One of the ways to improve the performance of simple solar stills is to use energy storage materials to store energy during the day and use it at night. Several energy storage materials have been studied by researchers, one of which is the use of sand. In this research, the improvement of a simple solar still performance has been studied using sand with different grain size distribution inside its basin. For this purpose, four solar still were made in Esfarayen (latitude 36. 20 and longitude 57. 67), Iran, and the effect of sand grain size distribution on its performance was studied in four treatments. The height of sand and water was 10 cm and the average grain size of treatments was considered 6. 9, 2. 8, 1. 1 and 0. 7 mm. The experiments were performed for 4 days in mid-August 2020. The results showed that the sand-containing treatment with an average grain size of 2. 8 mm had better productivity and thermal efficiency than other cases where the average grain size of the used sand was larger or smaller. Therefore, grain size distribution of the sand seems to affect the performance of simple solar stills and there is an optimal amount for grain size.

ABSTRACT The aim of the paper is to assess the morphological characteristics, mobility, and distribution of sediment particle size as maturity indicators of young dunes. The results indicated that according to the Equivalent Sand Thickness (EST) parameter and the wind direction variability parameter, the morphology of the sand dunes was determined as linear. The climatic index of sand dune mobility using meteorological data of Qom, Kashan, and Ardestan synoptic stations in a 27-year period showed that the sand mobility index (M) for sand dunes is 210, which is in the range of fully active dunes. The Grain Size Distribution and the scatterplots diagrams of sorting, skewness, and kurtosis versus the mean size of particles in differentiating the types of sand dunes showed that the relationship of sorting and skewness versus the mean size is effective in showing the dune's mobility. Sediment grain size parameters can be used as an indicator for transport environment and spatial changes. The studies of this research showed that based on grain size characteristics and climatic index, the sand dunes are the simple linear type with full activity. The transport environment in the dune sediments of the upwind sector is more energetic than the dune sediments of the downwind sector Extended Abstract Introduction Dune fields in arid and semi-arid regions typically form part of local to regional scale sand transport systems, which comprise source areas, transport pathways, and depositional sinks. The range of states of new sand dunes morphology and mobility generally follows the ratio between wind energy for sand transport, aeolian depositions characteristics, and many other environmental factors such as vegetation cover, humidity, and topography. Several parameters have been proposed to account for the morphology and mobility of the sand dunes. Wasson and Hyde considered dune forms as a function of the equivalent sand thickness (EST) parameter and wind direction change (RDP/DP) parameter. The range of states of dune mobility generally follows a climatic gradient. The climatic index of dune mobility developed by Lancaster has been applied to various environments. This index provides a measure of sand mobility (M) as a function of the ratio between the annual percentage of the time the wind is above the threshold for sand transport (W) and the effective annual precipitation (P/PE), where PE is potential evapotranspiration calculated using the Thornthwaite method. The grain size characteristics of the dune sands are closely related to factors such as the dynamic processes of the dunes, sand availability, vegetation, mode and distance of transportation from the source zones, and the energy conditions of the transporting medium. Textural and compositional variables widely used in grain-scale studies are the grain-size parameters (mean size, sorting, skewness, and kurtosis), and the specific gravity mean grain size is widely employed in dynamic interpretations, transport equations and sedimentary environment differentiation. Sorting is very useful in studies of sedimentary environments and aeolian dynamics. Dune sands tend to be better sorted than river sands. Skewness is likewise used to describe grain size distributions in aeolian environments and models to pattern the sediment transport trends. The distinction between the sand types can be numerically stated by computing the distribution curve's skewness (the third moment). On the phi scale, the skewness of dune sands is generally positive, whereas that of beach sands is generally negative. Finally, kurtosis is the less employed grain size parameter, and even Friedman (1961) affirms that it is not an environment-sensitive parameter. An aeolian sedimentary environment dominates the studied area and includes Active depositional dunes that have been formed in the last few decades. This research aims to analyze the characteristics of new sand dunes, including morphology, sediment physics, dunes mobility, and the relationship evaluation between factors to understand the nature of new sand dunes as one of the indicators of dry environments.   Methodology The characteristics of new sand dunes were evaluated based on meteorological, remote sensing data, observations, and field sampling. MODIS remote sensing data is used to study the sand dunes' morphology. The meteorological data were derived from two stations of Qom and Kashan. The analysis of the elongation and form of the dunes as the wind direction indicator showed that the area is affected by the winds region of the Qom. The samples were collected from linear sand dunes within varying morphologies. A total of 16 dune sites were studied. Grain size analysis of all samples was carried out using standard dry sieving and sedimentation techniques. Graphic grain-size parameters were estimated following Folk and Ward and using GRADISTAT software. The four size parameters were calculated, namely, mean size, sorting, skewness, and kurtosis. Scatter plot diagrams of mean size versus sorting, skewness, and kurtosis were plotted as scatter diagrams to evaluate their interrelationship and effectiveness in differentiating between the various sand dunes.   Results and Discussion Anemometry analysis shows that the wind in the region blows from three directions as westerly, north-westerly, and easterly, respectively, based on frequency and speed. Sand-moving winds in the area are strongly controlled from two primary directional sectors, westerly and north-westerly. Total potential sand transport (drift potential, DP) ranges from 202 (Qom station) to 87 (Kashan station) vector units (VU). Different types of sand dunes were identified in Erg Absherin; (a) prebarchanic dunes, (b) wedge-shaped dunes, and (c) simple immaturity linear dunes to silk dunes. The grain size distribution of the samples showed that the sand dunes have an average size range of medium to fine sand. The histograms of the size distribution indicated that they are all unimodal, with a modal class varying between medium to fine sand size. The sands of the studied dunes are poorly sorted; they range in size from 0.46 to 1.12 phi. The young and immature dunes of the northern area are relatively less sorted than the mature dunes. The interrelationship between mean size and skewness shows a general trend of skewness from medium to fine particles. Positivity of skewness increases with the increase in the mean grain size. In the same way, a general decreasing trend is recognized in the interrelationship between mean size and kurtosis, so sediments with a smaller mean size (larger phi) have leptokurtic. The state of dune mobility was determined based on the Lancaster dune mobility index test. The data showed that the sand mobility index (M) for sand dunes is 210, which is in the range of fully active dunes.   Conclusion The landscape of Kashan deserts is dominated by desert sand dunes, which occupy a considerable area of this region. Many of these new dunes have been formed and developed in the last few decades. Therefore, they provide the form and aeolian deposits with special features. The immaturity of crescent-shaped sand dunes (prebarchanic) to Seif dunes, lack of vegetation cover, and topographical characteristics indicate that the Erg is active. The spatial distribution of sand dunes showed that the linear morphology is consistent with the behavior of Qom station's wind and sand flux patterns. The harmony of the wind and storm rose patterns indicated that both effectively shape the dunes. The value of the dune mobility index exhibits that the dunes are fully active. The Aeolian Sediment Availability was compared with Glaser's diagram. Most of the samples were located in the aeolian mobility sector according to Gläser criteria. In terms of grain size distribution, there are differences in the grain size distributions for different dune types. The dunes are mostly composed of medium to magnificent sands. The sorting parameter indicates that the sands on the southern dunes (downwind) are better sorted than on the northern dunes (upwind). Under the conditions of low wind activity in the south of Erg, the frequency of finer particles and better sorting will increase. In general, the study of the analysis of this new and young Erg indicates that the dunes are characterized by linear or elongated, active, and mobile in an Aoelaian high-energy environment with sands of medium to fine, poorly to moderately well-sorted and finely skewed.   Funding There is no funding support.   Authors’ Contribution All of the authors approved the content of the manuscript and agreed on all aspects of the work.   Conflict of Interest Authors declared no conflict of interest.   Acknowledgments We are grateful to all the scientific consultants of this paper.

Removal of particles by filter is a complex water treatment process. Several factors are involved that include shape and size of filter grains, particle concentration, filtration velocity, and filter depth. The objective of this study was to evaluate particle removal efficiency (h) by changing particle concentration and media grain size in a rapid sand filter. Five concentrations (100, 200, 300, 400, and 500 ppm) of Kaolin particles and three mean media sizes (0.51, 1, and 1.41 mm) were used. The filter depth and the filtration velocity were 25 cm and 0.086 cmsec-1, respectively. Silica sand was used as the filter medium in all the experiments. The results showed that for the filter medium with an average grain size of 0.51 mm, removal efficiency increased with increasing influent particle concentration during the initial hours of filtration. Generally, suspended solids removal efficiency was higher at low particle concentrations. No significant differences were observed in removal efficiency for the three media sizes and particle concentrations of up to 300 mg/L, but for concentrations above 300 mg/L, removal efficiency decreased, especially for filter media with an average grain size of 1.41 mm. Removal efficiency decreased in filter media with average grain sizes of 1 and 1.41 mm at high particle concentrations from the very initial hours of filtration. The highest removal efficiency was observed in the filter medium with an average grain size of 0.51 mm. Differences in removal efficiencies between the filter media with average grain sizes of 0.51 and 1 mm were much greater than those between filter media with average grain sizes of 1 and 1.41 mm. In other words, the critical grain size for the filter medium was 1 mm.

This study provides novel insights into the shear resistance behavior at the concrete-sand interface, focusing on the combined effects of sand grain size, concrete surface roughness, and soil relative density. While individual parameters have been explored in previous research, this work systematically examines their interactions to better understand interface shear strength. A series of large direct shear tests was conducted on concrete-sand samples with varying surface roughness values (Rmax = 0, 0.2, 4, and 8 mm) and granular materials with different mean particle sizes (D50 = 0.25 mm, 0.8 mm, and 2 mm). The granular materials were compacted to different relative densities (Dr = 30%, 60%, and 90%). The results revealed that increasing relative density from 30% to 60%, and from 30% to 90%, led to substantial rises in interface friction (approximately 105% and 306%, respectively). Coarser sand exhibited a more pronounced increase in interface friction angle than finer sand. Furthermore, increasing concrete surface roughness from 2 mm to 8 mm resulted in a 27% increase in the friction angle. These findings highlight the significant role of these parameters in governing the interaction between concrete and granular soil, offering valuable insights for applications in civil engineering.

Using additives can improve the mechanical properties of soils of construction projects such as irrigation canals. The materials such as sand, in addition to improving soil conditions, are compatible with the environment. So, in recent decades, the utilization of sandy soils in the construct of irrigation networks has been extended. In this study, the effect of size and amount of sand on the strength characteristics of lime treated soils. In this way, at first, to determine the best soil-lime mixture, the soil was mixed by different amount of lime and unconfined compressive strength of these has been investigated. The highest unconfined compressive strength was achieved by adding 7 percent lime to the soil. Then, a set of tests conducted on coarse (D50= 1. 4 mm), medium (D50= 0. 45 mm) and fine (D50= 0. 22 mm) and by applying 5, 10 and 15 percent of sand to lime-clay mixture in three replicates. The unconfined compressive strength was performed on the specimen at curing time of 7, 14 and 28 days. Results showed that adding 5 percent of coarse sand to clay– lime mixture can increase compressive strength and elasticity module about 13 percent and 16 percent, respectively, on average. In addition, adding medium and fine sands can cause to deteriorate soil’ s strength and elasticity module.

Introduction: nZVI particles are strong reducing agents, capable of degradation and detoxification of a wide range of organic and inorganic pollutants in contaminated aquifers. Understanding the transport and retention of these nanoparticles in subsurface environments is required for treatment systems and in situ groundwater remediation. During the last decade, several studies have been conducted to investigate the effect of different physicochemical conditions on the transport and retention of nZVI in saturated porous media. This study aimed to evaluate the effect of sand grain size and nanoparticle concentration on fundamental processes governing CMC-nZVI nanoparticle transport and retention in saturated porous media. Materials and Methods: nZVI (NANOFER STAR, NANOIRON, s. r. o. Czech Republic was employed in this study. To prepare CMC-nZVI, nanoparticle, suspension and polymer solution was added by the relative dose of CMC to nZVI mass 1: 2, in a 250-ml flask reactor. pH was fixed at 9. 5 by NaOH and the solution was mixed for 144 h under ambient temperature condition at the absence of oxygen. Quartz sands with ∼ 99. 38% SiO2 and 0. 27 Fe2O3 based on XRF analysis, was used as the porous medium. The experiments were conducted using a cylindrical Plexiglas column 30 cm in length and 2. 5 cm in inner diameter. In order to capture the effect of particle concentration and grain size, 12 tests were conducted with four different concentrations (C = 10, 200, 3000, 10000 mg/l) and three sizes of grain (dc = 0. 297– 0. 5 mm, 0. 5– 1 mm, 1– 2 mm). In each test, ∼ 4 PVs of nZVI suspension were introduced into the columns and to complete the test, ∼ 6 PVs of deionized water were flushed. The column effluent was collected every 2 min and analyzed for total Fe using UV-Vis. The normalized effluent iron concentration (C/C0) for each transport test was plotted as a function of pore volumes. The spatial distributions of retained CMC-nZVI in the sand columns were determined to right after the breakthrough experiment. The quartz sand in each column was carefully excavated in ~3 cm increments, transferred into 50 mL vials and analyzed for total Fe. The concentration of retained CMC-nZVI in all the sand columns was also plotted as a function of travel distance. Results and Discussion: The breakthrough curves indicate that both grain size and nanoparticle concentration had a relevant impact on CMC-nZVI mobility, even if the influence of nanoparticle concentration was more evident. In all experimental conditions, the BTCs were not symmetrical, which indicates that attachment and detachment phenomena occurred in different modes. The breakthrough curves can be interpreted in two steps: injection and flushing times. The maximum relative concentration (C/C0) decreased, during injection time, for three different grain sizes while influent concentration increased from 10 to 10, 000 mg/L, which can be attributed to the increase in particle-particle interaction (aggregation) and particle-sand interaction (attachment). The breakthrough curves, after the initial increase, showed a strong decline, which is a clear indication of the ripening phenomenon. This phenomenon affected the porous medium properties such as porosity and hydraulic conductivity. Moreover, At higher influent CMC-nZVI concentration, Na+ ion and subsequently ionic strength increases because of higher doses of Na-CMC. As a result, aggregation and deposition will occur under a shallower secondary energy minimum well, that they are reversible. At the same nZVI concentrations, the breakthrough curve decreased by a decrease in grain size. Decreases in grain size can lead to an increase in surface area, decrease in pore throat size; and consequently, retention of nanoparticles by straining phenomena. However, another behavior was governed during the flushing time. During the flushing time, a narrow sharp increase in C/C0 was observed called flushing peak. In this study, CMC-nZVI aggregates deposited onto surfaces of sands due to secondary energy minimum were eventually released during the flushing period of the column with DI water. The results suggest that the grain size and particle concentration can have a positive effect on this peak. The results of retention profiles demonstrate that the CMC-nZVI retention in low concentration (10 mg/L) is consistent with filtration theory; whiles the highly concentrated polymer-modified nZVI dispersions (especially 3000 and 10000 mg/l) contradicts filtration theory. Based on filtration theory (Elimelech et al. 1995; Tufenkji et al. 2004), if all factors affecting the transport of colloids are kept constant, grain size increase can lead to a decrease in surface area and attachment efficiency (α ). The contradiction at high concentration can be explained by considering the effect of hydrodynamic forces (especially fluid shear) on agglomeration and disagglomeration and deposition and detachment. The size of stable aggregates formed in the pores of finer sands is smaller than when they are formed in the pores of larger sands because the magnitude of local shear is higher for narrower pores. This led to decreased retention in finer sand. Conclusion: The results of this research show that during the injection time, ripening and straining phenomena are key retention mechanisms of nanoparticles by decreasing the sand size and increasing particle concentration. While during the flushing time, secondary energy minima and hydrodynamic forces play critical roles in the deposition and transport mechanisms of CMC-nZVI. At high particle concentration (3000 and 10000 mg/l), these factors can lead to an increase in nanoparticle mobility by decreasing sand size. However, the results of retention profiles were consistent with colloid filtration theory at low particle concentration (10 and 200 mg/l).

One of characteristics studied in many researches on desert and arid zone such as study of ergs, Aeolian erosion, moving of sand dune, etc is grain size and morphoscopy. This study, as first step, is done in Iran for recognition of many regions especially in different ergs but, there is still a necessity of comprehensive research on Iran ergs and calculation of correlation among this characteristic with the others such as transition distance, sorting, etc. In this research, the mean of diameters of particles, the mean of mode of particles, the mean of skew ness in normal charts of particle diameters and the mean of distance moving of internal and coastal ergs were compared. There were no significant differences in the mean of diameter, the mean of skew ness, the mean of distance moving in internal and coastal ergs. But the mode of particles diameter was shown to have difference. The mean of diameter in internal ergs is varied from 74 µ to 689 µ and in coastal ergs is from 100 µ to 744 µ. 31% of mode of diameter in internal ergs is classified in class of 75 µ, 63% in 150 µ, 2% in 300 µ and 4% in 600 µ. These amounts are different in coastal ergs as 18% for class of 75 µ, 73% for 150 µ and 9% for 300 µ. The skew ness in internal ergs is varied from -0.2 to 2.95 and in coastal ergs from 1.31 to 2.71. The mean of moving distance has 4 classes consisting of 3, 12.5, 35, and 125 Km for internal ergs are 4, 2, 63 and 31% and for coastal ergs are 0, 9, 73 and 18%

Introduction: More than two thirds of Iran located at the arid and semi arid areas. Deficit of precipitation, reduced biodiversity and low density of vegetation. Poor vegetation allows to the wind to easily erode the soils and removes surface soil, from source areas and move to other places. In wind erosion we can recognize tree zones, Detachment zone (deflation and Afflation), transportation and accumulation. Preventing of movement of aeolian sediment from source region is a basic task and executive operations have to concentrate at the source region. In order to stabilization of source region of sands, identification of sources areas are necessary.

The objectives of this study were to determine the nature (aeolian vs. alluvial) and origin of sandy sediments in southwestern Iran (Khuzestan province) were collected in two transects across (NW-SE directions) and perpendicular to the Karkheh River, by using grain sized distribution characteristics, and the mineralogy and micro-texture of quartz grains of forty-five surface samples (0-30cm) at interval distances of ~1. 5km. Standard sieves (0. 5phi-intervals) were used for determining sand fractions. Silt and clay fractions were measured using the pipette method. Mineralogical composition and surface micro-texture of quartz grains of the selected samples were examined using a polarizing microscope and a scanning electron microscope, respectively. Mz (mean grain size) varied between 1. 82 to 4. 56 . The variations of Mz indicated the directional particle size fining the NW-SE transect. Sorting ( I) was 0. 46 to 2 and with an average of 0. 97 was poorly to well sorted. The mean value of skewness (SKI) was 0. 12 which ranged from-0. 24 to 0. 46 and skewed to fine particles. Kurtosis with mean values of 1. 21 varied between 0. 85 to 2. 25, which indicated a slight leptokurtic. Grain size characteristics showed a disturbance near the river due to the fluvial processes. Quartz grains were rounded and evidences of both aeolian and fluvial processes were observed on the grains’ micro-texture. The mineralogy of sediments were similar to those in Saudi Arabia. This mineralogical similarity, as well as prevailing wind direction and grain size variations, indicates the possibility of the sediments to have likely originated from the Arabian plate.

The southwest province of Iran has a dry and semi-arid climate, with about 250, 000 hectares of sand dunes; therefore a comprehensive review and overview of these features and their correlation with other features is needed. In this study, over 200 sand samples were collected from the mobile and not mobile sand dunes to study the grain size of sand dunes in Khuzestan. The results showed there was no significant difference in the mean grain size from east to west, along a 200 km transect of the sampled area. The mean grain size in the west was 2. 87 to 2. 14 φ scale (136 to 226 microns) and in the east 3. 05 to 2. 16 φ (120 to 223 microns). The standard deviation of particle size of the samples was good and fairly good (0. 71 to 0. 35 φ ). Using tilt condensation particle diameter in the range of sand dunes area, folk scale (0. 1 to 1 φ ) was positive. These distances represent 20 to 50 km with mean transported distance of 35 km for the west and 50 to 200 km transported distance with mean value of 125 km for the east section of the Khuzestan province for the sand dunes. For the transport distances, average transport distance could be divided into four categories, including 3, 12. 5, 35 and 125 km. According to the results, the source of particles of the sand dunes in Khuzestan province is local, mainly from northwest and west.