Sand Fixing Research Articles

Impacts of forest age on soil characteristics and fertility quality of Populus simonii shelter forest at the southern edge of the Horqin Sandy Land, China.

The sand fixing shelter forests in the Horqin Sandy Land are a key area in the "3-North" Shelter Forest Program in China, which has a history of over 50 years of artificial afforestation. Populus simonii Carr is one of the most dominant silvicultural species in the region. The aim of this study is to understand the soil characteristics and soil fertility of Populus simonii shelter forests at different growth stages and to establish a scientific basis for soil nutrient regulation and sustainable management of Populus simonii shelter forests at the southern edge of the Horqin Sandy Land. Sample plots were selected for young (≤15 a), middle-aged (16-25 a), near-mature (26-30 a), mature (31-40 a), and over-mature (≥41 a) forests. Each forest studied was in a state of natural restoration with uniform stand conditions and no artificial fertilizer was applied. These sites were selected to study changes in the soil characteristics in soil depths of 0-20, 20-40, and 40-60 cm. In order to avoid the problem of multicollinearity between soil variables and to reduce redundancy, principal component analysis (PCA), Pearson's correlation analysis, and Norm value calculation were used to select the least correlated indicators with the highest factor loadings. This was used to establish the minimum data set. The soil fertility quality of these shelterbelts in different forest ages was quantified using the soil quality index (SQI). In the growth stage from young to nearly mature forests, the soil bulk weight and pH decreased with increasing forest age. Soil capillary porosity, noncapillary porosity, total porosity, water content, field water holding capacity, and organic carbon content increased with increasing forest age and soil nutrient content gradually improved. At the stage of near-mature to over-mature forests, the effect of forest age on soil bulk density was not significant and all other soil characteristics decreased to varying degrees as the forest age increased. The soil also developed from alkaline to neutral. The SQI of the total data set and the SQI of the minimum data set consistently showed that near-mature forests (NMF) > middle-aged forests (MAF) > mature forests (MF) > over-mature forests (OMF) > young forests (YF). The results of the two evaluation systems showed a significant positive correlation (P < 0.05, R 2 = 0.8263) indicating that it is feasible to use the minimum data set to evaluate the soil fertility of shelter forests of different forest ages. The age of the forest has an obvious effect on the soil characteristics and overall soil fertility of shelter forests. The Populus simonii shelter forests on the southern edge of the Horqin Sandy Land have great soil development at the early stage of afforestation and the soil nutrient content gradually increases. The soil fertility reaches a peak when the forest is nearly mature and the soil fertility declines after the age of the forest reaches 30 years.

Characteristics of wind-sand transportation along railways in the eastern fringe of the Taklimakan Desert and sand control system

Abstract This paper focuses on the Korla-Ruoqiang desert railway line, utilizing ERA5 (ERA5 is the fifth generation of ECMWF (European Centre for Medium-Range Weather Forecasts) atmospheric reanalysis global climate data) wind data to conduct a comprehensive analysis of the wind energy environment along the line in all aspects, reveals the characteristics of wind-sand transport, and puts forward the countermeasures to prevent and control wind-sand disasters. The results of the study indicate that: (1) the wind-sand along the line mainly occurs in the spring and summer seasons, and the dominant sand-moving directions are easterly (ENE, E and NNE) and northeasterly (NE). (2) The average annual sand-moving wind speed ranges from 5.80 m/s to 7.25 m/s, and the annual frequency of sand-moving ranges from 11.99% to 37.26%. (3) The annual sand drift potential (DP) along the line ranges from 69.20 VU to 607.24 VU, with three types of wind energy environments: low, medium and high. The resultant drift potential (RDP) ranges from 45.52 VU to 547.49 VU, and the wind variability index (RDP/DP) is between 0.54 and 0.90. (4) The average sand transport quantity along the line ranges from 2.92 m³/m/a to 9.09 m³/m/a. Based on these results, we optimize the sand blocking, sand fixing and wind erosion prevention measures for different types of wind-sand environments, establish a scientific and efficient wind-sand protection and control system to solve the wind-sand problems and provide a scientific foundation for the prevention and control of wind-sand disasters along the line.

The assessment of ecological restoration effects on Beijing-Tianjin Sandstorm Source Control Project area during 2000–2019

To halt the trend of desertification and improve the ecological environment in Beijing, Tianjin and surrounding areas, China establishes the ecological engineering of Beijing-Tianjin Sandstorm Source Control Project. The assessment of ecological restoration after the implementation of ecological engineering is conducive to the ensuing management of ecological engineering. Based on a large number of remote sensing data and calculation models, this study selected land use/cover, vegetation ecological quality indicators such as vegetation coverage and NPP, and other ecological service indicators such as water retention calculated by the InVEST model, soil retention by the RUSLE model, and sand fixing services by RWEQ model to comprehensively assess the degree of restoration and trend of ecological engineering implementation. The contributions of climate change and human activities to NPP and soil retention services are also assessed. We found that from 2000 to 2019, the land cover pattern is optimized, with desert and farmland turning to grassland and forest. The vegetation ecological quality has been improved, sand-fixing service have been significantly improved, and water retention and soil retention service are degraded in some areas. The areas with a high-degree restoration are mainly located in the water source protection areas in the Yanshan mountainous region and in some areas in the south-eastern Horqin Sandy Land, while the areas with a low-degree restoration are mainly located in the desert grassland. The ecological improvement areas are mainly distributed in the mountains in norther Shanxi Province, the water source protection area in the Yanshan mountainous region, the Southern Great Hinggnan Mountains and part of the agro-pastoral transitional grassland. The highly degraded areas are mainly concentrated in the middle of Horqin and Otindag Sandy Lands. Ecological engineering plays an important role in promoting ecological restoration by changing land use types. The contribution proportion of climate change to NPP and soil retention services are significantly higher than those of human activities. The degree of ecological restoration depends on the climax ecological background determined by the climate.

Straw checkboard or Afforestation?—Assessment and comparison of combined benefits of two typical sand fixing models

Land desertification and sandstorms have been affecting cities worldwide on the edge of sandstorms, so humans have been seeking for ways to strengthen their defenses against wind and sand. High water retention capacity can improve human well-being in sandy areas. Several measures and cases have been already developed. To systematically find the differences between different ecosystem restoration models according to integrated benefits (e.g., ecological, economic and social benefits), this paper proposes an effective technical methodology to quantitatively identify sand control projects in a certain area. With the Southern edge of Tengger Desert-Shapotou in China as an example, this paper uses land use change and NDVI change rates to identify areas of wind and sand management. In addition, this paper uses actual evaporation (ET), soil moisture (SM), temperature vegetation dryness index (TVDI) and sand fixation service to compare the advantages and disadvantages of two typical sand management models in China according to their wind and sand control benefits, resource conservation, as well as socio-economic benefits. As indicated by the results, the straw checkboard engineering model has sustainable ecological and socio-economic benefits in water retention, cost consumption, as well as wind and sand control. Besides, the afforestation model achieves higher ecological benefits in the short term, whereas it has higher operating costs and poor sustainability, which makes this model difficult in maintaining ecological stability. On the whole, both types of sand control projects show their advantages and disadvantages in wind and sand control functions, resource recycling and socio-economic benefits. Furthermore, fast-growing afforestation combined with straw checkboards is capable of sustainably resisting wind and sand attacks and preventing land desertification. Accordingly, the finding of this paper can be referenced widely for wind and sand control.

Natural Deterioration Processes of Salix psammophila Sand Barriers in Atmospheric Exposure Section.

The atmospheric conditions of desert environments are important for the protection of Salix psammophila Sand Barrier, and these conditions can affect and change the structure and performance of the sand barrier, causing them to lose their wind proofing and sand fixing benefits. In this study, we have first examined the key environmental factors that affect the exposure of S. psammophila sand barrier. Then, we assessed how key factors in the desert atmospheric environment affect structural aging and performance. The relative crystallinity and chemical composition changes in the sand barrier were measured by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), and the main degradation factors and processes were discussed. The results showed that the degradation degree of the exposed S. psammophila sand barrier was mainly affected by moisture and ultraviolet radiation. Lignin was the main component and the source of photodegradation and photodiscoloration observed in the sand barrier. However, other polysaccharides, such as cellulose and hemicellulose, were less affected by photodegradation. The stress generated by alternating desorption-absorption was the main cause of the expansion and contraction, deformation, cracking, and warping observed in S. psammophila sand barrier. We also found a series of irreversible changes and losses that occurred, which affected the natural material properties of S. psammophila sand barrier exposed to atmospheric conditions for several years. Exposure times between 5 and 7 years were the most important turning point in time for determining the deterioration of the S. psammophila sand barrier. Our results highlighted the importance of the interactions between atmospheric factors and the exposed atmospheric sections of the S. psammophila sand barrier from the perspective of environmental effects. However, the exact mechanisms of the sand barrier deterioration still need further investigation. Nevertheless, our overall findings advanced the current understanding of the environmental effects of S. psammophila sand barrier for ecological restoration and desertification reversal, especially in stressful desert environments.

Research on Factors Affecting Cutting Resistance of Cutting Blade Based on Sand Trough Test

The use of sand fixing equipment to lay straw checkerboard barrier has become the main means of desert control, while the design of laying system for sand fixing equipment lacks relevant theoretical guidance. The factors that influence the cutting resistance are complex in the process of laying straw checkerboard barrier. A sand trough test-bed was designed to study the factors affecting the cutting resistance in the blade cutting process. The structure of the test platform was composed of disc knife, sand tank, bracket, lifting slide rail device, force measuring device, driving device, etc. By establishing the mathematical model of the working force of the cutter, the diameter of the cutter was determined as 720 mm and the thickness of the cutter was 6 mm. The water content of the tested sand was 6.3%, the wet density was 1.141%, and the dry density was 1.140%. The sand barrier material was selected from the natural dry rice straw, the diameter of the single straw was about 4 ∼ 5mm, the length of the straw was about 700 mm, and the quality of the single rice straw evenly laid 1000 mm was 160 g. The driving device chose the stepping motor as power source, which can drive the lifting slide rail device moving in horizontal direction. The tension pressure sensor of the force measuring device was installed by articulated form, which can obtain test data. The parameters of the speed control system were calculated and the schematic diagram of the drive was designed, and the laying speed could be adjusted by adjusting the frequency of the stepping motor. The influence of the change of inserting depth, laying speed and laying thickness on the insertion resistance of the cutter disc were tested. Inserting depth and laying thickness had significant influence on insertion resistance and traction force. When the thickness of the thickness was 160 g/m and the insertion depth was 150 ∼ 210mm, the insertion resistance was around 1700 ∼ 2450 N, and the traction value was between the 550 ∼ 1200 N. When laying thickness reached 480 g/m, the insertion resistance reached about 3200 N, traction was up to 1600 N. According to the orthogonal test results, the best combination was insertion depth of 210 mm, laying speed of 0.056 ∼ 0.112m/s, and laying thickness of 480 g/m. The order of the main and secondary factors affecting the test results was the maximum insertion depth, the laying thickness and the minimum laying speed. A regression model between insertion resistance, traction force and insertion depth and thickness was established, and relevant experiments are carried out to verify the rationality of the model. It was found that the laying speed had little effect on the test results. The laying thickness had a more significant impact on insertion resistance, while insertion depth had a more significant impact on traction force according to the surface of double parameters. The experimental results provided a theoretical basis for the design of the laying and the traction power system of sand fixing equipment.

Microbially Induced Magnesium Carbonate Precipitation and its Potential Application in Combating Desertification

This study investigated the reaction processes of microbially induced magnesium carbonate precipitation (MIMP) with Sporosarcina pasteurii (ATCC 11859) and evaluated its feasibility for controlling desertification in the desert areas in Northwest China. We explored systematically bacterial growth curves, mineralogy of precipitates, and relative chemical conversion efficiencies of the reaction using magnesium carbonate and bacterial urea hydrolysis with Sporosarcina pasteurii. We also compared the results of MIMP with the previously, well-studied microbially induced calcium carbonate precipitation (MICP). Our results indicate that excess Mg2+ motivated bacterial growth slightly. Magnesium carbonate precipitates appeared as nesquehonite, Mg-amorphous calcium carbonate, and Mg-rich calcite. The relative chemical conversion efficiency was higher in Mg medium than in Ca medium. We next evaluated the potential of using MIMP to mitigate desertification. We validated our results using the Mg-rich solution obtained by dissolving abandoned Mg salts that formed from the potassium salt plants nearby salt lakes. MIMP could potentially overcome shortcomings of traditional sand fixing methods, and was particularly suitable for controlling desertification in desert areas in Northwest China where there are abundant Mg resources. If MIMP works at field scales, this approach would further benefit ecosystem reconstruction because MIMP has main products of organic nutrients and ammonia, which would facilitate the development of biomass and soils. Overall, this work provides new insights into MIMP and its geoengineering potential in controlling desertification.

Optimization designs of artificial facilities in deserts based on computational simulation

Sediment transport of sand particles by wind is one of the main processes leading to desertification in arid regions, which severely impairs the ability of mankind to produce and live by drifting sand into settlements. Optimization designs of artificial facilities have lately attracted extensive interest for human settlement systems in deserts because of their acceptable protection effect, convenience of implementation, and low material cost. However, the complexity of a settlement system poses challenges concerning finding suitable materials, artificial facilities, and optimization designs for sand deposition protection. In an effort to overcome these challenges, we propose a settlement system built with brick, solar panel, and building arrays to meet the basic needs of human settlements in arid regions while preventing wind-sand disasters. The wind flow and movement characteristics of sand particles in the brick, panel, and building arrays were calculated using computational fluid dynamics and discrete phase model. The performance of three types of arrays in wind-sand flow in terms of decreasing the wind velocity and sand-particle invasion distance was evaluated. The results show that the wind velocity near the surface and the sand invasion distance were significantly decreased in the space between the brick arrays through properly selected vertical size and interspaces, indicating that the brick arrays have an impressive sand fixing and blocking performance; their effective protection distance was 3–4 m. The building arrays increased the near-surface wind velocity among buildings, resulting in less deposition of sand particles. The solar panel arrays were similar to the building arrays in most cases, but the deposition of sand particles on solar panels exerted a negative effect on energy utilization efficiency. Therefore, taking the optimal configuration of the settlement system into consideration, this study concludes that (1) brick arrays, which were proven effective in preventing sand particles, must be arranged in an upwind area; (2) solar panel arrays could accelerate the wind flow, so they are best to be arranged at the place where sand particles deposited easily; and (3) building arrays present a better arrangement in downwind areas.

Overview of the Measures and Techniques Used to Protect Traffic Lines against Shifting Sands in China

Shifting sands are one of the main contributors to desertification in China. This paper briefly reviews the measures and techniques which are used to protect traffic lines by stabilizing and fixing sands in the desert and desertification-affected arid and semi-arid areas in north China. We introduce the types and features of these measures and techniques, including mechanical, chemical, and biological measures, and outline how they have been applied in different areas and in different traffic lines over the past six decades, from 1950s to 2010s, taking the Baotou-Lanzhou railway, the Qinghai-Tibet railway, and the Tarim Desert highway as examples Mechanical measures such as erecting sand-retaining wind walls and placing straw checkerboards have proved to be very efficient for stabilizing shifting sands and protecting traffic lines that pass through the desert areas. Chemical measures are not widely used in the current sand fixing systems because of their high cost and potential pollution risks. Biological measures are preferred because they exhibit much better sand fixation performance and longer duration than the former two types of measures despite their relatively high cost. A combination of different measures is usually adopted in some areas to attain better sand-fixing effects. Stabilizing sand dune surfaces with mechanical measures or irrigation from underground water or river if available helps early recruitment of some drought-tolerant plants (xerophytes). We also point out the restrictions for existing sand-fixing measures and techniques and future research orientation. This review has implications for addressing eco-environmental issues associated with infrastructure construction that is part of the Belt and Road Initiative in desert and desertification-affected arid and semi-arid areas in the Mongolian Plateau.

Comparing straw checkerboards paving methods in deserts of China with sustainability indicators

The straw checkerboard sand barrier (SCSB) is widely used to fix sand and prevent desertification n China. In this paper, two methods of straw checkerboard (SC) paving are compared using sustainability indicators: the traditional method employing workers using straw and shovel, and the mechanized method using straw and a sand fixing vehicle. The paper describes the processes of the two different paving methods. Data regarding these two different methods of SC0020 paving were obtained from prior research experiments conducted by a sand-fixing vehicle prototype. The paper proceeds to use three sustainability indicators representing the three aspects of sustainable development. Using these indicators, data were compared to assess these two methods. The results show that the operational efficiency of the mechanized method is nearly 200 times higher than the traditional method, and that the total cost in the operational process can be reduced by about 7, 200 Yuan (about 1,145 USD) per hectare. The completion cycle of the break-even point (164 hectares) is 52.5 days in mechanized method, which is about one tenth of the traditional method. This not only indicates a clear advantage of performance and cost-effectiveness for the mechanized process over the traditional method, but also shows that this mechanized process can contribute to sustainable development for the region greatly because the preliminary work on degraded land and soil restoration can be completed in a significantly shorter period and the health conditions of a large number of manual workers can be improved.

Towards stopping land degradation in drylands: Water‐saving techniques for cultivating biocrusts in situ

AbstractIn recent years, inoculating sand surfaces with biocrust organisms has become one of the most promising biotechnological strategies for controlling and reversing land degradation in drylands. To fully exploit this biotechnology on a large scale in drylands, researchers must explore water‐saving techniques to incubate biocrusts in situ. To achieve this aim, we tested three methods—broadcasting dried cyanobacteria, spraying fresh cyanobacteria, and broadcasting natural biocrust fragments—to culture biocrusts in situ on the Tengger Desert in Northern China. The cover of incubated biocrust increased during the first 2 months after inoculation (from 6% to more than 20.0% in treatments using biocrust fragments); biocrust cover declined but persisted after 12 months of incubation (13.8% cover in the best treatment, natural cyanobacteria fragments). The cover of cyanobacteria was higher than the cover of lichen in our natural cyanobacteria‐lichen crust fragment treatment (NCL; p &lt; .05) after incubating for 12 months. We highlight that cyanobacteria should be selected for biocrust incubation during the initial stages of dryland restoration. Accumulated rainfall was positively related to the cover of incubated biocrust. However, wind speed and wind erosion intensity were both negatively related to the cover of incubated biocrust. In conclusion, broadcasting biocrust fragments is a rapid, efficient, and water‐saving biotechnique to cultivate biocrusts in situ. Actions to reduce wind speed and wind erosion, such as mechanical sand fixing, can help stabilize soils and improve crust cultivation.

Land use/land cover changes and its impact on ecosystem services in ecologically fragile zone: A case study of Zhangjiakou City, Hebei Province, China

Abstract Land use/land cover (LULC) changes are likely to become more frequent and intense as a result of anthropogenic activities and may significantly affect human welfare by modifying ecosystem services (ESs). Understanding the impact of LULC changes on ESs value and the interactions among ESs could result in improvements in current land use policies and provide a scientific basis for the formulation of new policies in ecologically fragile zones. A case study was conducted in Zhangjiakou City, which is considered a typical ecologically fragile mountainous area in China, to examine the effects of LULC changes on ESs value and the interactions among ESs, including carbon sequestration and oxygen production (CSOP), water yield (WY), soil conservation (SC), sand-fixing (SF), and agricultural production (AP) from 2000 to 2015. Our results showed that ESs in Zhangjiakou City benefited substantially from existing land use policies and their “win-win expectations.” There were dramatic changes in the LULC types over the study period, especially in forestland, grassland, and arable land, with a significant impact on ESs value. LULC changes resulted in a significant increase in ESs value (US$ 3147.44 million), with the maximum increase occurring in AP (US$ 2255.19 million). However, LULC significantly decreased the value of the WY by $61.91 million, which mainly resulted from the degradation of arable land, forestland, and grassland. Strong trade-off relationships between WY and SC, CSOP and SC, SC and SF, and SC and AP were observed in 2000. Trade-off relationships were markedly weaken by LULCCs but increased by human activities when related to AP. Finally, a new spatialization approach of AP was designed and quantitative method of trade-off index was improved based on economic value. These results could offer some suggestions for land space optimization and ecological construction in Zhangjiakou City as well as in the similar regions in China, and provide some scientifically basis on the research area of coordination development of multi-functions of land use or geographical functions.

Mechanical sand fixing is more beneficial than chemical sand fixing for artificial cyanobacteria crust colonization and development in a sand desert

The incubation of biological soil crusts (BSCs) can potentially determine a decrease in abiotic stress levels, which can then shift the state of the ecosystem and combat desertification due to their key ecological roles in drylands. Stabilized sand soil surface is the primary factor for natural and induced BSCs successful establishment in harsh dryland environments. Mechanical sand fixing, such as straw checkerboard barriers and chemical sand fixing are two effective ways to stabilized sandy soil surface. The impacts of these two sand fixing methods on artificial cyanobacteria colonization have not been frequently been compared in the field. In this study, five cyanobacteria, Anabaena sp., Nostoc sp., Phormidium sp., Scytonema sp. and Tolypothrix sp. were isolated and cultured. The straw checkerboard method was represented mechanical sand fixing and W-OH (modified water-borne polyurethane) method was used to test chemical sand fixing. Coverage, thickness and biomass of artificial cyanobacterial crust as well as wind erosion intensity and dust deposition were measured after 16 months of inoculation. Results show that the highest coverage, thickness and biomass of artificial cyanobacterial crust was in the straw checkerboard mechanical method, with cyanobacteria measuring higher than other treatments (p < 0.05) at 28.3%, 3.01 mm and 0.24 mg cm−2, respectively, and showed both positive relationships with dust deposition and herb coverage, but negatively with wind erosion intensity (p < 0.05). Thus, mechanical sand fixing was more beneficial to artificial cyanobacterial crust incubation in field conditions rather than chemical sand fixing, due to sustaining increase in dust deposition to sand surface stability. In addition, mechanical sand fixing uses lessees water than chemical sand fixing. Our results also indicated that annual herb coverage should be closely managed during the artificial cyanobacterial crust incubation in field conditions.

К синтаксономии псаммофитной растительности памятника природы «Дьяковский лес» (Саратовская область)

К синтаксономии псаммофитной растительности памятника природы «Дьяковский лес» (Саратовская область)

The motion rule of sand particles under control of the sand transportation engineering

In the desert and Gobi regions with strong wind and large sediment discharge, sand transporting engineering is more effective than sand blocking and sand fixing measures in sand prevention. This study uses the discrete phase model of 3D numerical simulation to study the motion trail, motion state and distribution rule of sand particles with different grain diameters when the included angle between the main shaft of the feather-row lateral transportation sand barrier and the wind direction changes, and conducts a comparison in combination with the wind tunnel test and the flow field rule of common sand barrier. According to the comparison, when wind-sand incoming flow passes through a feather-row sand barrier, sand particles slow down and deposit within the deceleration area under the resistance of the feather-row sand barrier, move along the transportation area formed by the transportation force, and accumulate as a ridge at the tail of the engineering. With increasing wind speed, the eolian erosion of the sand particles to the ground and the feather-row sand barrier is enhanced, and the sand transporting quantity and throw-over quantity of the feather-row sand barrier are both increased. When sand particles with different grain diameters bypass the feather-row sand barrier, the particle size of the infiltrating sands will increase with the included angle between the main shaft of the feather-row sand barrier and the wind direction. The obtained result demonstrates that, at a constant wind speed, the flow field formed is most suitable for the lateral transportation of the wind-drift flow when the included angle between the main shaft of the feather-row sand barrier lateral transportation engineering and the wind speed is less than or equal to 30

Analyzing the Sand-fixing Effect of Feldspathic Sandstone from the Texture Characteristics

The purpose of this research was aimed to study the sand fixing effect of feldspathic sandstone in Mu Us Sandy Land, to provide a scienticic basis for desertification control, soil and water conservation and development of farming there. Methods of mixing feldspathic sandstone and aeolian sandy soil according to 1: 0, 1: 1, 1: 2, 1: 5, and 0: 1 mass ratioes, the graded composition and characteristics were studied with laser particle size analyzer. The result showed that these features of sand-based, loosely structured, easy to wind erosion of aeolian sandy soil were changed before feldspathic sandstone and aeolian sandy soil compounding. The <0.05 mm particle mass increased with feldspathic sandstone mass increasing. The texture presented this kind of change from sand to sandy loam to loam to silt loam. The small particle size distribution, good homogeneity and other features of aeolian sandy soil were improved to a certain degree, and the particle size distribution became broad before feldspathic sandstone and aeolian sandy soil compounding. The particle grading was continuous, and the grading characteristic was good when m(F): m(S) was 1: 5(Cu was 54.71 and Cc was 2.54) or when m(F): m(S) was 1: 2(Cu was 76.21, Cc was 1.12). The conclusion is that feldspathic sandstone has sand-fixing effect in texture characteristics, which heightens with feldspathic sandstone mass increasing, and when the mass ratio of feldspathic sandstone: aeolian sandy soil is 1: 2 or 1: 5 which compound better.

One‐Step Synthesis of Biodegradable Polyurethane Prepolymer and Its Rapid Gelation Behavior at High Water Content

In this study, a very simple, scalable, and low‐cost one‐step recipe is presented for preparing a biodegradable polyurethane prepolymer composed of isocyanate terminated linear polyethylene glycol and isocyanate terminated four‐armed polycaprolactone. Then, the corresponding hydrogels are easily formed by mixing the prepolymer with water in few minutes. The resulting hydrogel shows excellent mechanical properties with high tensile strength (up to 233.6 KPa) and recorded elongation rate (5000%), while maintaining high water content (up to 91% mass ratio). Meanwhile, the maximum water retaining capacity of the hydrogel can be up to 40 times of polyurethane prepolymer (in mass), which is equal to 97.6% water content. In addition, the degradation properties of the obtained hydrogel are studied in detail. This study demonstrates a facile approach to prepare the hydrogel with both excellent mechanical properties and high water content, which marks it as a potential candidate for applications in agrological field, such as sand fixing in desertification control. image

Causes and controlling pattern of sand hazards at the Danghe Reservoir of Dunhuang in Northwest China

Sand hazards are serious at the Danghe Reservoir of Dunhuang, and efforts to control sand are ineffective because disaster-causing mechanisms are currently unclear. The source of sandy materials, dynamic environment of blown sand, and controlling measures of the reservoir area are investigated using different methods, such as granularity analyses, wind regime and sand transport field observation and analyses, sand drift potential calculation. Accordingly, the sandy materials are found to derive chiefly from the Mingsha Mountain on the north side of the reservoir area. In addition, sand grain in the range of 0.50-0.25 mm and 0.25-0.10 mm are dominant. The prevailing sand-moving wind originates from the N direction, accounting for 15.38% of the yearly total, which coincides in the same direction with sand source, thereby increasing the severity of sand hazards in the reservoir area. The yearly sand DP is 1386.59 VU, the yearly RDP is 567.31 VU, the yearly RDP/DP is 0.41, and the yearly RDD is 183.15°. In the windy season (mainly in summer), sand materials are blown by wind from north to south, and then blocked by the Danghe River. The sand materials then move with an approximate east-west trend into the river channel and produce sediment, thereby causing a disaster. We propose that the sand-controlling pattern of the Danghe Reservoir is dominated by sand blocking in the outer fringe and sand fixing in the inner fringe. Applying windbreak and sand fixation to control sandy material movement into the river channel plays an important role in retarding sedimentation and extending the useful life of the Danghe Reservoir.

A simple and fast formation of biodegradable poly(urethane-urea) hydrogel with high water content and good mechanical property

Abstract The synthesis of biodegradable hydrogels with both good mechanical properties and high water content is still a great challenge. In this study, a simple and scalable strategy for the preparation of a biodegradable polyurethane prepolymer composed of isocyanate terminated linear polyethylene glycol (L-PEG) and isocyanate terminated three-armed poly( l -lactic acid) (T-PLLA) is described. When mixed with water, the prepolymer forms a poly(urethane-urea) hydrogel in few minutes. The effect of the molecular weight and the feeding ratio of L-PEG and T-PLLA on the mechanical property of the poly(urethane-urea) hydrogel is discussed. The resulting hydrogel shows good mechanical properties with high tensile strength (up to 108 KPa) and recorded elongation rate (4500%), while maintaining high water content (up to 91% mass ratio). Meanwhile, the maximum water retaining capacity of the hydrogel can be up to 38 times of PU prepolymer (in mass), which is equal to 97.4% water content. Its degradation property is analyzed by the loss of tensile strength and cross section morphology through SEM with time. Such a low cost and biodegradable poly(urethane-urea) hydrogel, which combines fast hydrogel formation, high water content and good mechanical properties, might be used as potential candidates for applications in agrological field, such as sand fixing in desertification control.

Formation mechanism and suitable controlling pattern of sand hazards at Honglianghe River section of Qinghai–Tibet Railway

The sand hazards at Honglianghe River section of Qinghai–Tibet Railway are serious, and the effect of controlling measures is limited because the disaster-causing mechanism is currently unclear. The source of sandy materials, blown sand power environment, and controlling measures of Honglianghe River section were investigated by using methods such as field observation and analysis and indoor calculation to understand the sand hazard rules of Qinghai–Tibet Railway systematically. The sandy materials discovered are mainly from the sandy hill of the west side of the railway. In addition, the grain composition of sand with particle size in the range of 0.25–0.10 mm is given priority. Yearly sand-moving winds are usually from the N, NNW, and NW directions. The frequencies of these three wind groups accounted for 85.16 % of the yearly total. The most serious sand hazards were located at the NW direction of the railway. The yearly sand drift potential (DP) is 270.57 vector units (VU), the yearly resultant drift potential (RDP) is 247.27 VU, the yearly direction variability index (RDP/DP) is 0.91, and the yearly resultant drift direction is 162.84°. In windy dry season (during the colder half of the year), loose and broken sand materials are blown up by wind, forming wind–sand flow and movement, which are then blocked by the railway subgrade, and accumulate and thus cause disaster. We propose that the sand-controlling pattern of Qinghai–Tibet Railway is dominated by sand blocking and sand fixing, namely sand blocking in the outer fringe and sand fixing in the inner fringe, supplemented by sand transport and sand diversion, combined with vegetation. This pattern can be a significant reference to controlling sand hazards in other similar zones.