENG Shijie WANG Xiuming LIU Weijun LUO Qingliang WANG 《中国地球化学学报》2006,25(B08):170-171

The red weathering crusts of carbonate rocks are usually characteristic of thick-bedded intensely weathered profiles and strongly undulate basement rock surface （i.e., alternative distribution of solution grooves and stone teeth）. In this work a typical red weathering crust of carbonate rock, whose parent rock is of homogeneity in composition, is selected in karst terrace, middle Guizhou Province, China. Via field geology, geochemistry, mineralogy, grain size analyses, and in comparison with two neighbouring limestone soils as well, the authors have discussed forming process of the red weathering crusts of carbonate rocks, and demonstrated that micro area transportation of acid-insoluble residues of carbonate rocks is a style of forming the red weathering crusts of carbonate rocks. The weathering front is a main place of geochemical reaction, and at this limited-thick interface, with quick dissolution of carbonates, acid-insoluble residues begin to obviously decompose.  相似文献   

Predicting Uniaxial Compressive Strength by Point Load Test: Significance of Cone Penetration   总被引：4，自引：0，他引：4  

A. Basu  A. Aydin 《Rock Mechanics and Rock Engineering》2006,39(5):483-490

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A change-detection application on the evolution of Kahak playa (South Khorasan province, Iran)     

Mohammad Hossein Rezaei Moghaddam  Mahdi Saghafi 《Environmental Geology》2006,51(4):565-579

Kahak salt playa in South Khorasan province of Iran, have special geomorphological characteristics by the presence of ephemeral saline lakes, wetlands, salt crusts, surface accumulations of salt and zones of patterned ground. Salt crusts in the soil surface are unique in the region and have laminated horizons in the playa soil. Soil-surface salt accumulations are dominated by NaCl and gypsum. It has been found that distribution of chemical soluble is not uniform across the playa landscape, and this result influences on the variety form of patterned ground. In this study, the percent changes in some of the chemical elements such as NaCl, gypsum and also brine extent have been calculated in the playa. Indicating changes in Kahak salt playa is the main aim of this study by using remote sensing and GIS techniques. In this paper, techniques such as spectral un-mixing, maximum likelihood classification, band rationing, fuzzy classification and correlation relationships are discussed. This contribution presents modeling of temporal and spatial changes of salinity and playa developing using combined approaches that incorporate different data-fusion and data-integration techniques for two periods of date. Furthermore, percent changes in the surface-patterned ground of the playa have been calculated using texture and pattern analysis of the PCA1. Results have revealed that, in the playa developing, chemical materials such as sodium, NaCl, gypsum and also brine extent are positively correlated with each other and the most increased changes are related to gypsum and the most decreased changes are related to the NaCl. Also changes in the amount of agricultural area in the playa-lakes margin, show low effects in the desertification process.  相似文献   

Geochemistry of Mansar Lake sediments, Jammu, India: Implication for source-area weathering, provenance, and tectonic setting   总被引：5，自引：0，他引：5  

Brijraj K. Das  A.S. AL-Mikhlafi  P. Kaur 《Journal of Asian Earth Sciences》2006,26(6):649-668

The sediment geochemistry, including REE, of surface and core samples from Mansar Lake, along with mineralogical investigations, have been carried out in order to understand the provenance, source area weathering, hydrolic sorting and tectonic setting of the basin. The geochemical signatures preserved in these sediments have been exploited as proxies in order to delineate these different parameters.The major element log values (Fe₂O₃/K₂O) vs (SiO₂/Al₂O₃) and (Na₂O/K₂O) vs (SiO₂/Al₂O₃) demarcate a lithology remarkably similar to that exposed in the catchment area. The chondrite normalized REE patterns of lake samples are similar to Post Archaean Australian Shale (PAAS) with LREE enrichment, a negative Eu anomaly and almost flat HREE pattern similar to a felsic and/or cratonic sedimentary source. However, the La–Th–Sc plot of samples fall in a mixed sedimentary domain, close to Upper Continental Crust (UCC) and PAAS, suggesting sedimentary source rocks for the Mansar detritus. It also indicates that these elements remained immobile during weathering and transportation. The mineralogical characteristic, REEs, and high field strength elements (HFSE), together with the high percentage of metamorphic rock fragments in the Siwalik sandstone, support a metamorphic source for lower Siwalik sediments. A very weak positive correlation between Zr and SiO₂, poor negative correlation with Al₂O₃, negative correlation of (La/Yb)_N and (Gd/Yb)_N ratios with SiO₂ and positive correlation with Al₂O₃, suggest that Zr does not dominantly control the REE distribution in Mansar sediments. The petrographic character and textural immaturity indicate a short distance transport for the detritus. The distribution of elements in core samples reflect fractionation. The higher Zr/Th and Zr/Yb ratios in coarse sediments and PAAS compared to finer grained detritus indicate sedimentary sorting. Plots of the geochemical data on tectonic discrimination diagrams suggest that the sediments derived from the lower Siwalik were originated within a cratonic interior and later deposited along a passive margin basinal setting. It therefore reveals lower Siwalik depositional history.  相似文献   

Rhizosphere: A new frontier for soil biogeochemistry   总被引：9，自引：0，他引：9  

Philippe Hinsinger  Claude Plassard  Benoît Jaillard 《Journal of Geochemical Exploration》2006,88(1-3):210

A range of key biological functions of plant roots such as uptake, respiration and exudation can considerably alter biogeochemical parameters of the soil in the vicinity of the roots, i.e., the rhizosphere: concentrations of nutrients, toxic elements (e.g., aluminium) and pollutants, concentrations of complexing or chelating compounds, pH and redox potential, partial pressures of gases such as O₂ and CO₂, etc. Such parameters can also be directly influenced by the activities of soil microorganisms that are known to be stimulated by root exudation in the rhizosphere. Changes of biogeochemical parameters of the soil solution occurring in the rhizosphere influence a whole range of reactions at the soil solid/soil solution interface. Higher plants thereby play a key role in (i) the weathering of soil minerals, (ii) soil formation processes (pedogenesis) and (iii) the biogeochemistry of elements that are either beneficial or toxic to themselves and other soil biota.  相似文献   

原生硅酸盐矿物风化产物的研究进展——以云母和长石为例   总被引：6，自引：0，他引：6  

李福春 李莎杨用钊  程良娟 《岩石矿物学杂志》2006,25(5):440-448

研究云母和长石等原生硅酸盐矿物的风化速率和风化产物对于深入理解土壤发生过程、营养元素循环以及全球气候变化具有重要的理论意义。本文从自然风化、人工化学风化和生物风化3方面总结了原生硅酸盐矿物风化作用及其产物的特点，重点阐述了微生物参与下的生物风化作用和生物矿化作用及其意义。野外观察和室内实验研究结果表明，微生物可以加速矿物的分解，而且其细胞表面及其产生的胞外多聚糖可以作为次生矿物成核的模板。  相似文献   

三亚活体珊瑚的微量元素与硼同位素组成的初步研究          下载免费PDF全文

李华玲  肖应凯  魏海珍  杜秀月  王秀芳  陈玉锋 《盐湖研究》2006,14(2):35-41

测定了三亚活体珊瑚和其生长海域海水的Ca、Mg、B、Sr含量和B同位素组成,结果表明珊瑚中这些元素的浓度与对应海水的相同元素呈现出弱的正或负相关性,所有的相关系数均不大于0.3,这表明珊瑚的这些化学成分主要不是由对应海水所决定。Ca,Sr和B在珊瑚中均得到富集,其中Sr的富集程度最高,达3.08×103,而Mg在珊瑚中却是贫化的。珊瑚中Sr的掺入对B的掺入的影响要高于主成分Ca本身的影响,δ11B值与珊瑚的主成分Ca的浓度几乎无关,而与B、Sr和Mg浓度分别具有较弱的正相关和负相关关系,相关系数分别为0.343,0.309和0.276,珊瑚Sr浓度的增加引起B浓度的增加,同时会引起δ11B值的增加,而Mg的影响与此相反。  相似文献   

Weathering Pits as Indicators of the Relative Age of Granite Surfaces in the Cairngorm Mountains, Scotland     

Adrian Malcom Hall  William Morton Phillips 《Geografiska Annaler: Series A, Physical Geography》2006,88(2):135-150

Weathering pits 1–140 cm deep occur on granite surfaces in the Cairngorms associated with a range of landforms, including tors, glacially exposed slabs, large erratics and blockfields. Pit depth is positively correlated with cosmogenic exposure age, and both measures show consistent relationships on individual rock landforms. Rates of pit deepening are non‐linear and a best fit is provided by the sigmoidal function D = b1 + exp(b2+b3/t). The deepest pits occur on unmodified tor summits, where ¹⁰Be exposure ages indicate that surfaces have been exposed to weathering for a minimum of 52–297 ka. Glacially exposed surfaces with pits 10–46 cm deep have given ¹⁰Be exposure durations of 21–79 ka, indicating exposure by glacial erosion before the last glacial cycle. The combination of cosmogenic exposure ages with weathering pit depths greatly extends the area over which inferences can be made regarding the ages of granite surfaces in the Cairngorms. Well‐developed weathering pits on glacially exposed surfaces in other granite areas are potential indicators of glacial erosion before the Last Glacial Maximum.  相似文献