Desert Sand Dunes Research Articles

Should a doctor take into consideration the influence of climatic factors? Deliberations on the occasion of the publication of a new monograph (the book of essays of arid medicine by Z.R. Zununov, I.H. Nurov, and S.Z. Zununova)

The authors analyze the monograph of the Uzbek scientists professor Z.R. Zununov, I.H. Nurov, and S.Z. Zununova «Essays of arid medicine» (Tashkent: «KAMALAK-PRESS» publishing house, 2016;540). The book presents the results of the comprehensive bioclimatic assessment of the arid zones of Uzbekistan, their extreme climatic conditions (such as high intensity and solar radiation and the considerable duration of its period, dry air and summer heat, sandstorms (the so-called «Afghans»), and the great variety of the natural health-improving factors including mineral waters, microclimate of the speleotherapeutic cave, the desert dune sand, etc. The work is based on the authors' conceptual theory of «arid/meteorological stress syndrome», underlain by the hypothesis of the predominant role of hyperthermal weather hypoxia. A wide range of issues id discussed related to weather and climate adaptation of the healthy subjects (both indigenous and non-indigenous residents) and the patients suffering from ischemic heart disease, chronic obstructive pulmonary disease, and rheumatoid arthritis. Of special interest are the methods proposed for the correction of dysadaptive changes including the application of the natural balneotherapeutic factors existing in the arid zone (hydrogen sulphide and iodine-bromine balneotherapy, climatic therapy, speleotherapy, and psammotherapy (arenation). An important definitive conclusion at which the authors arrive is the necessity of the experimental observations in agreement with the requirements of the medico-biological ethics.

Effect of combined use of crushed sand and Algerian desert dune sand on fresh properties and strength of self-compacting concrete

Effect of combined use of crushed sand and Algerian desert dune sand on fresh properties and strength of self-compacting concrete

Observations and Prediction of Recovered Quality of Desalinated Seawater in the Strategic ASR Project in Liwa, Abu Dhabi

To be able to overcome water shortages, Abu Dhabi Emirate started an Aquifer Storage and Recovery (ASR) project with desalinated seawater (DSW) as source water near Liwa. It is the largest DSW-ASR project in the world (stored volume ~10 Mm3/year), and should recover potable water for direct use. DSW is infiltrated into a desert dune sand aquifer using “sand-covered gravel-bed” recharge basins. In this study, we evaluate the hydrogeological and hydrogeochemical stratification of the (sub)oxic target aquifer, and water quality changes of DSW during trial infiltration runs. We predict water quality changes of DSW after 824 d of infiltration, during 90 d of intensive recovery (67% recovered) without storage (scenario A), as well as after 10 years of storage (scenario B, with significant bubble drift). Monitoring of preceding trials revealed a lack of redox reactions; little carbonate dissolution and Ca/Na exchange; much SiO2 dissolution; a strong mobilization of natural AsO43−, B, Ba, F, CrO42−, Mo, Sr and V from the (sub)oxic aquifer; and immobilization of PO4, Al, Cu, Fe and Ni from DSW. The Easy-Leacher model was applied in forward and reverse mode including lateral bubble drift, to predict water quality of the recovered water. We show that hydrogeochemical modeling of a complex ASR-system can be relatively easy and straightforward, if aquifer reactivity is low and redox reactions can be ignored. The pilot observations and modeling results demonstrate that in scenario A recovered water quality still complies with Abu Dhabi’s drinking water standards (even up to 85% recovery). For scenario B, however, the recovery efficiency declines to 60% after which various drinking water standards are exceeded, especially the one for chromium.

New algorithms for predicting longitudinal motion resistance of wheels on dry sand

Predicting the resisting forces against a vehicle’s wheel during movement in loose sand is critical for optimizing tractive capabilities in desert regions, sand dunes, and beaches. We review existi...

Vulnerability of Different Geomorphic Units to Deserts in Parts of Western Rajasthan - A Study Based on Remote Sensing and GIS

Deserts are the areas of arid ecosystem which make vegetal and animal life difficult to sustain. The process which makes desert is called desertification. It also faces the loss of fertile topsoil at desert boundaries and usually caused by a combination of drought and the over exploitation of grasses and other vegetation by people. Desert sand dunes being soft, are more prone to erosion whether wind or water. Earth Observation Technology (EOT) by use of multi-sensor polar orbiting satellites is able to provide fairly good mapping and monitoring of deserts. An attempt to explore the potential of EOT in studying desertification nexus with geomorphic units in the area of Thar desert of Rajasthan, India has done.

Squeezing a rainfall record out of desert sand dunes

Squeezing a rainfall record out of desert sand dunes

A GIS add-in for automated measurement of sand dune migration using LiDAR-derived multitemporal and high-resolution digital elevation models

Desert environment modeling involving sand dune migration is important for better understanding of Earth and planetary surface processes. This paper presents a geographic information system (GIS) add-in for automated measurement of dune migration directions and migration rates using multitemporal, high-resolution digital elevation models (DEM) derived from light detection and ranging (LiDAR) data or other sources. Using the angle of repose (AOR) as a sensitive movement indicator of barchan (crescent-shaped) and transverse dunes, an add-in toolbar for ArcGIS was developed using the Python programming language to automatically detect, measure, and store dune migration direction and migration rate at random point locations on dune slip face centerlines. Pseudo-code and application samples from the White Sands dune field in New Mexico, USA, are also presented. The free add-in can be used by the geoscience community for studying coastal and desert sand dunes.[1][1] [1]: #fn-1

Hydraulic properties of dune sand–bentonite mixtures of insulation barriers for hazardous waste facilities

This paper presents a study on the valorization of local materials such as desert dune sand obtained from Laghouat region in the South Algeria and mine bentonite intended for the realization of liner base layers in the conception of insulation barriers for hazardous waste facilities. In practice, an economical mixture satisfying the hydraulic requirements is generally concerned. First, in order to get an adequate dune sand–bentonite mixture compacted to the optimum Proctor condition, an investigation on saturated hydraulic behavior is carried out in this study for different mixtures. Using oedometer test (indirect measurement), the adequate mixture of 85% dune sand and 15% bentonite satisfies the conditions of saturated hydraulic conductivity (k < 10−9 m/s). This result of the adequate mixture is also confirmed by direct measurement of saturated hydraulic conductivity using triaxial cell. Second, the unsaturated hydraulic conductivity of the adequate mixture is measured with an original vapor equilibrium technique (VET) used for Sr < 30% (very high suction s > 3 MPa). This technique is conducted based on the exploitation of the water retention curve in order to establish the relationships between hydraulic conductivity, degree of saturation, and suction. It shows that the hydraulic conductivity increases with the degree of saturation and decreases with the suction. However, the hydraulic conductivity has a constant value for suctions larger than 20 MPa. The selected dune sand–bentonite mixture satisfies the regulation requirements and hence constitutes a good local and economical material for the conception of barrier base liners.

Singing Sand Dunes

One of the highly striking yet poorly understood natural phenomena is the song of dunes. Some sand dunes in deserts are capable of emitting a loud persistent sound with a characteristic audible low-frequency (≈ 75—105 Hz), that can sometimes be heard up to 10 km away. Scientific in-vestigations suggest that the sustained low fre-quency sound of sand dunes that resembles a pure note from a musical instrument, is due to the synchronized motion of well-sorted dry sand grains when they spontaneously avalanche under gravity. This article describes the underlying mechanism for sustained sound emission in singing sand dunes in light of recent physical ex-periments.

Recovery of symbiotic nitrogen fixing acacia rhizobia from Merzouga Desert sand dunes in South East Morocco – Identification of a probable new species of Ensifer adapted to stressed environments

Bacteria capable of nodulating Acacia tortilis and A. gummifera could be recovered from sand dunes collected in the Moroccan Merzouga desert. The trapping approach enabled the recovery of 17 desert rhizobia that all clustered within the Ensifer (Sinorhizobium) genus. Four isolates of the dominant genotype comprising 15 strains as well as 2 divergent strains were further characterized by MLSA. Phylogenetic analyzes indicated that the dominant genetic type was belonging to a new and yet undefined species within the Ensifer genus. Interestingly, housekeeping gene phylogenies showed that this possibly new species is also present in another desert but in India. Phylogenetic analyses of nifH and nodC sequences showed high sequence conservation among the Moroccan strains belonging to the dominant genotype but high divergence with sequences from Indian isolates suggesting acquisition of symbiotic genes through Horizontal Gene Transfer. These desert rhizobia were capable of growing in media containing high salt concentrations, under high pH and most of the strains showed growth at 45°C. Only recovered from desert type of Biome, yet, this new taxon appears particularly adapted to such harsh environment.

Heritage Policies, Tourism and Pastoral Groups in the Sultanate of Oman

Abstract Although heritage and its preservation has been at the forefront of Omani policy for several decades, tourism to the country has been restricted, until recently, to small elite tour groups either taking advantage of the sun and sand or, in Dhofar, the cool and humid post monsoon landscapes. Pastoralist communities in the desert interior have been largely excluded from heritage tourism and tourist ventures with the exception of Disneyfied 'Arabian nights' camps on the edges of the most northerly desert sands of the Wahiba. Authenticity, and possession of intangible cultural heritage, for the most part have not been a part of tourism or, for that matter, heritage policies. The growing popularity of desert tours, camel racing and sand dune 'bashing' programmes in the neighbouring United Arab Emirates, is, however, changing perceptions and practices in Oman. The desert landscape and its intangible heritage are belatedly receiving some national and international attention. By focusing on notions of cosmopolitanism and tangible and intangible heritage, this paper will address the challenges that are emerging with regard to tourism, heritage and authenticity of the pastoral groups in the Sultanate of Oman. It endeavours to frame the heritage debates and national policies of exclusion of pastoral groups within the context of international demands for increased and accessible tangible and intangible heritage tourism.

Analysis of Desert Sand Dune Migration Patterns from Landsat Image Time Series for The Southern California Desert

Developers of renewable energy installations in southern California need to evaluate the risks to facility operations from proximity to active desert dunes. This study first validated Landsat image spectral data using ground-based data collection of aeolian sand migration rate measurements surveyed in Arizona as an accurate method for characterizing dune mobility. The predominant direction of measured sand dune movements was correctly mapped at this site from the satellite imagery, as well as the migration distances of the leading edges of sand dunes over the entire 1992-2010 monitoring period. Application of the Landsat image method to two dune systems in southern California demonstrated its usefulness for mapping sand migration patterns and rates. Between 1995 and 2014, Palen Dunes lost over half of its stable dune surface and increased its sand accumulation zone by nearly that same area coverage. In contrast, changes in the sand movement patterns at Kelso Dunes were not apparent, perhaps due in to its more constraining mountain landscape features. These results have an immediate application for understanding future sand transport and characterizing potential impacts to nearby utility-scale solar energy installations.

Microtopographic variation in soil respiration and its controlling factors vary with plant phenophases in a desert–shrub ecosystem

Abstract. Soil respiration (Rs) and its biophysical controls were measured over a fixed sand dune in a desert–shrub ecosystem in northwest China in 2012 to explore the mechanisms controlling the spatial heterogeneity in Rs and to understand the plant effects on the spatial variation in Rs in different phenophases. The measurements were carried out on four slope orientations (i.e., windward, leeward, north- and south-facing) and three height positions on each slope (i.e., lower, upper, and top) across the phenophases of the dominant shrub species (Artemisia ordosica). Coefficient of variation (i.e., standard deviation/mean) of Rs across the 11 microsites over our measurement period was 23.5 %. Soil respiration was highest on the leeward slope, and lowest on the windward slope. Over the measurement period, plant-related factors, rather than microhydrometeorological factors, affected the microtopographic variation in Rs. During the flower-bearing phase, root biomass affected Rs most, explaining 72 % of the total variation. During the leaf coloration–defoliation phase, soil nitrogen content affected Rs the most, explaining 56 % of the total variation. Our findings highlight that spatial pattern in Rs was dependent on plant distribution over a desert sand dune, and plant-related factors largely regulated topographic variation in Rs, and such regulations varied with plant phenology.

Linear and nonlinear wave propagation in booming sand dunes

The current field study examines linear and non-linear acoustic waves found in large desert sand dunes using field measurements of wave speed, frequency content, dispersion, and polarization. At the dune fields visited, an avalanching of sand can trigger a loud booming or rumbling sound with narrow peak frequencies centered between 70 and 105 Hz with higher harmonics. Prior to the onset of the nearly monotone booming, the emission consists of short bursts or burps of sound of smaller amplitude and over a significantly broader range of frequencies. These burps created at dune sites have similar frequency content to sounds generated by small-scale shearing in laboratory-scale experiments. By investigating the wave characteristics of both burping and booming emissions, this manuscript demonstrates that booming and burping correspond with the transmission of different waves within the dune. The burping sounds correspond to a surface Rayleigh wave with nonlinear and dispersive properties. The booming emission results from a linear, non-dispersive P-wave, which supports an earlier analysis where booming is modeled as the trapping of the body waves in the dune’s surficial layer. Besides characterizing the booming and burping emissions, this manuscript illustrates the effect of scale in the wave propagation of granular materials, when non-linear, dispersive waves across small scales transition to linear, non-dispersive waves across larger scales.

Singing Sand Dunes: The Spontaneous Acoustic Emission from Granular Shear Flow

One of the highly striking yet poorly understood natural phenomena is the song of dunes. Some sand dunes in deserts have a peculiar ability to emit a loud persistent sound with a characteristic audible low-frequency (75-105 Hz), sometimes can be heard up to 10 km away. Scientific investigations suggest that the sustained low-frequency sound of sand dunes that resembles a pure note from a musical instrument, is due to the synchronized motion of well-sorted dry sand grains when they spontaneously avalanche under gravity. This article describes the underlying mechanism for sustained sound emission in singing sand dunes in light of the recent physical experiments.

Community succession of bacteria and eukaryotes in dune ecosystems of Gurbantünggüt Desert, Northwest China.

Pyrosequencing and quantitative polymerase chain reaction of small subunit rRNA genes were used to provide a comprehensive examination of bacterial, cyanobacterial, and eukaryotic communities in the biological soil crusts (BSCs) of Gurbantünggüt Desert sand dunes (China). Three succession stages were recognized based on the analyses of eukaryotic communities: a late succession stage of BSCs in a swale with eukaryotes mainly related to the Bryophyta clade, an initial succession stage in a slope with barely any eukaryotic phototrophic microorganisms detected, and an intermediate succession type detected from both the swale and slope BSCs dominated by the phylum Chlorophyta. Moreover, the cyanobacterial community dominated all of the BSCs (48.2-69.5% of the total bacteria) and differed among the three succession stages: sequences related to Microcoleus steenstrupii and the genus Scytonema were abundant in the later succession stage, whereas both the initial and intermediate stages were dominated by Microcoleus vaginatus. Compared with swales, BSCs from slopes are exposed to a harsher environment, e.g., higher irradiance and lower water availability, and thus may be restricted from developing to a higher succession stage. Other disturbances such as wind and grazing may explain the different succession stages observed in swales or slopes. However, no clear differences were detected from non-phototrophic bacterial communities of the three succession stages, and sequences related to Alphaproteobacteria and Actinobacteria were most abundant in all the BSCs. The closest matches for the most frequent non-phototrophic bacterial genera were mainly derived from harsh environments, indicating the robustness of these genera.

Effect of fine aggregate replacement with desert dune sand on fresh properties and strength of self-compacting mortars

This paper presents the results of an experimental study that investigated the rheological and mechanical properties of self-compacting mortars incorporating fine dune sand (DS), which has a tight Particle size distribution. Mortar mixtures were prepared with crushed sand (CS) or river sand (RS) in which the fine aggregates were replaced partially by different percentages of DS of 0, 25, 50, 75 and 100%. The effect of DS on the fresh mortars properties was studied using the mini-slump flow, V-funnel flow time and viscosity measurements tests. Compressive strength and flexural strength were determined at age of 3, 7 and 28 days. Experimental results indicate an improvement in fresh rheological without reducing in mechanical properties of self-compacting mortars when fine aggregates were replaced partially with DS (50%). However, at high-level DS replacement (75%) the slump flow decreases. The replacement of the DS to the CS or to the RS shows an increase in the mixture viscosity. In general, the compressive and flexural strength were not significant affected with an increase in DS replacement. Finally, based on the results obtained in this investigation, DS may provide a readily available alternative material as fine aggregates in mortar application.

How do longitudinal dunes respond to climate forcing? Insights from 25 years of luminescence dating of the Australian desert dunefields

This paper presents a meta-analysis of 689 luminescence age estimates of Australian desert sand dunes. This analysis had two aims: to examine the hypothesis that Quaternary climate changes have forced dune accumulation, and to understand longitudinal dune behaviour from the age-architecture of sand dunes for which stratigraphic information is often absent or poorly known. A novel approach to the analysis of probability density curves of dune age frequency shows that in the Mallee dunefield of southeastern Australia only the period leading up to and including the last glacial maximum (LGM) (18–34 ka) experienced marked dune growth which cannot be explained by random stochastic activity. During the LGM, most, but not all, Mallee longitudinal dunes were accumulating more rapidly than before and after. In the Strzelecki dunefield source-bordering (SBD) longitudinal dune TL (n = 61) and OSL (n = 40) ages are more frequent at the Pleistocene–Holocene transition but nearby non-SBD longitudinal dunes (n = 21 ages) were only active above background levels during the LGM. However, the Strzelecki dune age data set suffers from being drawn from a small number of individual dunes (10 SBD dated using TL; 12 SBD dated by OSL; 7 non-SBD dated by OSL) with a marked bias away from surficial (young) and basal (old) depths. Even during the LGM, many dunes do not record active growth and the dunefield was most likely a mosaic of stable dune surfaces and bare mobile patches, supported by the scant pollen data from the arid zone. Hyper-aridity has not been experienced in these dunefields. These vegetated dunes exhibit conservative behaviour with limited response to the range of climate forcing experienced in the late Pleistocene. A more complete understanding of dunefield response to Quaternary climates would require an intensive and structured dating program to overcome the ‘noise’ from stochastic processes leading to small-scale activity in these dunes and the simultaneous removal of parts of the sedimentary record.

Change Detection of Desert Sand Dunes: A Remote Sensing Approach

Deserts are one of the major landforms on the Earth. While deserts occupy about one-fifth of Earth’s land surface, they have been studied to a much lesser extent. All over the world, desert landforms are expanding ever rapidly and more and more human settlements are finding place in desert regions for habitation. Thus, quantifying and monitoring dunes becomes more relevant from a managerial perspective. Analyzing desert areas using satellite imagery is a challenging task due to weak textural differences and nearly homogeneous spectral responses in most parts of the terrain. In this paper, a post-clustering methodology for change detection of desert sand dunes is proposed. Features based on Radon spectrum are used to cluster dunes of various orientations. These clustered boundaries are used to detect if there are any changes occurring in the dune regions. In the experiments, remote sensing data covering various dune regions of the world are observed for possible changes in dune orientations. In all the cases, it is seen that there are no major changes in desert dune orientations since three decades.

Formation and control of Turing patterns in a coherent quantum fluid

Nonequilibrium patterns in open systems are ubiquitous in nature, with examples as diverse as desert sand dunes, animal coat patterns such as zebra stripes, or geographic patterns in parasitic insect populations. A theoretical foundation that explains the basic features of a large class of patterns was given by Turing in the context of chemical reactions and the biological process of morphogenesis. Analogs of Turing patterns have also been studied in optical systems where diffusion of matter is replaced by diffraction of light. The unique features of polaritons in semiconductor microcavities allow us to go one step further and to study Turing patterns in an interacting coherent quantum fluid. We demonstrate formation and control of these patterns. We also demonstrate the promise of these quantum Turing patterns for applications, such as low-intensity ultra-fast all-optical switches.