Cobalt sorption–desorption behavior of calcareous soils from some Iranian soils     

《Chemie der Erde / Geochemistry》2016,76(1):95-102

Little research has been done to study the role of soil parameters in cobalt (Co) retention, release and the processes involved in calcareous soils of arid and semi-arid regions. We studied the Co sorption and desorption capacity of various calcareous soils using batch technique. The sorption and desorption behavior of Co varied greatly among the studied soils. The sorbed fraction ranged from 92.3% to 97.2% and from 51.0% to 71.8%, when 5 and 200 mg Co l⁻¹, was added to the soil samples, respectively. Cobalt sorption curves were well fitted with Langmuir, Freundlich, and linear equations. The values of the distribution coefficients obtained from linear equation ranged from 9.5 l kg⁻¹ to 23.4 l kg⁻¹. Desorption experiments resulted in a Co recovery ranged from 3.6% to 11.4%, indicating a low desorption of Co from soils. The results of the geochemical modeling indicated that under low Co addition, the solutions were undersaturated with respect to Co(OH)_2(am), Co(OH)_2(c), Co₃(PO₄)_2(s), CoCl_2(s), CoHPO_4(s), CoCl₂·6H₂O_(s), and CoO_(s), whereas under higher Co addition, the solutions were undersaturated with respect to Co(OH)_2(am), CoCl_2(s), CoCl₂·6H₂O_(s), CoO_(s), CoHPO_4(s), and saturated with respect to Co₃(PO₄)_2(s), and CoCO_3(s). The hysteresis indices indicated that desorption of freshly sorbed Co with 0.01 M CaCl₂ was hysteretic in all soils and low mobility and leaching potential of freshly sorbed Co can be expected from these calcareous soils. Statistical correlations revealed that Co sorption and desorption onto the soils were influenced by the presence of CaCO₃ in soils. These findings suggested that calcareous soils are able to retain strongly Co in which the movement of Co in the soil profile would be negligible. Thus, little risk of groundwater contamination can be expected with Co in these calcareous soils.  相似文献   

Efficiency of rainwater harvesting of microcatchments and the role of their design     

《Journal of Arid Environments》2013

Microcatchment is a technique for collecting, storing and conserving local surface runoff in order to grow trees/shrubs. In this system, runoff water is generated on a plot and stored in the soil during runoff events, and trees/shrubs may utilize this water during the next dry season.Microcatchments have relatively small runoff generation areas (from dozens to hundreds sq. m) and are cheap and simple to implement Their collection area is usually a small depression located nearby the runoff generating area in which one or a few trees/shrubs may be planted Due to the short overland flow path runoff generation is efficient and even short low intensity storms may generate runoff. The drawback is however that due to the small size of the generating area small volumes of water are conveyed to the storage plots. Another drawback is susceptibility of the augmented water to evaporation. The main objective of present research presented hereafter was to estimate the effect the depth of the depression has on the efficiency of the water conservation in the soil profile. In the present study the storage plots were circular pits and the effect their depth had on evaporative losses and water distribution were studied.The results clearly show that the depth of the pit significantly affects evaporative water losses. The losses were separately computed for the soil cylinder whose upper surface is the bottom of the pit and for the surrounding shell. No differences between treatments were evident for losses from the inner cylinder. Significant differences in water losses were however observed for the surrounding shell where the shallow pits losing as much as six times more than the deeper pits.  相似文献   

Holocene climate variations from Zhuyeze terminal lake records in East Asian monsoon margin in arid northern China   总被引：4，自引：0，他引：4  

Hao Long  ZhongPing Lai  Yu Li 《Quaternary Research》2010,74(1):46-56

Zhuyeze palaeolake is a terminal lake situated in the arid northern China in the East Asian monsoon margin. In order to examine the Holocene palaeoclimatic change in the East Asian monsoon margin, Qingtu Lake section (QTL) from Zhuyeze palaeolake is sampled in high resolution. Palaeoclimatic proxies such as grain size, carbonate, TOC, C/N and δ¹³C of organic matter, were analyzed; eleven ¹⁴C samples and six optically stimulated luminescence (OSL) samples were dated to provide chronological control. We also investigated the geomorphic features of lake shorelines in this area. The results show that the climate was warm and dry in early-Holocene (9.5-7.0 cal ka BP), cool and humid in mid-Holocene (7.0-4.8 cal ka BP), and increasingly drier in late-Holocene (since 4.8 cal ka BP). Comparisons of our records with other records in adjacent areas, as well as with the records in the Asian monsoon areas, suggested that changes in effective moisture was synchronous in East Asian monsoon marginal zone (i.e. the pattern of dry early-Holocene, humid mid-Holocene, and aridity-increasing late-Holocene), and that the moisture optimum during the Holocene was out-of-phase between Asian monsoon margin and Asian monsoonal dominated region, possibly due to the high temperature at that time.  相似文献   

Abrasion-derived sediments under intensified winds at the latest Pleistocene leading edge of the advancing Sinai-Negev erg     

Yehouda Enzel  Rivka Amit  Onn Crouvi  Naomi Porat 《Quaternary Research》2010,74(1):121-482

Quaternary desert loess and sandstone-loessite relationships in the geological record raise questions regarding causes and mechanisms of silt formation and accretion. In the northern Sinai-Negev desert carbonate terrain, only sand abrasion in active erg could have produced the large quantities of quartzo-feldspathic silts constituting the late Quaternary northwestern Negev loess. In the continuum of source (medium to fine sand of dunes) to sink (silts in loess) the very fine sand is unaccounted for in the record. This weakens the sand abrasion model of silt formation as a global process. Here, we demonstrate that, as predicted by experiments, abrasion by advancing dunes generated large quantities of very fine sand (60-110 μm) deposited within the dune field and in close proximity downwind. This very fine sand was generated 13-11 ka, possibly synchronous with the Younger Dryas under gusty sand/dust storms in the southeastern Mediterranean and specifically in the northern Sinai-Negev erg. These very fine sands were washed down slope and filled small basins blocked by the advancing dunes; outside these sampling basins it is difficult to identify these sands as a distinct product. We conclude that ergs are mega-grinders of sand into very fine sand and silt under windy Quaternary and ancient aeolian desert environments.  相似文献   

我国干旱半干旱区降水的特征分析   总被引：9，自引：1，他引：9       下载免费PDF全文

任福民  史久恩 《应用气象学报》1995,6(4):501-504

利用聚类分析对全国160站1951～1992年的年降水标准化资料做分析，结果可划分为两大区——干旱半干旱区和非干旱区，在此基础上进行降水区划及降水分布型研究，得出我国干旱半干旱区大致分成9个小区以及它的3种年降水分布型式。  相似文献   

太湖东岸平原中全新世气候转型事件与新石器文化中断   总被引：27，自引：0，他引：27  

于世永  朱诚  曲维正 《地理科学》1999,19(6):549-554

来自苏州草鞋山遗址年代学,生物地层学和沉积学的分析结果表明,本区新石器文化演进与全新世气候突变的事件有关。高分辨率,连续的孢粉,粒度和磁化率记录证实,崧泽文化是在暖湿气候条件下出现和繁荣的,发生在５３６５ａＢ．Ｐ左右的一次干旱事件使之走向衰落,而出现在全新世大西洋期与亚北方期过渡阶段的一次气候转型事件中断本区文明达２００年之入。５１６０ａＢ．Ｐ．以后,气候转为暖干,经历了一次干旱事件后,良渚文化发  相似文献   

黑河实验(HEIFE)能量平衡和水汽输送研究进展   总被引：7，自引：1，他引：7  

胡隐樵 《地球科学进展》1994,9(4):30-34

It is a review about advance of research on energy budget and transportation of water vapour in the HEIFE area. A basic model, the cold island in oasis and the inverse humidity phenomenon in desert, about interaction of oasis with desert environment is established. The major disturbance of the oasis to observation in the desert is the latent heat flux that is an ignored value in the energy budget on ground surface in the desert. Consequently, it is representative of the arid region to have measured energy budget at the gobi station and desert station in the HEIFE area.  相似文献   

Mangos shale-associated alluvium     

Jonathan B. Laronne 《地球表面变化过程与地形》1981,6(6):541-552

Inquiry into the dissolution kinetics of naturally occurring geologic materials, rather than individual mineral species, has been relatively neglected. This is especially true of surface processes, the realm of surface water hydrology and geomorphology. This paper focuses attention at a laboratory study of the rate of such complex reactions. Functions defining the dissolution rates of saline (0.1–20 per cent salt content) Mancos Shale-associated alluvium in distilled water follow varying patterns. Dissolution is characterized by an initial (<5 min) high rate constant, by a following phase (20 min-57 h) where rates are reduced drastically, and by a final period of encroachment to equilibrium. Initial dissolution rates increase with increase in salt content and sediment: water ratio. The time necessary to approach equilibrium is, however, found to be directly proportional to the sediment; water ratio. The concentration of Na⁺, Mg²⁺, Ca²⁺, SC^2?₄ and HCO^?₃, and the relative abundance of Ca²⁺ and HCO^?₃ increase continuously with contact time, indicating that the hydrated sodium and magnesium sulphate minerals provide most of the initial solutes, though not necessarily most of the total solute bulk. The results obtained in this study indicate that the high initial dissolution rate of soluble minerals from alluvium, and particularly from shales in contact with aqueous solutions, is too short-lived to account for most of the solutes occurring in heavily sediment-laden surface flow. Excluding input from slower, usually supersaturated subsurface flow, dissolution from sediment in transport should be a major source of solutes in originally undersaturated and kinetically unequilibrated surface water in semiarid and arid regions.  相似文献   

Assessment of hydraulic properties of sedimentary and volcanic aquifer systems under arid conditions in the Republic of Djibouti (Horn of Africa)     

Mohamed?Jalludin  Moumtaz?RazackEmail author 《Hydrogeology Journal》2004,12(2):159-170

The Republic of Djibouti (23,000 km²; 500,000 inhabitants), located within the Horn of Africa, undergoes an arid climate with an average annual rainfall less than 150 mm. Water resources are provided up to 98% by groundwater. Two types of aquifers are encountered: volcanic and sedimentary aquifers. This paper focuses on the assessment of their hydraulic properties, which is necessary for future tasks regarding the management of these aquifers. To this end, a data base consisting of all available pumping test data obtained since the 1960s was compiled. Pumping tests have been interpreted to determine transmissivity. Solely for volcanic aquifers, transmissivity also has been estimated through an empirical relationship using specific capacity corrected for turbulent well losses. The transmissivity of each type of aquifer can span up to four orders of magnitude, pointing out their strong heterogeneity. For the various volcanic rocks, the younger the rock, the higher the transmissivity. The transmissivity of volcanic rocks has therefore decreased in the course of geological time. At present, a much better understanding of the hydraulic properties of these complex aquifers has been obtained, which should enable optimal management of their groundwater resources through the use of numerical modeling.

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Resumen La República de Yibuti (23.000 km², 500.000 habitantes) está situada en el Cuerno de África, donde se han formado diversas unidades volcánicas—basaltos y riolitas—y rocas sedimentarias desde la expansión de los continentes acaecida al inicio de la deriva continental (hace 30 millones de años). La precipitación media anual es inferior a 150 mm. Las rocas volcánicas y sedimentarias, con dimensión inferior a 2.000 km², constituyen acuíferos locales. Los basaltos estratificados forman un acuífero regional que se extiende a más de 9.000 km². La multitud de datos existente ha sido almacenada desde los años 1960 en una base de datos. La transmisividad de estos acuíferos ha sido determinada mediante datos de ensayos de bombeo y una relación empírica que usa la capacidad específica corregida con las pérdidas turbulentas en el pozo. La transmisividad de estos acuíferos se comporta como una variable lognormal, hecho importante para los trabajos previstos de modelación con métodos estadísticos. La transmisividad de cada acuífero puede variar hasta en cuatro órdenes de magnitud, manifestando su gran heterogeneidad. Para los materiales volcánicos, la transmisividad es mayor cuanto más joven es la roca. La permeabilidad de las rocas volcánicas ha evolucionado por tanto con el tiempo geológico. Actualmente, se posee un mayor conocimiento sobre las propiedades hidráulicas de estos acuíferos complejos, de manera que se puede hacer una gestión óptima de sus recursos hídricos subterráneos con la utilización de modelos numéricos.

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Résumé La République de Djibouti (23,000 km²; 500,000 habitants), située dans la Corne de lAfrique, subit un climat aride avec une pluviométrie moyenne annuelle inférieure à 150 mm. Les ressources en eau sont fournies à plus de 98% par les eaux souterraines contenues dans des aquifères sédimentaires ou volcaniques. Cet article a pour objectif lévaluation des propriétés hydrauliques de ces aquifères, étape indispensable pour entreprendre par la suite des études en vue de la gestion de ces aquifères. Une base rassemblant les données dessais par pompage disponibles depuis les années Soixante a dabord été établie. Les essais par pompage ont été interprétés pour déduire la transmissivité. Concernant les aquifères volcaniques, la transmissivité a également été estimée à laide dune relation empirique reliant la transmissivité et le débit spécifique corrigé des pertes de charge anormales. La transmissivité pour chaque aquifère couvre jusquà quatre ordres de grandeur, montrant la forte hétérogénéité de ces milieux. Pour les roches volcaniques, on observe que la transmissivité est dautant meilleure que la roche est plus jeune. Leur transmissivité a ainsi diminué durant les temps géologiques. La compréhension des propriétés hydrauliques de ces aquifères complexes est à présent bien meilleure, ce qui permet denvisager une gestion optimale de leurs ressources à laide de modèles numériques.

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国际干旱区研究发展态势简析   总被引：2，自引：0，他引：2  

张爱军 《干旱区地理》2006,29(3):452-456

基于SCI-E的国际干旱区研究科学计量指标明显上升,灰色预测显示未来仍将保持较大幅度的上升态势；美国是国际干旱区研究的科学活动中心,国际产出力指标居前的机构绝大多数出自美国；中国是国际干旱区研究产出力排名仅次于美国的第二大国；中国科学院是国际干旱区研究连续八年排名第一、产出力最高的科研机构；国际干旱区研究领域已经形成结构稳固、特征显著的核心支撑学科群。  相似文献