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1.
Water repellency in oil contaminated sandy and clayey soils   总被引：3，自引：3，他引：0  
Two sites from a humid tropical environment were studied with respect to soil water repellency caused by hydrocarbon contamination. Samples were analyzed for water repellency (molarity ethanol droplet method), total petroleum hydrocarbons, acute toxicity (Microtox) and field capacity. At both sites, water absorption times were logarithmically related to the molarity ethanol drop value (R > 0.95). In a sandy soil collected from an old separation battery which had been bioremediated, field capacity was strongly related to hydrocarbon concentration (R = 0.998); and at 10,000 mg/kg the calculated field capacity was only 75 % of the baseline. Water repellency was related to hydrocarbon concentration asymptotically and plant growth limiting values (severity > 3.0) were observed at low concentrations (2,400 mg/kg), even though toxicity was at, or below background levels. Bioremediated soil at this site had hydrocarbon concentrations only 1,300 ppm above background, but had extreme water repellency (severity = 4.6–4.7). Soil water repellency was also measured in a clayey, organic rich floodable soil, in a multiple pipeline right-of-way colonized by water tolerant pasture and cattails. Water repellency was associated with total petroleum hydrocarbon concentration (R = 0.962), but was not related to field capacity or toxicity. In this low-lying site, the water repellency observed in the laboratory is probably not representative of field conditions: samples taken at the end of the ten week dry season (and only four days before the first rains) showed ample moisture (> 80 % field capacity).  相似文献   

2.
An experimental study was performed to investigate the effect of perlite and perlite–lime admixtures on classification, shear strength, and durability properties of an expansive soil containing smectite clay minerals. Two types of mixtures, namely soil–perlite and soil–perlite–lime, were prepared with different percentages of perlite and compacted with standard Proctor energy at their optimum water contents. Samples of 38 mm diameter and 76 mm height for durability tests and square samples of 60 mm edge for shear box test were taken and preserved until test time in a desiccator. Disturbed samples were also taken to determine liquid and plastic limits. The expansive soil shows behavior of fine sand and silt due to pozzolanic reactions in microstructure caused by addition of lime and perlite. Although apparent cohesion of treated soil decreased with increasing amount of perlite for both types of samples, perlite–lime-treated samples had higher apparent cohesion than only perlite-treated samples. Large increments in angle of shearing resistance were obtained with increasing usage of perlite. Samples stabilized with only perlite could not show enough durability at the durability tests based on volumetric stability and unconfined compression strength. However, samples stabilized with lime and more than 30 % perlite proved to have enough durability and shear strength.  相似文献   

3.
In many petroleum-producing regions, there are not adequate controls to prevent pipeline breaks and spills, and thus soil is frequently contaminated with petroleum hydrocarbons. Different petroleum oil compounds may produce negative impacts on soil fertility. In this study, four fresh crudes, a weathered petroleum, and oils from bioremediated and burned sites were investigated (specific gravities 0.83–1.27). Fourier transform infrared spectroscopy revealed three predominant polar functional groups to be more plentiful in the heavier crudes. The relative abundance of these groups was used to calculate an index that was directly correlated with specific gravity (R 2 = 0.9960) and the percent of asphaltene plus (polars + resins) fractions in the oil (R 2 = 0.9643). This index correlated exponentially to the water repellency caused by petroleum in an alluvial soil (R 2 = 0.9928). Furthermore, extra-heavy oil at a concentration of 10,000 ppm, the maximum allowable oil concentration in the soil that is within regulatory norms in many US states and other countries, and with a specific gravity >1.002, showed severe water repellency. This study presents an alternative for determining soil remediation criteria based on the API gravity of the oil rather than the C-range of the hydrocarbon mixtures, simplifying analytical methods and systematically studying the interaction between the kinds of petroleum mixtures and potential impacts to soil fertility.  相似文献   

4.
The chemical–biological stabilization technology has been employed in several successful studies using sugarcane cachasse as the organic amendment. However, in some petroleum-producing areas, there are no sugar mills nearby (which is the source of this material), and the cost of transport to the contaminated site is prohibitive. Therefore, water lily, which is considered a weedy plant in many tropical and subtropical areas, was evaluated as an alternative. In 3-month experiment, water lily was compared (with and without addition of molasses) with cachasse for the treatment of clayey sediment contaminated with > 6% extra-heavy crude oil. All treatments resulted in a reduction in the hydrocarbon concentration of 15–23%, without significant differences (P > 0.05). During this process, the pH was reduced to the 7–7.5 range and water repellency (molarity ethanol drop) to 3.5–3.6 M. Also, field capacity increased to 36.3–38.5% humidity, establishing adequate conditions for the development of vegetation at this site. Likewise, toxicity was reduced to practically null (Vibrio fischeri bioassay), and hydrocarbons in leachates were reduced to 3.4–4.3 mg/l, conditions adequate for the protection of groundwater and human health in rural areas. This study confirms that water lily is an adequate substitute for the application of this treatment method for hydrocarbon-contaminated sites that are far from sugar production areas.  相似文献   

5.
In the arid and semi-arid environments where the rainfall is limited and variable, fallow period soil moisture conservation using stubble is one of the ways of increasing the soil moisture required for crop sowing and development. However, the effectiveness of moisture conservation using stubble depends on the paddock management, soil water content, and rainfall characteristics. To assess the effect of stubble rate and amount of rainfall on the soil moisture conservation, a two-season field experiment was conducted using four stubble rates (0, 2, 4, 6 t/ha) and two water supply amounts. The soil water dynamics was also analysed using a validated Agricultural Production System Simulator (APSIM). In the relatively wet summer season with a high initial soil water content, the amount of water stored in the 2, 4, and 6 t/ha stubble rate treatment plots was higher than that of the bare plots by 10.4, 15.9, and 17.8 mm, respectively. However, in the summer season with a relatively high amount of in-season water input and low initial soil water content, the soil water storage was increased by 29.4, 35.6, and 43.0 mm, respectively. Comparing the results of the two seasons, the highest increase was observed for the 2 t/ha stubble rate. The amount of conserved soil moisture was found to be the highest when the soil profile water content at the start of the summer-fallow period is low and the amount of rain during the summer season is high. The good agreement between the measured and APSIM-simulated soil water contents (R 2 = 0.812), indicates that the model can be used to assess the soil water dynamics under a fallow condition. The APSIM-simulated soil water balance using the weather data of the past 100 years indicated that in a year with low start-of-fallow period soil water content, a 6 t/ha stubble rate can increase the end-of-fallow period soil moisture by up to 60 %.  相似文献   

6.
Polycyclic aromatic hydrocarbon (PAH) and nitrated PAH (NPAH) products are toxic. Thus, determination of their concentrations is of great interest to researchers of soil and water pollution control. In this work, soil samples, surface water samples, and groundwater samples were collected, and the concentrations of 16 priority PAHs and 15 NPAHs were determined using an HPLC-ultraviolet detector. Results showed that the total PAH concentrations ranged within 489.69–1,670.11 ng/g (average = 905.89 ng/g) in soil samples, 4.00–23.4 μg/l (average = 9.84 μg/l) in surface water samples, and 2.14–22.3 μg/l (average = 8.37 μg/l) in groundwater samples. The NPAH concentrations were one to two orders of magnitude lower than the PAH concentrations and ranged within 22.72–128.70 ng/g (average = 63.88 ng/g) in soil samples. 2-Nitropyrene and 6-nitrochrysene were the most abundant compounds, accounting for about 14.3 and 26.5 %, respectively. Source analysis revealed that most PAHs originated from coal combustion around the study area, whereas NPAH studies suggested that the primary emission of gasoline engines and daytime OH reactions were the dominant sources of these compounds.  相似文献   

7.
Soil–water characteristics are necessary for water quality monitoring, solute migration and plant growth. Soil–water characteristic curve (SWCC) is a relationship between suction and water content or degree of saturation. However, little information is available concerning the impacts of grazing exclusion management on soil–water characteristics. Here, the soil–water characteristics of grasslands, which were excluded grazing for 5 (GE5) and 15 years (GE15), were studied. The saturated hydraulic conductivity (K s), SWCC, particle composition, field capacity and some other indexes were determined. Results showed that the clay content and K s of grassland soil were higher for GE15 than GE5. For both treatments, in low suction condition (≤100 kPa), the water holding capacity of 0–10 cm soil was the best. Water holding capacity of topsoil decreased gradually with the increasing of suction, and it reached the strongest when the suction reached 600 kPa. In all soil water suction, the water holding capacity of subsoil was the weakest. The van Genuchten expression was applicable for most of the samples, except 20–30 cm of GE5 and 10–20 cm of GE15. Dual porosity equation was applicable for all the samples. The soil–water capability and soil structure of which was fenced for 15 years is superior to that of 5 years. This study suggests that the enclosure management improved the soil structure and soil–water capability.  相似文献   

8.
Laboratory tests were conducted on a reddish-brown lateritic soil treated with up to 12 % bagasse ash to assess its suitability in waste containment barriers applications. Soil samples were prepared using four compaction energies (i.e. reduced Proctor, standard Proctor, West African Standard or ‘intermediate’ and modified Proctor) at ?2, 0, 2 and 4 % moulding water content of the optimum moisture content (OMC). Index properties, hydraulic conductivity (k), volumetric shrinkage and unconfined compressive strength (UCS) tests were performed. Overall acceptable zones under which the material is suitable as a barrier material were obtained. Results recorded showed improved index properties; hydraulic conductivity and UCS with bagasse ash treatment up to 8 % at the OMC. Volumetric shrinkage strain increased with higher bagasse ash treatment. Based on the overall acceptable zone obtained, an 8 % optimal bagasse ash treatment of the natural lateritic soil makes it suitable for use in waste containment barrier application.  相似文献   

9.
Soil structural disturbance influences the downward flow of water that percolates deep enough to become aquifer recharge. Data from identical experiments in an undisturbed silt-loam soil and in an adjacent simulated waste trench composed of the same soil material, but disturbed, included (1) laboratory- and field-measured unsaturated hydraulic properties and (2) field-measured transient water content profiles through 24 h of ponded infiltration and 75 d of redistribution. In undisturbed soil, wetting fronts were highly diffuse above 2 m depth, and did not go much deeper than 2 m. Darcian analysis suggests an average recharge rate less than 2 mm/year. In disturbed soil, wetting fronts were sharp and initial infiltration slower; water moved slowly below 2 m without obvious impediment. Richards’ equation simulations with realistic conditions predicted sharp wetting fronts, as observed for disturbed soil. Such simulations were adequate for undisturbed soil only if started from a post-initial moisture distribution that included about 3 h of infiltration. These late-started simulations remained good, however, through the 76 d of data. Overall results suggest the net effect of soil disturbance, although it reduces preferential flow, may be to increase recharge by disrupting layer contrasts.  相似文献   

10.
This paper presents results of the influence of clod size and initial moisture condition on the shearing behavior of a clayey soil with a plasticity index of 22. The clods were divided into different size categories, and then two groups of samples were prepared; samples with large clods (LC = clod size less than 38 mm) and samples with small clods (SC = clod size less than 4.75 mm). Two initial moisture conditions were achieved using two different moisture tempering times of 0 and 14 days. All samples were compacted to the same density and moisture content (95 % of maximum dry density and 2 % dry of optimum moisture content). Triaxial compression tests, including constant water content unsaturated tests and backpressure saturated, isotropically consolidated, undrained compression tests were performed at different confining pressures. At 0-day tempering time, samples prepared using large clods were found to be stiffer and stronger than those prepared using small clods. However, at 14-day tempering time, the strength of both LC and SC samples was similar.  相似文献   

11.
Large-scale vegetation restoration in China’s Loess Plateau has been initiated by the central government to control soil and water losses since 1999. Knowledge of the spatio-temporal distribution of soil water storage (SWS) is critical to fully understand hydrological and ecological processes. This study analysed the temporal stability of the SWS pattern during the rainy season on a hillslope covered with Chinese pine (Pinus tabulaeformis Carr.). The soil water content in eight soil layers was obtained at 21 locations during the rainy season in 2014 and 2015. The results showed that the SWS at the 21 locations followed a normal distribution, which indicated moderate variability with the coefficients of variation ranging from 14 to 33%. The mean SWS was lowest in the middle slope. The spatial pattern of SWS displayed strong temporal stability, and the Spearman correlation coefficient ranged from 0.42 to 0.99 (p < 0.05). There were significant differences in the temporal stability of SWS among different soil layers (p < 0.01). The spatial patterns of SWS distribution showed small differences in different periods. The best representative locations of SWS were found at different soil depths. The maximum RMSE and MAE at 0–1.6 m soil depth for the rainy season were 4.27 and 3.54 mm, respectively. The best representative locations determined during a short period (13 days) can be used to estimate the mean SWS well for the same rainy season, but not for the next rainy season. Samples of SWS collected over a fortnight during the rainy season were able to capture the spatial patterns of soil moisture. Roots were the main factor affecting the temporal stability of SWS. Rainfall increased the temporal stability of the soil water distribution pattern. In conclusion, the SWS during the rainy season had a strong temporal stability on the forestland hillslope.  相似文献   

12.
The Tropical Rainfall Measuring Mission (TRMM) is a joint space mission between NASA and the Japan Aerospace Exploration Agency (JAXA) designed to monitor and study tropical rainfall. In this study, the daily rainfall from TRMM has been utilized to simulate the soil moisture content up to 30 cm vertical soil profile of at an interval depth of 15 cm by using the HYDRUS 1D numerical model for the three plots. The simulated soil moisture content using ground-based rainfall and TRMM-derived rainfall measurements indicate an agreeable goodness of fit between the both. The Nash–Sutcliffe efficiency using ground-based and TRMM-derived rainfall was found in the range of 0.90–0.68 and 0.70–0.40, respectively. The input data sensitivity analysis of precipitation combined with different irrigation treatment indicates a high dependency of soil moisture content with rainfall input. The overall analysis reveals that TRMM rainfall is promising for soil moisture prediction in absence of ground-based measurements of soil moisture.  相似文献   

13.
The critical area around an oasis where desertification occurs determines the ecological security and stability of the oasis. In this study, the soil quality in the critical area of desertification surrounding the Ejina Oasis was evaluated by using a soil quality index (SQI). The soil surface moisture content was related to vegetation cover; it remained high to a distance of 600 m from the oasis, decreased at distances of 600 to 1,700 m, and then gradually increased to a distance of 1,900 m. The sand content and soil bulk density gradually decreased to a distance of 300 m from the oasis; however, the silt and clay contents, soil pH, soil organic matter (SOM), and total and available nutrients increased away from the oasis. From 300 to 1,900 m, the sand content and soil bulk density increased; however, values of other soil properties decreased. Thus, a distance of 300 m from the edge of the oasis represents an obvious demarcation point for soil properties. SOM and the clay content were the key factors that determined soil quality. SQI increased from 0.284 at the edge of the oasis to 0.793 at 300 m, decreased to 0.262 at 1,400 m, and then decreased further to 0.142 at 1,900 m. SQI was lowest at distances of 1,400–1,900 m. The area beyond 300 m from the oasis was most vulnerable to desertification, and is thus the area where desertification control measures should be strengthened.  相似文献   

14.
Soil moisture and its variations are key factors for understanding hydrological processes, which are characterized by a high temporal variability at different scales. The study was conducted at three field stations in the desert regions of northwestern China, where soil moisture measurements with gravimetric method were used to characterize the temporal stability of soil moisture using various statistical parameters and an index of temporal stability (ITS). The soils are a gray–brown desert soil at the Linze station, an aeolian sandy soil at the Fukang station, and a brown desert soil at the Cele station. Soil textures are accordingly sandy loam at Linze and Cele, and loamy sand at Fukang. The dynamic variation in soil moisture depends strongly on the rainfall pattern (amount and frequency) in these desert ecosystems. Soil moisture content is low and significantly different among the three desert ecosystems, with the maximum at the Linze station (6.61 ± 2.08 %), followed by the Cele (4.83 ± 0.81 %) and Fukang (3.46 ± 0.47 %) stations. The temporal pattern exhibits high variability because soil moisture is characterized by low temporal stability and a high coefficient of variation (CV). The standard deviation, CV, and ITS increase significantly with increasing soil moisture. Soil moisture displays a skewed frequency distribution that follows a logarithmic function at lower soil moisture but a log-normal distribution at higher values.  相似文献   

15.
Developing countries face the challenge of growing their economy while reducing the negative environmental impacts of industry, thus requiring treatment technologies that are economical and effective. One recent technology developed in the tropical part of Mexico for the remediation of petroleum-contaminated soil was tested in this scale-up project at an industrial level, whereas previously it had only been tested at laboratory scale; 150 m3 of bentonitic mud, contaminated with weathered hydrocarbons (3.4°API) at ~50,000 ppm, was treated with 4 % Ca(OH)2, 4 % organic amendment, and a fine-root tropical grass. Hydrocarbons in soil and in leachates, as well as pH, and acute toxicity (Microtox) were monitored for 28.8 months. At the end of the study, basal respiration, root density, and earthworm toxicity were also measured. The hydrocarbon concentration in soil was reduced to 45 %, and toxicity was eliminated. Hydrocarbons in leachates were reduced to ~1 mg/l, safe for human consumption. The pH adjustment depended on low soil moisture and was stabilized at 7.1. Intense revegetation resulted in good root density, within 90 % of nearby uncontaminated soil under pasture. Basal respiration was increased to levels comparable to uncontaminated tropical soils with agricultural use, pasture and gallery forest. At an industrial scale, strict moisture control was necessary for good pH stabilization. By controlling these conditions and applying this novel treatment process, it was possible to transform a heavily contaminated geological material into a non-toxic, fertile, soil-like substrate capable of maintaining a complete vegetative cover and microbial activity comparable to similar soils in a tropical environment.  相似文献   

16.
Foundry sand, an industrial waste, was treated with up to 12 % cement kiln dust content at comparative energy levels of British standard light, West African standard or “intermediate” (WAS) and British standard heavy (BSH) efforts at molding water contents ?2, 0, 2, 4 and 6 % of optimum moisture content. Samples were extruded from the compaction molds and allowed to air dry in the laboratory in order to assess the effect of desiccation-induced shrinkage on the material for use as a hydraulic barrier in waste containment application. Results recorded show that volumetric shrinkage strain (VSS) values were large within the first 5 days of drying; VSS values increased with higher molding water content, water content relative to the optimum moisture content. VSS generally increased with higher initial degree of saturation for all compactive efforts, irrespective of the level of cement kiln dust (CKD) treatment. A compaction plane of acceptable zones for VSS based on the regulatory value is ≤4 %. The influence of CKD treatment generally showed a decrease in the desiccation-induced volumetric shrinkage strain with increasing CKD content. This is largely due to the pozzolanic input of CKD. Finally, only the BSH compactive effort gave successful results of volumetric shrinkage strain at CKD treatment content of between 4 and 8 %, while 12 % CKD content produced successful volumetric shrinkage strain results at WAS and BSH compactive effort, respectively.  相似文献   

17.
This paper investigated the geotechnical properties of smectite-rich shale, and its implications as foundation material. Ten expansive shale samples were collected from foundation materials at Akpugo in Nkanu West L.G.A. of Enugu State, southeast Nigeria. Samples were subjected to grading, Atterberg limits-cum-compaction tests, slake durability, specific gravity, permeability, undrained triaxial tests and x-ray diffraction scan. Fines and sand contents of the soil samples range from 51–97% and 3–49% respectively. Liquid limit, plastic limit and plasticity index have average values of 60.7, 19.1 and 43.3% respectively. Linear shrinkage and free swell showed average of 16.3% and 76%. These results are indicative of predominant clay soil with high plasticity, compressibility and water holding capacity. XRD scan established presence of smectite and illite clay minerals, confirming soil high plasticity, capable of causing instability in foundation soil. The shale achieved maximum dry density range between 1.79 and 1.94 kg/m3 at optimum moisture content range of 6.9–12.8%, indicating poor to fair foundation materials. The shale cohesion ranges from 15 to 30 kPa while the angle of friction ranges between 10° and 18°, signifying an average strength soil material. Samples slake durability index and specific gravity fall within 24–55% and 2.50–2.58 respectively, suggesting non-durable and weak soil. Permeability of the samples ranges between 7.36 ×10?6 and 4.77 ×10?8 cm/s which suggested low drainage capable of causing water-log at sites. Therefore, the shale could be generally classified as poor to fair foundation material, which on moisture influx experience reduction in strength due to deterioration of its constituent minerals, especially clay and cement materials during the lifespan of engineering structures. Authors therefore recommend modification of foundation soil, appropriate foundation design and good drainage control as ways of improving stability of engineering structures underlain by expansive shale.  相似文献   

18.
The Eocene rock units of the Qadirpur field, Central Indus Basin (Pakistan), are investigated petrophysically for their detailed reservoir characterization. The different petrophysical parameters determined include the following: true resistivity, shale volume, total porosity, effective porosity, density and neutron porosity, water and hydrocarbon saturation, bulk volume of water, lithology, gas effect, P-wave velocity, movable hydrocarbon index and irreducible water saturation and integrated with different cross-plots. The Eocene reservoirs are excellent with high effective porosity (2–32 %) and hydrocarbon saturation (10–93 %). Among these, the Sui Upper Limestone is an overall a poor reservoir; however, it has some hydrocarbon-rich intervals with high effective porosity and better net pay. All the net pay zones identified show low and variable shale volume (5–30 %). The secondary porosity has added to the total and effective porosities in these reservoirs. The main contributors to the porosity are the chalky, intercrystalline and vuggy/fracture types. The thickness of the reservoirs zones ranges from 4.5 to 62 m. These reservoirs are gas-producing carbonates with almost irreducible water saturation (0.002–0.01) and are likely to produce water-free hydrocarbons. The lower values of moveable hydrocarbon index (0.07–0.9) show that the hydrocarbons are moveable spontaneously to the well bore. The proposed correlation model shows that the reservoirs have an inclined geometry and are a part of an anticlinal trap.  相似文献   

19.
Active microwave has a huge potential in the estimation of soil moisture especially over large areas where the meteorological observations are seldom. The large contrast in dielectric constant between different types of soil is considered as the main factor for measuring the moisture content. This study is aimed at the extraction of soil moisture over the areas of Bukit Antarabangsa, Malaysia using active microwave remote sensing technique in order to examine the impact of moisture content dynamically on landslides occurrence, which have been a basic challenge that threaten Bukit Antarabangsa area, particularly in falling of monsoon seasons. This study addressed a specific event that took place in 6 December 2008 due to a very high level of precipitation that resulted in a raise in ground water table causing the occurrence of landslide. One Radarsat-1 image acquired in July 2008 before the landslide was used for generating the moisture content map. The resultant moisture content map showed a reasonable distribution of the moisture concentrated over the forest areas which has previous records landslides. Moreover, it was found that the previous landslide events were within the high moisture zone indicating the presence of high moisture content. Subsequently, three moisture maps were extracted from Landsat-7 ETM+, which were then used for validation process. A statistically based validation technique was used by calculating area under the curve that correlates the high moisture values of three images. In order to validate the Landsat-7 ETM+ moisture content, monthly rainfall data was plotted against the high moisture values derived from three Landsat-7 images. The validation result indicated an acceptable compatibility. The spatial relation between high moisture areas in Landsat-7 ETM+ images along the year resulted in a good fitting in the high–low moisture distribution areas with sensitivity ranged of 60–70 %. Finally, the moisture content map generated by Radarsat-1 was validated using a landslide inventory map. The resultant validation produced an area under curve of 0.704 (70 %).  相似文献   

20.
The distribution of soil moisture in arid and semiarid regions is a major environmental factor and is regulated by regional topography, vegetation and soil texture. Here, we present the results of a study of the spatial distribution characteristics of soil moisture in the Mu Us Sandy Land, which is the transitional area between the northwestern deserts and the Chinese Loess Plateau, in North China. Samples were taken from holes drilled to a depth of 4 m in 52 different microtopographic positions on different types of dune (bare dunes, shrub-covered dunes and tree-covered dunes). The sites were located in the northwestern margin, the central region and the southeastern margin. All samples were analyzed for moisture content and grain size distribution. The results show that: (1) for the same type of dune, the soil moisture content varies in different microtopographic positions. The soil moisture content on windward slopes is greater than on leeward slopes in the shrub-covered dunes and the tree-covered dunes, while this is the case in only some of the bare migratory sand dunes. In addition, the soil moisture content on leeward slopes is greater than on the corresponding windward slope. (2) The vegetation type and density have a large influence on the moisture content of sandy soils; specifically, the presence of shrubs and trees significantly affects the soil moisture content of windward and leeward slopes and the inter-dune lowland. (3) Soil moisture content is positively correlated with the clay and silt content of sandy soils. From northwest to southeast across the Mu Us Sandy Land, the silt and clay content increases gradually; however, in the case of dunes covered with planted trees, a peak in the content of fine-grained material occurs in the central region, while for shrub-covered sand dunes, the peak occurs in the southeastern margin. In addition, the correlation between soil moisture and soil grain size distribution of the three types of dunes varies from northwest to southeast. (4) The proportion of fine-grained material and the correlation between the content of fine-grained material and soil moisture are the two main factors influencing the soil moisture distribution of the different types of dune. A soil moisture concentration index can be used as a rough indicator of the distribution characteristics of soil moisture.  相似文献   

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