Surface and subsurface sedimentary structures produced by salt crusts

The growth and subsequent dissolution of salts on or within sediment may alter sedimentary structures and textures to such an extent that it is difficult to identify the depositional origin of that sediment and, as a result, the sediment may be misinterpreted. To help to overcome such problems with investigating ancient successions, results are presented from a comprehensive study of the morphology and fabrics of three large areas of modern salt flats in SE Arabia: the Sabkhat Matti inland region and the At Taf coastal region, both in the Emirate of Abu Dhabi, and the Umm as Samim region in Oman. These salt flats are affected by tidal‐marine, alluvial and aeolian depositional processes and include both clastic‐ and carbonate‐dominated surficial sediments. The efflorescent and precipitated salt crusts in these areas can be grouped into two main types: thick crusts, with high relief (>10 cm) and a polygonal or blocky morphology; or thin crusts, with low relief (<10 cm) and a polygonal or blister‐like appearance. The thin crusts may assume the surface morphology of underlying features, such as ripples or biogenic mats. A variety of small‐scale textures were observed: pustular growths, hair‐like spikes and irregular wrinkles. Evolution of these crusts over time results in a variety of distinctive sedimentary fabrics produced by salt‐growth sediment deformation, salt‐solution sediment collapse, sediment aggradation and compound mixtures of these processes. Salt‐crust processes produce features that may be confused with aeolian adhesion structures. An example from the Lower Triassic Ormskirk Sandstone Formation of the Irish Sea Basin demonstrates how this knowledge of modern environments improves the interpretation of the rock record. A distinctive wavy‐laminated facies in this formation had previously been interpreted as the product of fluvial sheetfloods modified by soft‐sediment deformation and bioturbation. Close inspection of laminations seen in core reveals many of the same sedimentary fabrics seen in SE Arabia associated with salt crusts. This facies is the product of salt growth on aeolian sediment and is not of fluvial origin.     

厚结壳的形成条件及控制因素分析

当前对于大洋厚结壳的研究较少,而厚结壳是未来开发利用的重点,同时它记录的地质历史长,控制和影响结壳生长发育的各种因素必然能在厚结壳上充分体现出来。因此,开展厚结壳的形成条件及控制因素的研究,具有重要的理论与现实意义。文章利用GIS空间分析技术与地质统计方法,对厚结壳的定义、结壳厚度与水深、结壳厚度与基岩、结壳生长与构造活动、结壳厚度与沉积速率、结壳厚度与经纬度、结壳厚度与主成矿元素之间的关系进行了分析,结果表明,结壳的厚度变化受控于水深、基岩、构造活动、沉积速率、经纬度等因素,同时结壳厚度与主成矿元素之间存在明显的相关性。     

Black crusts on travertine: factors controlling development and stability

The travertine buildings of Budapest show extensive black crust formation, which is related to high concentration of atmospheric pollution and a continental climate. Laminar black crusts, framboidal black crusts and leached white surfaces are compared. Physical properties (Schmidt hammer rebound, Duroscope rebound), mineralogical composition and elemental composition are measured. Framboidal black crusts contain more than 50% of acicular gypsum. The crust surface displays idiomorphic rosette-like gypsum crystals with particulates, calcite and gypsum crystal aggregates. The sulphur isotopic composition of the black crusts pinpoints the involvement of rain and dust in crust formation. Thick framboidal black crust has the lowest strength while thin laminar black crust and white dissolved surfaces show minor decrease in surface strength compared to unaltered travertine. The crusts adhere to the travertine surface and rarely show mechanical decay forms that are typical features of porous limestone ashlars in Budapest.     

吉林南部震旦纪万隆组与八道江组之间风化壳的发现

以往地质学家认为吉林省南部震旦纪万隆组与上覆八道江组之间是整合接触。笔者经过野外考察和室内研究 ,认为二者应为风化壳不整合接触关系。化学分析显示 ,风化壳泥岩与下伏母岩白云质灰岩相比化学成分发生巨大变化 ,粘土化矿物元素 (SiO2 Al2 O3 )与CaO和LOI的淋失相反 ,从 13.5 7%增加到 5 5 .6 3% ,具明显的风化成土特征。化学蚀变系数 (CIA)和质量迁移系数分析给出了相同的结果 :CIA值达到了 39.4 3% ,Ca元素的质量迁移系数达到 - 0 .97,几乎全部淋失 ,表明化学风化作用明显。综合研究表明 ,该风化壳处于碳酸盐岩风化成土的第二阶段 ,即母岩中“不溶物”在风化过程中逐步堆积形成残积土的阶段 ,为二级层序界面     

高寒冻土区生物结皮对土壤理化属性的影响

生物结皮是高寒地区地被层的重要组分之一。其作为地表特殊的结构层,能够改变地表结构及土壤理化属性,从而影响冻土环境。迄今为止,关于青藏高原高寒生态系统中生物结皮对土壤理化属性的影响尚不清楚。以青藏高原高寒冻土区生物结皮为研究对象,初步研究了生物结皮的特征及其对土壤理化属性的影响。结果表明：生物结皮在高寒草甸退化过程中广泛发育,主要以藻结皮为主,其盖度可达37.3%~51.7%,结皮层平均厚度为12.6 mm。由于生物结皮的发育,高寒地区5~20 cm土层粉粒含量有所增加,但差异不显著,而结皮层土壤田间持水量相比于裸地表层（2 cm）增加了10%~40%,结皮层容重较裸地降低了30%;两种类型藻结皮均显著增加了结皮层及其下0~20 cm土层土壤有机质,而深色藻结皮增加了结皮层及其下0~20 cm土层土壤全氮含量,浅色藻结皮仅增加了结皮层土壤全氮含量,对其下0~20 cm土层土壤全氮含量没有显著影响;生物结皮对土壤pH没有显著影响;生物结皮是高寒生态系统植被退化过程中的关键环节。研究结果为揭示生物结皮在高寒生态系统中发挥重要生态功能提供依据。     

Variation of albedo to soil moisture for sand dunes and biological soil crusts in arid desert ecosystems

Surface albedo plays a crucial role in the energy balance of soils. The surface albedo and surface soil moisture of bare sand and biological soil crusts (BSCs) were concurrently observed on field plots of shifting sand dune and in revegetated desert ecosystems at Shapotou, northwestern China, to study relationships between surface albedo, solar elevation angle, and surface soil moisture. Results indicated that rainfall exerted a remarkable lowering effect on the variation of surface albedo by increasing surface soil moisture. Surface albedo was an exponential function of solar elevation angle, and the normalized surface albedo (solar elevation angle effect was removed) decreased exponentially with the increase of surface soil moisture. Sand surface had a higher albedo (0.266) than BSCs (0.226) when the surfaces were very dry. However, sand surface albedo became increasingly lower than that of BSCs when the surfaces were in wet conditions and when the soil moisture exceeded a critical value. The changes in soil surface albedo from sand dune to BSCs after revegetation in shallow soil profiles associated with the variation of the surface soil moisture can be seen as an indicator of the degree of sand dune stabilization when compared with the original shifting sand dune soil.     

Elisional processes and salt tectonics: Communication 2. Formation mechanism of salt diapirs

The possible role of endogenic factors in the formation of salt deposits and salt diapirs is discussed with emphasis on the sedimentary origin of salts and elisional nature of epigenetic salt bodies. It is shown that dehydration and high solubility of chlorides, density inversion, and high coefficient of linear expansion under heating are the main factors responsible for the growth of salt domes. Elisional processes in clays of subsalt formations exert a considerable impact upon their growth in rock basins. Tectonic processes play an important, although secondary, role in these transformations.     

土层结构对非饱和毛细水盐运移的影响

层状土层之间孔隙结构和水力学性质的不连续性对土体水盐运移有显著影响。基于现场调查,设计了两种不同粒径土层二元结构组合（黄土-砂质粉土和黄土-粉质黏土）的室内土柱试验,通过模型试验讨论了不同地下水补给条件下土层结构对毛细水分布和盐分累积的影响。试验结果表明：在毛细水补给条件下,黄土-砂质粉土构成的上细下粗型土层结构有利于毛细水盐运移,经过60 d蒸发后,其表层${\rm{SO}}_{\rm{4}}^{{\rm{2 - }}}$含量是上粗下细型土柱的两倍。在无毛细水补给条件下,砂质粉土层中水盐向上迁移总量和迁移速率大于粉质黏土层,最终上细下粗型土柱中上覆土层各层位离子含量均大于上粗下细型土柱。研究结果为层状土区盐渍土病害的防治提供了试验参考。     

Potentials of the microalgae inoculant in restoration of biological soil crusts to combat desertification

The world is presently faced to the many calamities, mainly the increased and rapidly developing environmental changes, soil degradation as an example of such environmental problems which is correlated with the destructive effects of the sandstorms. Biological soil crust (BSC), a main component of soil, has various environmental functions including reduction in the erosion by increasing soil stability and providing a sanctuary for the growth of the taxa and vascular plants communities. Destruction of BSC, which naturally can be recovered slowly in a long time processes, contributes to the desertification and other environmental catastrophes. Therefore, accelerating the BSC recovery both the quality and the quantity of the crust development, especially in the desert areas, is of the prime interest. Recent advances in the BSC restoration have provided an immense potential for emulating the natural restoration methods mainly through providing soils with inoculant. This paper reviews the present restoration-based procedures for the biological soil crust restoration practice. The main landmarks are presented and highlighted including strain(s) selection and development, mass biomass production, inoculum preparation, soil inoculation, soil augmentation, nurseries, and crust succession monitoring and control. The review also introduces several successful case studies in the USA and the Republic of China. Thereafter, the paper briefly documents the future directions of the research and technologies. Development of a restoration system through the application of the microalgae inoculant is an encouraging aspect for accelerating the BSC recovery of the arid and semi-arid areas. However, further researches will help to establish and consolidate the potential of the microalgae cells and their application in desertification programs in large scales and in accordance with principles and requirements mandated by economic standards.     

Biogenic soil crusts and soil depth: a long‐term case study from the Central Negev desert highland

Wind‐blown soil degradation is a major problem in arid regions. Biogenic soil crust consists of a dense growth of many small organisms covering bare desert soil surfaces in arid regions worldwide. These organisms perform essential services in the ecosystem, for example, soil surface stabilization and carbon and nitrogen fixation. A unique service provided by biogenic crusts is the incorporation of large quantities of deposited atmospheric particles, leading to a significantly enhanced rate of increase in soil depth in windy and arid environments. A long‐term study (over 42 months) was conducted to investigate the contribution of a biogenic crust to the accumulation of atmospheric particles in an arid zone. Undisturbed and treated biogenic crusts were studied for their capacity to incorporate deposited particles. Atmospheric particles were found to accumulate on marble dust collectors at a rate of 120 g m^?2 year^?1 and on sterilized crust at a rate of 208 g m^?2 year^?1, while the accumulation rate on live, intact crusts was 277 g m^?2 year^?1, suggesting a soil depth accretion rate on an undisturbed biogenic crust of 10 mm every 33 years. Maintenance of a healthy biogenic crust in dry land environments should, therefore, be a major consideration for improving soil quality and increasing soil depth in arid regions.     

Discussion on the development of salt chemical industry chain

正China Pingmei Shenma Group is a large enterprise based on energy and chemical,with an annual output of 70million tons of coal,16 million tons of coke,680,000 tons of caustic soda,450,000 tons of PVC resin,50,000 tons of     

钾盐和磷酸盐对固化土早期强度的影响研究

利用土壤板结原理,通过对硫铝酸盐水泥固化土无侧限抗压强度试验和水稳定性试验,探讨钾盐、磷酸盐对其早期强度的影响规律;通过X射线衍射（XRD）对固化土的物相成分进行了分析,探讨钾盐、磷酸盐影响固化土强度的变化内在机制。试验结果表明,钾盐、磷酸盐对固化土强度提高的阈值为0.6%,当盐掺入量低于该阈值时,固化土强度会随着盐掺量的增加而提高,当盐掺入量超过该阈值时,固化土强度会逐渐降低。盐掺入量不超过2%时,掺盐固化土水稳定性与未掺盐固化土差不多,7 d固化土软化系数基本保持在70%以上,但掺入K2SO4的固化土水稳定性较差,软化系数在60%左右。生成高强难溶具有膨胀性的矿物晶体是掺盐固化土早期强度提高的主要原因,但盐掺入量过高,固化土中矿物晶体过多膨胀作用,破坏固化土结构,而使固化土早期强度降低。     

Successional stages of biological soil crusts and their microstructure variability in Shapotou region (China)

In order to investigate succession of biological soil crusts (BSCs) and their microstructure variability, we conducted this work in Shapotou revegetation region at the southeast edge of Tengger Deser. The results showed that BSCs generally succeeded as a pathway of “Algae crusts, algae–lichen crusts, lichen crusts, lichen–moss crusts and moss crusts”. Occasionally mosses directly occurred on algae crusts, and BSCs succeeded from algae crusts to moss crusts. Crust vertical stratification was a common phenomenon, from top to bottom an inorganic layer, algae-dense layer and algae-sparse layer were divided in algae crusts; a thallus layer, rhizoid layer and sub-rhizoid layer in lichen crusts; a “stem-leaf” layer, rhizoid layer and sub-rhizoid layer in moss crusts, respectively. The main crust binding organisms varied from filamental cyanobacteria (dominated by Microcoleus) in algae crusts to lichen rhizoids, free-living cyanobacterial filaments and fungal hyphaes in lichen crusts, and to moss rhizoids and fungal hyphaes in moss crusts. The dominant phototrophic organisms varied from Microcoleus (algae) in algae crusts to Collema (lichens) in lichen crusts, and to Bryum (or Didymodon and Tortula; mosses) in moss crusts. Total phototrophic biomass increased while the free-living algal biomass decreased with the succession of BSCs. In addition, exopolysaccharides and fine particles accumulated in the course of development and succession of BSCs, all of which lead to a gradual increase in crust thickness and porosity, while decrease in the bulk density.     

膜下滴灌微区环境对土壤水盐运移的影响

基于膜下滴灌特有的"膜中"、"膜间"、"膜边"、"膜外"微区环境,利用2011—2013年田间对比试验方法获取的5 960个数据,运用柯布-道格拉斯模型,构建膜下滴灌环境土壤层次、灌水定额、土壤水分、气温、蒸发综合因素与土壤水盐关系及影响效应分析模型.结果表明,在气候干旱、蒸发强烈灌区,地膜覆盖与滴灌结合的地表介面灌溉形式下,土壤水盐具有水平方向由"膜中"向"膜边"地表裸露区定向迁移,垂直方向土壤水盐则由下向上层运移且趋于"膜外"边界积累的趋势,尤其是气温与蒸发因素交互作用,推进膜下滴灌土壤水盐在地膜覆盖与土壤裸露区域空间运移,研究结果进一步揭示了膜下滴灌"土壤水盐定向迁移"形成机理,为膜下滴灌土壤水盐地表排放模式应用提供了依据.     

Prediction of the speciation of alkaline earths adsorbed on mineral surfaces in salt solutions

Despite the fact that the bulk compositions of most low temperature natural surface waters, groundwaters, and porewaters are heavily influenced by alkaline earths, an understanding of the development of proton surface charge in the presence of alkaline earth adsorption on the surfaces of minerals is lacking. In particular, models of speciation at the mineral-water interface in systems involving alkaline earths need to be established for a range of different minerals. In the present study, X-ray standing wave results for Sr²⁺ adsorption on rutile as a tetranuclear complex [Fenter, P., Cheng, L., Rihs, S., Machesky, M., Bedyzk, M.D., Sturchio, N.C., 2000. Electrical double-layer structure at the rutile-water interface as observed in situ with small-period X-ray standing waves. J. Colloid Interface Sci.225, 154-165] are used as constraints for all the alkaline earths in surface complexation simulations of proton surface charge, metal adsorption, and electrokinetic experiments referring to wide ranges of pH, ionic strength, surface coverage, and type of oxide. The tetranuclear reaction

4>SOH+M²⁺+H₂O=(>SOH)₂(>SO^-)₂_M(OH)⁺+3H⁺     

Formation of hydroxyl radicals catalyzed by clay surfaces

 The formation of superoxide and hydroxyl radicals at the surface of smectite clays due to oxygen reduction is demonstrated by electron paramagnetic resonance spectroscopy. The yield of hydroxyl radicals is mainly a function of particle size of the clays and depends, to a lesser extent, on the clay lattice iron. Synthetic laponite clay with small platelet size (∼20 nm) and without lattice iron is leading in the formation of hydroxyl radicals followed by montmorillonite (∼200 nm). Fluorohectorite (∼2000 nm) was inactive to hydroxyl radical formation by oxygen reduction. Received: 20 January 2001 / Accepted: 7 August 2001     

农田水盐调控现实与面临问题

农田土壤盐碱化是农业可持续发展的主要威胁之一,为创建适应现代生态农业发展的农田水盐调控方法,在总结农田盐分来源及其累积动力特征的基础上,从土壤盐分影响土壤供养能力和作物生产能力两大方面,分析土壤盐分对土壤-作物系统功能的影响途径,明确农田水盐高效调控方向。根据不同时代的治盐理念,将水盐调控发展历程分成4个阶段,以抑制盐碱胁迫对土壤和作物的危害为切入点,解析水利措施、化学措施、生物措施和农艺措施的作用特点和调控目标及适用范围。根据现代农业绿色发展与提质增效需求,凝练盐碱胁迫农田控害增效水盐调控理念,提出水盐调控策略,即调控根际水盐传输动力特征,重构农田水盐分布空间格局,提升农业改土促生措施功效;指出农田控害增效水盐调控急需解决的关键技术,总结了创新水盐调控理论有待深入研究的基础科学问题,以期为盐碱胁迫农田绿色、高效和可持续利用提供指导。