On Biochemical Formation of Salt Deposits

A water/salt system in an evaporative environment is both a physicochemical region and a biological one. All the parameters of the system, such as the salinity, temperature and CO2 partial pressure, are affected by halo-philic bacteria. The system controls salt deposition but is modified by an accompanying ecological system; therefore it should be called a water/salt/biological system. Salt minerals result from accumulation of the remains of bacteria/algae, namely, bacteria/algae formation; whereas biological, biophysical and biochemical processes provide full evidence for organic involvement. Consequently, salt deposits should not be called purely chemical but biological/chemical ones. This new argument supplements and develops the traditional idea and helps perfect the mineralization theory of salts and even general deposits, thus giving guidance to prospecting for salt deposits.     

西北地区干旱化趋势及水盐失衡的生态环境效应

基于对西北地区干旱化趋势的讨论, 研究了西北内陆封闭盆地水盐迁移聚集的系统动力学模式, 阐明了盆地浅表积盐与水盐失衡的根本原因.在此基础上, 探讨了水盐分布与生态适宜性之间的内在联系以及水循环节律的变化对土壤生态指数时空分布的影响, 提出建立西北地区各物种的生存域及土壤生态指数对西部大开发具有重要意义.此外, 还讨论了内陆盆地水库工程兴建与灌溉技术选择问题      

论盐钾与油气的关系

盐钾与油气有着密切的共存关系。一个持续发展的封闭或半封闭沉降盆地 ,有利于盐钾和油气的形成 ,含盐含钾岩系对油藏能起到良好的封闭保护作用 ,且其变形对油气的运移也起到重要作用。国内外大量油气及岩盐钾盐的勘查实践也多次证实了二者之间存在着密切的关系 ,而且二者的勘查手段和方法一致。因此在油气勘查中兼找岩盐和钾盐 ,实施兼探 ,必将取得事半功倍的找矿效果 ,值得引起人们重视。     

石家庄市地下水盐污染评价——双权均值法

石家庄市地下水盐污染是区域地下水环境质量恶化的突出表现,其研究具有典型示范性。筛选确定盐污染因子（地下水硬度、总固溶物、Cl＾－、SO4＾2－、NO3＾－）,采用综合污染指数计算－－双权均值法进行地下水综合盐污染评价,方法简捷,是一种新的尝试。     

盐湖及相关资源开发利用进展(续完)

对近年来国内外盐湖资源开发利用的进展情况加以介绍 ,也涉及到国外钾、锂、镁、硼、碘等相关产品的生产、消费、价格等情况。还对资源开发的可持续发展以及我国盐湖及相关资源开发的某些问题加以讨论     

Invading cord grass vegetation changes analyzed from Landsat-TM imageries: a case study from the Wanggang area, Jiangsu coast, eastern China

Cord grass colonization on the Jiangsu coast, eastern China, modifies the native salt marshes in terms of ecosystem structure. The Landsat TM images from 1992 to 2003 were analyzed to identify salt-marsh vegetation distribution patterns and their changes over this coastal region, in order to evaluate the effects of the spreading of the artificially introduced halophyte Spartina. Supervised classification was performed using Bands 3, 4 and 5 in conjunction with in situ training samples, to derive the distribution pattern of the vegetation in the study area. Further, in order to identify the intertidal areas with different tidal elevations, a data treatment procedure was designed to combine regional water level data using harmonic analysis with the waterlines on the TM images extracted by density slice. The results show that: (1) the Spartina alterniflora area has been expanding towards the sea rapidly since it was introduced, especially at initial stages; (2) in the upper part of the inter-tidal zone, the local marsh plant Suaeda salsa and the exotic species Spartina anglica were present only near the sea dyke, occupying only a small part of the entire salt marsh, and the area of these two species has been reduced by land reclamation; (3) there has been a trend for Spartina alterniflora to become the dominant species in the salt marshes in the study area; and (4) the elevation of Spartina alterniflora’s seaward fringe was close to mean high water on neaps, and its landward boundary was slightly higher than mean high water. The salt marsh environment of the study area has been modified rapidly by the Spartina vegetation for the last 12 years.     

含水介质中粘粒释放的临界盐浓度测定

通过渗流试验和批量试验,对多孔介质水敏感性发生过程中颗粒释放的临界盐浓度进行了测定.试验结果表明:水动力条件也能导致颗粒释放的发生,但是释放量很小;当 NaCl 溶液浓度达到0.06mol/L 左右时,开始发生明显的颗粒释放现象,而其临界盐浓度并非是个单一值,可以确定为一个范围,即(0.06±0.005) mol/L;当NaCl溶液浓度为0.03mol/L时,颗粒释放量最大.     

Patterns of unsuccessful shell-crushing predation along a tidal gradient in two geographically separated salt marshes

Gradients in salt marsh ecosystems that result from reduced tidal inundation time in the high marsh offer an opportunity to assess the importance of predation as a selective agent (indexed by the time-averaged record of unsuccessful predation, which integrates potentially confounding short-term – inter-seasonal and inter-annual – fluctuations in predation pressure). Spatial patterns in selection pressure are expected to decrease landward from the seaward edge of the marsh. Interaction between shell-breaking predators and their snail prey, Littoraria irrorata, however, generated a pattern in the frequency of sublethal injury (shell repair), standardized for snail size, that did not follow this simple, single-variable prediction of decreasing repair frequencies with distance from the seaward edge of the marsh, based on inundation time alone. Patterns of repair frequency increased landward from the seaward edge of the marsh, only declining as predicted after a zone of dense stands of salt marsh grass. The interaction of tidal inundation time and primary habitat structure ( e.g. physical vegetative barriers to dispersion of predators into the marsh) is hypothesized to shape selection gradients in salt marshes, as inferred from the record of unsuccessful predation.     

Influence of halophytes and metal contamination on salt marsh macro-benthic communities

Since an important fraction of the organic matter produced by salt marshes is decomposed in situ, macro-benthic communities are particularly exposed to the trace metals retained by these systems. Yet, few studies have investigated the macro-benthic communities using the between-root sediment habitat of the salt marsh halophytes (salt-tolerant plants), or the effect of trace metal pollution on its population dynamics. In the present study, samples were collected in vegetated and unvegetated sediment, in three salt marshes in the Tagus estuary, for trace metal concentration determination in the sediment and in the halophytes roots, grain size determination and macro-benthic organism identification. Data analysis revealed that the distribution of macro-benthic organisms is mainly determined by metal contamination, metal type and by the presence/absence of halophytes, not by the halophyte species. Five different associations were identified: resistant organisms were associated with the highest concentrations of lead (sediment); tolerant organisms with zinc, copper (sediment and roots) and lead (roots); cadmium in the sediment with a lack of macro-benthic life; sensitive organisms with low levels of metals except for cadmium in the roots; and macro-benthos typical of intertidal mudflats with unvegetated areas with low metal contamination.     

A numerical study of tidal asymmetry in Okatee Creek,South Carolina

The Okatee River, South Carolina is characterized by a narrow tidal channel and an extensive area of intertidal salt marshes. Current measurements in the upstream portion Okatee Creek show that tidal flow features an asymmetric pattern: ebb current is stronger than flood current. The ebb dominance is mainly caused by deformation of the dominant astronomical tidal constituent M₂. An unstructured grid, finite volume coastal ocean model (FVCOM) with wet-dry point treatment method is applied to examine physical mechanisms of M₄ overtide generation. Model experiments show that mean absolute amplitude and phase errors are 3.1 cm and 1.7^° for M₂ elevation, 2.4 cm s⁻¹ and 0.8^° for M₂ current major axis, 2.1 cm and 1.8^° for M₄ elevation, and 2.1 cm s⁻¹ and 24.6^° for M₄ current major axis. The overall pattern of tidal asymmetry is qualitatively reproduced. Various sensitivity experiments suggest that the generation of M₄ overtide is a result of nonlinear interaction of tidal currents with irregular creek geometry and bottom topography. Consistent with the classical view, the large volume of intertidal water storage is the major reason for ebb dominance in the creek. However, the zero-inertia assumption (i.e., negligible advective terms) is probably not valid for the entire tidal cycle. Besides the pressure gradient force and the bottom friction force, terms related to lateral shear of the along-estuary velocity (i.e., advective inertia and horizontal eddy viscosity) may also contribute in horizontal momentum balance. Exclusion of the flooding-draining processes over the intertidal zone will severely underestimate tidal currents in the river channel and make the tidal asymmetry less prominent.