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1.
Improper cultivation practices are seriously degrading native forest ecosystems in northern Iran. Hence, the objectives of this study are to compare selected soil properties, runoff amount, erosion and also introducing equations to predict the runoff and soil erosion in three types of land use (forest, garden and cultivated). A simple portable rainfall simulator has been set in 90 random points to create experimental rainfall. Result showed that changes in natural forest led to a significant clay, organic carbon of soil, total N and antecedent soil moisture decrease and sand, pH and bulk density increasing. The rainfall runoff experiments indicate that runoff content of the natural forest soils was 35 % and respectively 38.45 % higher than the garden and cultivated land soils .This result could be related to the higher antecedent soil moisture in natural forest compared with the other land uses. According to the obtained results, garden soil erosion and cultivated land was 1.351 and respectively 1.587 times higher than the forest. The correlation matrix revealed that runoff content was positively correlated with antecedent soil moisture, bulk density and silt, and negatively with soil organic carbon, total N and sand. Also, soil organic carbon, total N, clay and sand showed negative correlation with soil erosion, while there is a positive correlation between erosion and silt, bulk density, pH and antecedent soil moisture. The results of multiple linear regression showed that runoff in forest, garden and cultivated land can be predicted with correlation coefficient of 0.637, 0.547 and 0.624, respectively. The correlation coefficients of 0.798, 0.628 and 0.560 in equations indicate their moderate potential in simulating soil erosion.  相似文献   

2.
A series of experiments to determine the direct emission of dust-sized particles from Gobi surfaces by clean wind (wind without sand), and the potential for aeolian abrasion of Gobi surfaces and beds of gravel and mobile sand to produce fine (<100 μm) and dust-sized (<10 μm, PM10) particles under sand-laden winds were conducted. Parent material was obtained from Gobi areas of the Ala Shan Plateau, the region with high dust emissions in arid China. The fine particles produced by aeolian processes were collected using sand traps and sieved the captured materials to exclude particles >100 μm in diameter and then PM10 by sedimentation was acquired. The Gobi surface provided most of the emitted fine particles during the initial dust emission processes, but subsequently, release of the clay coatings of particles by abrasion becomes the dominant source of fine materials. Under sand-laden winds, PM10 production rates produced by aeolian abrasion of Gobi surfaces ranged between 0.002 and 0.244% of blown materials. After removal of sand, silt, or clay with low resistance to erosion from the Gobi surfaces by the wind, the PM10 production rates caused by aeolian abrasion were similar to those from gravel and sand beds. The results also indicated that after the dust-sized particles with low resistance to erosion were removed, the production of dust-sized particles was unrelated to wind velocity. Under aeolian processes, Gobi deserts in this region therefore play a major role in dust emissions from arid and semiarid China.  相似文献   

3.
Soil particle-size distribution (PSD) is an important index for soil classification because it has large influences on soil hydrological characteristics, salinity, fertility, erodibility, nutrient content, swelling/shrinking, and degradation. We present a case study of the fractal characteristics of soil PSD and its relationship with soil properties of gravel-mulched fields in an arid area of northwestern China using single-fractal calculation. Particle size was unimodally distributed within the narrow range of 20–100 μm, with silt as the most common component. Horizontally, silt content was the highest, followed by sand and clay contents. Vertically, clay content increased with depth, while there were no obvious change rules for both silt and sand contents. The volume fractal dimension (D) of PSD ranged from 2.4307 to 2.5260, increased with the content of fine particles but decreased with the content of coarse particles. D was correlated positively with soil-water content and salt content and negatively with bulk density. The saturated soil-water content was strongly correlated negatively with silt content (p < 0.01) and positively with sand content (p < 0.01). The results indicate that D can be a potential indicator of the physical and chemical properties of soil and can also provide a theoretical basis and technical guidance for the effective use and management of the region.  相似文献   

4.
青木关岩溶槽谷流域不同土地利用类型土壤可蚀性分析   总被引：2，自引：0，他引：2  
陈英  魏兴萍  雷珊 《中国岩溶》2020,39(6):836-844
基于土壤实地采样和理化性质测试分析,采用EPIC模型K值计算方法,分析青木关岩溶槽谷流域的土壤理化性质、土壤可蚀性及其影响因子。结果发现:（1）青木关岩溶槽谷流域表层土壤（0~10 cm）可蚀性K值介于0.037 1~0.060 5之间,均值为0.048 5,中值为0.047 5,变异系数为10.71%,偏度和峰度值小于1;（2）表土机械组成中以粉粒含量为主,土壤质地属于粉壤土;有机质含量在13.98~52.24 g.kg-1之间,均值为29.20 g.kg-1;表土可蚀性K值与砂粒含量、有机碳含量呈极显著负相关,与粉粒含量呈极显著正相关,与黏粒含量呈负相关;（3）不同土地利用类型下的表土可蚀性K值以裸土地最大,为0.058 3,耕地次之,为0.053 4,其次为园地、荒草地和竹林,分别为0.048 3、0.047 8和0.046 9,针阔叶混交林最小,为0.0427,分别存在显著差异（P＜0.05）,变异系数介于2.7%～6.1%之间;受人类活动影响强烈的裸土地和耕地是本地区主要的泥沙策源地,恢复植被能有效提高土壤抗蚀能力;（4）不同土地利用类型土壤剖面K值均值为耕地（0.056 3）显著大于荒草地（0.051 6）与林地（0.048 1）（P＜0.05）,荒草地与林地K值间差异性不显著;K值剖面分布一致表现为0~35 cm相对较小且变化较大,土下35~60 cm随着深度的增加而增大。   相似文献   

5.
Soils containing expansive clays undergo swelling that can be both detrimental and beneficial in various applications. In the Arabian Gulf coastal region, natural heterogeneous soils containing clay and sand (tills, shales, and clayey sands) support most of the civil infrastructure systems. Likewise, mixes of clay and sand are used for local earthwork construction such as roads and landfills. A clear understanding of the swelling behaviour of such soils is pivotal at the outset of all construction projects. The main objective of this paper was to understand the evolution of swelling with increasing clay content in local soils. A theoretical framework for clay–sand soils was developed using phase relationships. Laboratory investigations comprised of mineralogical composition and geotechnical index properties of the clay and sand and consistency limits, swelling potential, and morphology of clay–sand mixes. Results indicated that soil consistency of mixes of a local expansive clay and an engineered sand depends on the weighted average of the constituents. Mixes with 10% clay through 40% clay capture the transition from a sand-like behaviour to a clay-like behaviour. Influenced by the initial conditions and soil matrix, the swelling potential of the investigated mixes correlated well with soil plasticity (SP(%) = 0.16 (I p)1.188). The parameters sand void ratio and clay–water ratio were found to better explain the behaviour of blended clay–sand soils.  相似文献   

6.
This paper provides a review of different particle size scales, size class terminology and particle size distribution (‘textural’) classification schemes which are widely used in sedimentology, geomorphology, soil science, aquatic ecology and civil engineering. It is concluded that a revised system of size class nomenclature, based on the Udden (1898) and Wentworth (1922) schemes, provides the most logical and consistent framework for use with sediments and a wide range of other particulate materials. A refined scheme is proposed which has five first‐order size classes (boulder, gravel, sand, silt and clay), each of which has five second‐order subdivisions with limits defined at one phi intervals. The scheme is simple and intuitively easy to understand. The paper also provides a review of previous schemes that have been proposed to describe and classify sediments on the basis of the proportions of gravel, sand and mud, or sand, silt and clay using trigons (also termed ternary diagrams). Many of these schemes do not have a logical basis and provide limited or uneven resolution. New gravel, sand and mud and sand, silt and clay classification systems are proposed that are both more logical and provide greater discriminatory power than previous schemes; they are therefore more suitable for use in environmental and forensic investigations. A new Microsoft Excel® program, freely available to download from http://www.kpal.co.uk , allows rapid classification of sediments based on the proportions of gravel, sand and mud and sand, silt and clay proportions and graphical comparison of the data for different sample groups.  相似文献   

7.
In highlands of semiarid Turkey, ecosystems have been significantly transformed through human actions, and today changes are taking place very rapidly, causing harmful consequences such as soil degradation. This paper examines two neighboring land use types in Indagi Mountain Pass, Cankiri, Turkey, to determine effects of the conversion of Blackpine (Pinus nigra Arn. subsp. pallasiana) plantation from grassland 40 years ago on soil organic carbon (SOC) and soil erodibility (USLE-K). For this purpose, a total of 302 disturbed and undisturbed soil samples were taken at irregular intervals from two sites and from two soil depths of 0–10 cm (D1) and 10–20 cm (D2). In terms of SOC, conversion did not make any statistical difference between grassland and plantation; however, there were statistically significant differences with soil depth within each land use, and SOC contents significantly decreased with the soil depth (P < 0.05) and mostly accumulated in D1. SOC values were 2.4 and 1.8% for grassland and 2.8 and 1.6% for plantation, respectively, at D1 and D2. USLE-K values also statistically differed significantly with the land use, and in contrast to the statistics of SOC, there was no change in USLE-K with the soil depth. Since USLE-K was estimated using SOC, hydraulic conductivity (HC) and soil textural composition––sand (S), silt (Si), and clay (C) contents of soils––as well as SOC did not change with the land use, we ascribed the changes of USLE-K with the land uses to the differences in the HC as strongly affected by the interactions between SOC and contents of S, Si, and C. On an average, the soil of the grassland (USLE-K = 0.161 t ha h ha−1 MJ−1 mm−1) was more erodible than those of the plantation (USLE-K = 0.126 t ha h ha−1 MJ−1 mm−1). Additionally, topographic factors, such as aspect and slope, were statistically effective on spatial distribution of the USLE-K and SOC.  相似文献   

8.
This paper applied the Revised Universal Soil Loss Equation (RUSLE), remote-sensing technique, and geographic information system (GIS) to map the soil erosion risk in Miyun Watershed, North China. The soil erosion parameters were evaluated in different ways: the R factor map was developed from the rainfall data, the K factor map was obtained from the soil map, the C factor map was generated based on a back propagation (BP) neural network method of Landsat ETM+ data with a correlation coefficient (r) of 0.929 to the field collected data, and a digital elevation model (DEM) with a spatial resolution of 30 m was derived from topographical map at the scale of 1:50,000 to develop the LS factor map. P factor map was assumed as 1 for the watershed because only a very small area has conservation practices. By integrating the six factor maps in GIS through pixel-based computing, the spatial distribution of soil loss in the upper watershed of Miyun reservoir was obtained by the RUSLE model. The results showed that the annual average soil loss for the upper watershed of Miyun reservoir was 9.86 t ha−1 ya−1 in 2005, and the area of 47.5 km2 (0.3%) experiences extremely severe erosion risk, which needs suitable conservation measures to be adopted on a priority basis. The spatial distribution of erosion risk classes was 66.88% very low, 21.90% low, 6.19% moderate, 2.90% severe, and 1.84% very severe. Among all counties and cities in the study area, Huairou County is in the extremely severe level of soil erosion risk, about 39.6% of land suffer from soil erosion, while Guyuan County in the very low level of soil erosion risk suffered from 17.79% of soil erosion in 2005. Therefore, the areas which are in the extremely severe level of soil erosion risk need immediate attention from soil conservation point of view.  相似文献   

9.
 This paper deals with the problem of increased heavy metal constituents in agricultural soils due to the expanded use of fertilizers and elevated atmospheric deposition. It discusses the extent of contamination in soil and establishes an environmental monitoring program in the chosen area of concern in the southern coastal region of Texas. Grain size, pH, and metals (Cu, Cd, Zn, Pb, Ni, Ba, As, Cr, Mn, and Fe) were determined in soils of the middle Rio Grande basin. The soils were mainly of sand texture and alkaline in character. Fine sand constituted the major proportion of the soil, and clay and silt ranged from 8–30% of the soil. Correlations of metal concentrations to grain size and iron contents were performed. Metals, except Cd and Pb, gave positive to negative relationships with decreases in grain size. Silt gave no relationship with metal content while clay and silt had a positive relationship. All these metals had a positive correlation with iron in the soil. The results indicate metals are associated with coarse sand, clay, and iron hydroxides surfaces of the soil. The comparison of metal content in soil of the middle Rio Grande basin with metals from other areas of the world suggests that it is relatively uncontaminated. Received: 14 December 1998 · Accepted: 19 Jaunuary 1999  相似文献   

10.
Vertical transport of selected polycyclic aromatic hydrocarbons (PAHs) in different particle-size fractions of sandy soils was investigated by simulation experiments in soil columns. Tested soil samples were fractionized into three particle-sizes including sand, coarse silt and fine silt (2,000–50, 50–20 and <20 μm). Rainfall simulations were conducted in artificially PAHs contaminated soil columns with 30 cm length and 5 cm diameter in 40 days. PAHs were extracted from soil samples and determined by high performance liquid chromatography (HPLC). Results showed that the residue level of PAHs in fine silt fraction reached 35.85 mg/kg, which was significantly higher than those in sand and coarse silt fraction (16.28 and 11.80 mg/kg, respectively), probably because PAHs in macroporous fractions were prone to volatilize or degrade compared with that in microporous fractions. Linear relationship between the residue levels of individual PAH (R PAHs) and the value of partition coefficient (log K oc) was regressed as R PAHs = 1.55 × log K oc − 5.86, R 2 = 0.91, n = 9. These results indicated that vertical transport of the mixed PAHs in soils were controlled both by the nature of PAHs (i.e. log K oc, molecular weight), soil particle size and soil organic contents, which could influence the transport of PAHs.  相似文献   

11.
Sixteen alluvial and terrace soils from Japan and Thailand were separated into six fractions ; an amorphous sesquioxide and combined organic matter fraction, crystalline sesquioxides, clay, silt, fine sand and coarse sand. Content of ten major and minor elements in these six fractions was analyzed; SiO2, A12O3, Fe2O3, MgO, CaO, K2O, TiO2, Rb2O and SrO were determined by X-ray fluorescence spectrometry, and Na2O was determined by neutron activation analysis. The clay, silt, fine sand and coarse sand mineralogy were estimated semi-quantitatively by X-ray diffraction methods.We propose three indices of geochemical maturity for the soils and test their usefulness as measures of the degree of weathering. Three concomitant factors are proposed to measure the relative resistate, hydrolyzate and oxidate nature of the major elements in the soils.  相似文献   

12.
Sand production by soil erosion in small watershed is a complex physical process. There are few physical models suitable to describe the characteristics of the intense erosion in domestic loess plateau. Introducing support vector machine (SVM) oriented to small sample data and possessing good extension property can be an effective approach to predict soil erosion because SVM has been applied in hydrological prediction to some extent. But there are no effective methods to select the rational parameters for SVM, which seriously limited the practical application of SVM. This paper explored the application of intelligence-based particle swarm optimization (PSO) algorithm in automatic selection of parameters for SVM, and proposed a prediction model by linking PSO and SVM for small sample data analysis. This method utilized the high efficiency optimization property and swarm paralleling property of PSO algorithm and the relatively strong learning and extending capacity of SVM. For an example of Huangfuchuan small watershed, its intensive fragmentation and intense erosion earn itself the name of “worst erosion in the world”. Using four characteristics selection algorithms of correlation feature selection, the primary affecting factors for soil erosion in this small watershed were determined to be the channel density, ravine area, sand rock proportion, and the total vegetation coverage. Based on the proposed PSO–SVM algorithm, the soil erosion modulus in the small watershed was predicted. The accuracy of the simulation and prediction was good, and the average error was 3.85%. The SVM predicting model was based on the monitoring data of sand production. The construction of the SVM erosion modulus prediction model for the small watershed comprehensively reflected the complex mechanism of soil erosion and sand production. It had certain advantage and relatively high practical value in small sample prediction in the discipline of soil erosion.  相似文献   

13.
In the rocky mountain area of North China, soil fertility has decreased with severe soil and water losses under various land uses. Land use has been proven to affect soil fertility spatial distribution patterns at larger scales. However, less information is available about these effects in field scale plots. Soil samples were collected at 2-m intervals by grid sampling from an area (18?×?18 m) within three land use types (poplar woodland, rotation cropland with peanut and sweet potato, and peach orchard). Soil properties including soil particle composition, soil organic matter, total nitrogen (TN), nitrate nitrogen (NO3 ?-N), total phosphorus (TP), and available phosphorus (AP) were measured for each sample. The spatial variability and spatial pattern of the soil properties were assessed for the three contrasting land use types. NH4 +-N, NO3 ?-N, and AP in the peach orchard and NO3 ?-N in the poplar woodland exhibited strong variation (coefficient of variance >100 %). Other properties showed moderate variations. With annual plowing and fertilization, soil properties in the rotation cropland had less variability and greater spatial autocorrelated ranges. The spatial dependences of sand content, TN, NO3 ?-N, and SWC in both the peach orchard and the rotation cropland were weaker than those in the poplar woodland, but the spatial dependences of TP and AP in the peach orchard were stronger than those in either the rotation cropland or the poplar woodland. Human activities such as plowing, fertilization, and harvesting had obvious effects on the spatial variability and spatial pattern of soil properties.  相似文献   

14.
The Menard pressuremeter test is a relatively expensive in situ test, which generates useful information about the strength and deformation properties of any soil and weak rock, which is carried out in some projects. On the other hand, the SPT test is a rather inexpensive, simple and typical in situ test used to determine the engineering properties of silt, clay, sand, and fine gravel which is utilised in almost all projects.

In this study SPT blow counts (N60) were correlated with pressuremeter modulus (EPMT) and limit pressure (PL) and empirical equations were proposed to estimate PL and EPMT from N60 in silty sand and silty clay soils separately. These tests have been conducted during subway geotechnical investigation in Mashhad, Iran.

Moreover, in order to verify these empirical equations, they were compared with similar equations that have been proposed by other researchers. These comparisons display that in all equations a linear relationship exists between N60 - EPMT and N60 - PL. However, the line slopes are different so it can be concluded the line slopes are related to soil type and geological condition of an area. Thus, for each area a separate empirical equation must be presented.  相似文献   


15.
青藏高原含砂砾石土壤导热率实验研究   总被引：4，自引：1，他引：3  
土壤导热率是土壤的基本物理参数之一,也是陆面模式的重要输入量,对研究土壤热传输、水热耦合运移有重要意义。青藏高原由于独特的地理环境备受学者关注,但目前常用的土壤水、热属性参数化方案仅仅考虑了沙土、粉土和黏土,就砂砾石重要性的认识还不足,很少有模式模拟砾石对青藏高原多年冻土和高寒草地的影响。采用便携式热导仪（KD2 Pro,DECAGON,美国）测量了青藏高原玛多和北麓河两地典型土壤在冻结和未冻结状态下不同水分条件时的土壤导热率,分析了砂砾石含量对土壤孔隙度的影响及冻结和未冻结状态下,不同水分条件下砂砾石含量对土壤导热率的影响。结果表明：当含水量高于某一阈值时,含水土壤冻结状态下的导热率高于未冻结状态下的导热率;土壤含水量对土壤导热率影响显著,导热率随着含水量的增加而增大,在含水量较小时变化更明显;砂砾石含量比重多的土壤孔隙度较小,且砂砾石含量越大的土壤在冻结状态下导热率高。以上结果表明,砂砾石对土壤导热率有显著影响,在将来的模式模拟研究中必须考虑砂砾石对土壤热属性的影响,进而提高土壤水热过程模拟的精度。  相似文献   

16.
Karst poljes in the Dinaric Mountains have a complex hydrological regime and high potential for crop production. Little information is available about soil organic carbon (SOC), total nitrogen (TN), carbon stocks (SOCS), and nitrogen stocks (TNS) in karst poljes located in the Dinaric area. The objective of this paper was to study the spatial distribution of SOC and TN in topsoil (ranged from 9 to 53 cm depth) and whole profile SOCS and TNS (ranged from 15 to 160 cm depth) in the Livno karst polje depression (Bosnia and Herzegovina) using kriging and co-kriging approaches. We used the following properties as co-variates: distance from hills (DFH), distance from the lake (DFL), sand, silt, and clay content, TN, SOC, SOCS, and TNS. We only used the properties that had a significant correlation with the estimated properties as co-variates. The results showed that soils in the study area had high average SOC (7.92%), TN (0.79%), SOCS (191.05 t ha?1), and TNS (17.91 t ha?1) values. Histosols had the highest SOCS and TNS and Arenosols the lowest. The experimental variogram of LogSOC and LogTN was best-fitted by the spherical model, while the exponential model was the most accurate for LogSOCS and LogTNS. The spatial dependence was moderate for all studied soil properties. The incorporation of auxiliary variables increased the precision of the estimations from 35.7% (SOC?×?TN) to 49.2% (TNS?×?SOCS).  相似文献   

17.
To prevent the leakage of pollutant liquids into groundwater and sublayers, the compacted fine-grained soils are commonly utilized as mineral liners or a sealing system constructed under municipal solid waste and other containment hazardous materials. This study presents the correlation equations of the compaction parameters required for construction of a mineral liner system. The determination of the characteristic compaction parameters, maximum dry unit weight (γ dmax) and optimum water content (w opt) requires considerable time and great effort. In this study, empirical models are described and examined to find which of the index properties correlate well with the compaction characteristics for estimating γ dmax and w opt of fine-grained soils at the standard compactive effort. The compaction data are correlated with different combinations of gravel content (G), sand content (S), fine-grained content (FC = clay + silt), plasticity index (I p), liquid limit (w L) and plastic limit (w P) by performing multilinear regression (MLR) analyses. The obtained correlations with statistical parameters are presented and compared with the previous studies. It is found that the maximum dry unit weight and optimum water content have a considerably good correlation with plastic limit in comparison with liquid limit and plasticity index.  相似文献   

18.
Siruvani watershed with a surface area of 205.54 km2 (20,554 hectare), forming a part of the Western Ghats in Attapady valley, Kerala, was chosen for testing RUSLE methodology in conjunction with remote sensing and GIS for soil loss prediction and identifying areas with high erosion potential. The RUSLE factors (R, K, LS, C and P) were computed from local rainfall, topographic, soil classification and remote sensing data. This study proved that the integration of soil erosion models with GIS and remote sensing is a simple and effective tool for mapping and quantifying areas and rates of soil erosion for the development of better soil conservation plans. The resultant map of annual soil erosion shows a maximum soil loss of 14.917 t h−1 year−1 and the computations suggest that about only 5.76% (1,184 hectares) of the area comes under the severe soil erosion zone followed by the high-erosion zone (11.50% of the total area). The dominant high soil erosion areas are located in the central and southern portion of the watershed and it is attributed to the shifting cultivation, and forest degradation along with the combined effect of K, LS and C factor. The RUSLE model in combination with GIS and remote sensing techniques also enables the assessment of pixel based soil erosion rate.  相似文献   

19.
张阳明  杨昌锐 《探矿工程》1999,(3):21-22,24
通过大量的碎石桩工程资料,分析了碎石桩法对杂填土,素填土和亚粘土,粉砂和轻亚粘土,粘土,淤泥质土和淤泥的加固效果。  相似文献   

20.
Using field surveys and laboratory analysis, soil physical and chemical properties were studied at a site exhibiting the reversal of desertification in Yanchi County of China’s Ningxia Hui autonomous region. The dominant soil particle size changed from coarse-fine sand to a combination of very fine sand and silt + clay, and corresponding levels of each soil nutrient increased. The content of coarse-fine sand (2–0.1 mm) was significantly and negatively correlated with soil nutrient contents, whereas nutrient contents were significantly and positively correlated with the contents of very fine sand (0.1–0.05 mm) and silt + clay (<0.05 mm). The increasingly fine soil texture and the nutrient enrichment both facilitated rehabilitation of desertified land. The silt + clay content contributed the most to the increasing soil nutrient contents, and thus appears to be the key factor in reversal of desertification. Soil nutrient concentrations in the bulk soil increased with increasing content of soil nutrients with different particle fractions, and there were significant positive correlations between them. The nutrients in all particle size classes jointly decided the effect of soil nutrient contents on the reversal process. Principal-components analysis (PCA) revealed that the soil quality tended to increase during the reversal process, and that nutrient factors were more significant than particle size (i.e., were the dominant factor that influenced soil quality). Available nutrients and soil organic matter (SOM) were the most important nutrient factors. Silt + clay were the most important particle factors.  相似文献   

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