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1.
基于CT图像的土壤孔隙结构三维重建及水力学性质预测 总被引：6，自引：4，他引：2
为了更好地了解土壤孔隙结构对水分运动过程的影响机制,该文利用黄淮海平原原状潮土CT扫描图像,通过数字图像分析和计算机重建技术对孔隙结构进行三维重建,根据图像分析获得的孔隙大小分布和连通性等形态学参数建立了用于描述孔隙尺度结构特征对水分运动影响机制的网络模型,据此预测了样本尺度(样本体积为385.84cm3)的土壤水力学性质。结果表明,模型预测的水力学性质和实测值基本吻合,变化趋势基本一致,二者的决定系数达0.94以上。结果表明相关网络模型可以较好地模拟孔隙尺度的水分运动过程,可用于预测土壤的非饱和水力学性质。 相似文献
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土壤水力性质是研究非饱和带中水分和溶质运移的重要参数 ,可以用孔隙网络模型进行预测。通常采用的网络模型中的参数是任意指定的 ,无法真实反映土壤孔隙空间的形态特征。本文采用了一种基于孔隙形态学的网络模型来预测土壤的水力性质 ,即通过图像分析来直接测定孔隙的大小分布及其连通性 ,并将其结合到网络模型中 ,最大程度地再现了三维的土壤孔隙结构。本文根据河南封丘地区采集的砂壤土样本图像分析结果 ,采用形态学网络模型预测了其水力性质 ,同时也进一步评价了这种模型的优缺点及其应用前景。 相似文献
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基于CT数字图像的土壤孔隙分形特征研究 总被引：11，自引：0，他引：11
通过CT扫描获得了河南封丘地区3种不同质地潮土样本的高精度图像,利用数字图像分析方法识别出土壤孔隙及其轮廓线,然后用计盒法确定了表征土壤孔隙形态不规则性的分形维数.在此基础上,通过不同形式的分形模型预测了土壤水分特征曲线.结果表明,河南封丘地区不同质地潮土的孔隙分形维数(包括面积和轮廓线分维)差异不明显;预测水分特征曲线时,针对不同质地的土壤选择适宜的分形模型才能得到较好的模拟结果. 相似文献
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三峡山地不同坡位土壤的水分特征曲线及水力学性质 总被引：4，自引：2，他引：2
山地不同坡位的土壤水力学性质研究可为地表水文过程预测和坡地生态修复提供参考。通过采集三峡库区大老岭林区山地不同坡位的原状土样,测定饱和导水率、当量孔径、水分库容等水力学参数,利用V-G模型拟合土壤水分特征曲线,评价不同坡位土壤的渗透性能和持水能力。结果表明:坡顶土壤的入渗性能最好,平均饱和导水率为108.54 cm/d,其他坡位平均饱和导水率为34.81～47.56 cm/d。坡顶土壤的持水能力最差,吸力值从0增至100 kPa,含水量下降幅度最大(63.67%),其他坡位下降幅度在46.36%～52.07%。坡顶土壤大孔隙体积比最大可达20.95%,其他坡位在12.27%～16.58%。田间持水量库容占总库容的百分比以坡顶土壤最小(45.24%),其余在60.08%～65.33%。用V-G模型拟合土壤水分特征曲线,各样点决定系数R~2均大于0.95,拟合效果较好。饱和导水率与大孔隙体积比、砂粒含量呈正相关,与粉粒含量和黏粒含量呈负相关。V-G模型参数α与进气值相关,α值越小,持水能力越强。试验中α值与砂粒含量、大孔隙体积比呈正相关,与粉粒含量和黏粒含量呈负相关。砂粒和大孔隙越多,土壤持水性越差。参数n的取值影响拟合水分特征曲线的弯曲程度,n值越小,曲线越平缓。试验中n值与砂粒含量呈正相关,与粉粒含量呈负相关。砂粒含量越多,随吸力增大土壤排水越快。可见,山地坡面顶部土壤的持水能力最差,渗透能力最强,其他坡位差异不显著,V-G模型拟合的结果与实测结果一致。 相似文献
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水蚀风蚀交错带土壤剖面水力学性质变异 总被引：6，自引：0，他引：6
土壤剖面水力学性质的确定是土壤水分动态预测的基础。该文在水蚀风蚀交错区六道沟流域分别对居于坡中和坡上两块样地160 cm土层不同深度未扰动土壤的水分特征曲线进行了测定，将Van Genuchtens水分特征曲线模式与Mualem导水模式相结合，确定了两样地土壤剖面的水力学参数，对水力学参数在剖面的变化进行了分析。结果表明，土壤剖面饱和含水率、滞留含水率、进气吸力倒数和孔隙大小分布因子沿剖面变化不大，滞留含水率、进气吸力倒数属于中等程度变异，饱和含水率和孔隙大小分布指标属于弱变异，但经方差检验均不显著，说明该地区160 cm土壤剖面可以处理成均质剖面。 相似文献
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利用地统计学方法,选择江西省贵溪铜冶炼厂污染区,研究了表层水稻土中有效态重金属的空间变异特征和影响因素.分析表明,土壤有效态Cu、Cd、Pb为中等空间相关性,有效态Zn为弱空间相关性.有效态Cu、Cd分别与有效态Zn和有效态Pb呈显著相关,表现出复合污染的特征.土壤有效态重金属的空间分布有明显的各向异性.土壤有效态重金属的长轴方位角(西北-东南和东北-西南)与污染物的扩散方向(渠道和偏东风向)相近.随污染源距离的增加,土壤有效态Cu含量降低,而有效态Cd和Pb含量增加,有效态Zn含量在西北和东南两个方向上增加.相关分析表明,影响污染区水稻土中重金属有效态含量空间分布的主要因子是离污染源的距离和地形,其次是土壤的吸附能力(土壤SO42-含量)以及土壤pH,土壤有机质和土壤孔隙性的影响较小. 相似文献
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华北土石山区森林土壤大孔隙对土壤理化性质及根系的响应 总被引：2，自引：1，他引：1
土壤大孔隙是土壤水分、空气、化学物质及污染物优先运移的主要通道,对其形成机制的研究至关重要。以往对大孔隙的量化局限于传统方法,大孔隙三维形态特征的量化分析及其影响因素是目前大孔隙的研究重点。利用CT扫描及图像处理分析技术量化大孔隙三维形态特征参数,同时测定土壤基本理化性质及根长密度,分析土壤大孔隙三维特征对土壤理化性质及根系的响应。结果表明:土壤密度及土壤砂粒含量与大孔隙特征参数不存在相关关系;土壤有机质含量、土壤根长密度与大孔隙体积密度、大孔隙表面积密度、大孔隙数量密度呈现显著正相关关系,与大孔隙平均迂曲度呈现显著负相关关系。林木根系与土壤有机质对土壤大孔隙三维特征产生积极影响,表现为根系及土壤有机质含量越多,则大孔隙含量也越多,并具有更差的弯曲度。在今后对山地森林抚育管理、土壤水分运动机理及地下水污染评估等研究过程中不能忽略根系及土壤有机质差异对土壤大孔隙的重要影响。 相似文献
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我国主要变性土的微形态研究 总被引：2，自引：1，他引：2
本文研究了变性土三大土类黑粘土、浊粘土,艳粘土的微形态特征。通过大形态、微形态、超微形态观察和膨胀收缩试验揭示了变性土的孔隙、结构、粘粒的就地重新排列以及土壤垒结与土壤粘粒含量、粘粒种类以及土壤膨胀势之间的关系,其中福建浊粘土的微形态特征发育最明显。 相似文献
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适量砒砂岩改良风沙土的吸水和保水特性 总被引：8，自引：3，他引：5
该文研究了不同砒砂岩改良风沙土模式下的土壤入渗特征、饱和导水率和水分特征曲线,分析了不同模型对砒砂岩改良风沙土水分特征曲线的适用性和不同改良模式的土壤水力学特征,以期为评价砒砂岩改良风沙土水力学特性以及筛选合理改良模式提供科学依据。结果表明:砒砂岩可以有效降低风沙土的入渗率和饱和导水率,增加风沙土的饱和含水量和滞留含水量,增强风沙土的持水能力。VGM(m,n)模型可以拟合砒砂岩改良风沙土土壤水分特征曲线。同一改良模式下,土壤的入渗率、饱和导水率和饱和含水量随容重增大呈减小趋势;容积含水量在低吸力段随容重增大逐渐减小,在中高吸力段逐渐增大。砒砂岩和风沙土以25∶75比例混合的复配模式,可以有效改良风沙土的吸水和保水特性,可在实践中推广。 相似文献
11.
We investigated the possibility of inferring effective hydraulic properties of soil from the structure of the pore space. The aim was to identify structural properties, which are essential for water flow, so that physical experiments may be replaced by direct morphological measurements. The pore structure was investigated in three dimensions by serial sections through impregnated samples. The complex geometry of pore space was quantified in terms of two characteristics: pore-size distribution and pore connectivity. Only pores larger than 0.04 mm were considered. The results were used as input parameters for a pore-scale network model. The main desorption branch of the soil-water characteristic and the corresponding hydraulic conductivity function of the network model were calculated by numerical simulation. The simulation results, which are exclusively based on morphological investigations, were compared with independently measured results from a multi-step outflow experiment. This approach was demonstrated for two centrasting soil materials: the A and B horizons of a silty agricultural soil. The simulations were close to the experimental data, except for the absolute values of the hydraulic conductivity. The pore-size distribution and pore connectivity govern the shape of hydraulic functions and the applied morphometric methods are suitable for predicting essential characteristics of hydraulic soil properties. 相似文献
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Vegetated buffer zones (BZs) between arable fields and bodies of water are commonly established to reduce erosion and run‐off of particle‐bound nutrients. Functioning of a BZ depends on soil structure, as it is important for water infiltration. Therefore, it is vital to understand how varying management practices affect soils of BZs. We studied the structural and hydraulic properties of three differently managed BZs established in a boreal Vertic Stagnic Cambisol (clay, 51%). The three management practices for vegetation were as follows: natural with no treatment, harvested yearly and grazed by cattle. We used bulk density and macroporosity, together with a pore geometry index (air permeability per unit air‐filled porosity), to describe the soil structural properties. Hydraulic properties were measured at different length scales by means of an aggregate sorptivity test, saturated hydraulic conductivity of the core samples and field‐saturated hydraulic conductivity. Vegetation management markedly affected the physical properties in the top 5 cm of the soil. Properties were least favourable for infiltration at the grazed site, with the greatest bulk density, least macroporosity and hydraulic conductivity or greatest pore tortuosity. In general, spatial variation in zones with restricted and good hydraulic conductivity together with reduced aggregate sorptivity in the deeper horizons made the soil prone to preferential flow when initially dry. Prolonged wetness, on the other hand, reduced saturated hydraulic conductivity significantly, resulting in surface run‐off. Harvesting was considered the best management practice due to its inherent capacity for reducing the soil nutrient content and because it has minor implications for soil physical properties. 相似文献
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Soil hydraulic properties play a crucial role in simulating water flow and contaminant transport. Soil hydraulic properties are commonly measured using homogenized soil samples. However, soil structure has a significant effect on the soil ability to retain and to conduct water, particularly in aggregated soils. In order to determine the effect of soil homogenization on soil hydraulic properties and soil water transport, undisturbed soil samples were carefully collected. Five different soil structures were identified: Angular-blocky, Crumble, Angular-blocky (different soil texture), Granular, and subangular-blocky. The soil hydraulic properties were determined for undisturbed and homogenized soil samples for each soil structure. The soil hydraulic properties were used to model soil water transport using HYDRUS-1D.The homogenized soil samples showed a significant increase in wide pores (wCP) and a decrease in narrow pores (nCP). The wCP increased by 95.6, 141.2, 391.6, 3.9, 261.3%, and nCP decreased by 69.5, 10.5, 33.8, 72.7, and 39.3% for homogenized soil samples compared to undisturbed soil samples. The soil water retention curves exhibited a significant decrease in water holding capacity for homogenized soil samples compared with the undisturbed soil samples. The homogenized soil samples showed also a decrease in soil hydraulic conductivity. The simulated results showed that water movement and distribution were affected by soil homogenizing. Moreover, soil homogenizing affected soil hydraulic properties and soil water transport. However, field studies are being needed to find the effect of these differences on water, chemical, and pollutant transport under several scenarios. 相似文献
16.
生物炭对沙质土水分蒸发和导水率的影响 总被引：6，自引：0，他引：6
Biochar, as a kind of soil amendment, has important effects on soil water retention. In this research, 4 different kinds of biochars were used to investigate the influences of biochar addition on hydraulic properties and water evaporation in a sandy soil from Hebei Province, China. Biochar had strong absorption ability in the sandy soil. The ratio of water content in the biochar to that in the sandy soil was less than the corresponding ratio of porosity. Because of the different hydraulic properties between the sandy soil and the biochar, the saturated hydraulic conductivity of the sandy soil gradually decreased with the increasing biochar addition. The biochar with larger pore volume and average pore diameter had better water retention. More water was retained in the sandy soils when the biochar was added in a single layer, but not when the biochar was uniformly mixed with soil. Particle size of the added biochar had a significant influence on the hydraulic properties of the mixture of sand and biochar. Grinding the biochar into powder destroyed the pore structure, which simultaneously reduced the water absorption ability and hydraulic conductivity of the biochar. For this reason, adding biochar powder to the sandy soil would not decrease the water evaporation loss of the soil itself. 相似文献
17.
Use of an inverse method and geostatistics to estimate soil hydraulic conductivity for spatial variability analysis 总被引：2，自引：0，他引：2
Nunzio Romano 《Geoderma》1993,60(1-4):169-186
A field method for determining the soil hydraulic properties using a parameter estimation technique is presented. Input data for the inverse problem are soil-water potentials and soil-water contents measured at different soil depths and different times during a field transient drainage experiment. For the water retention function the parametric relation suggested by Van Genuchten was adopted. For the hydraulic conductivity function the relation proposed by Van Genuchten and the exponential relation were adopted.
With the proposed method soil hydraulic properties along a transect of a volcanic Vesuvian soil were determined using as boundary condition the unit gradient of total potential at the bottom of the soil profile. Geostatistics were used to describe the spatial variability of hydraulic conductivity characteristics of the soil here considered.
Finally, results obtained using this method were compared with those of the simplified method suggested by Sisson and Van Genuchten based on a unit gradient water flow model. 相似文献
18.
《土壤圈》2016,(2)
Biochar,as a kind of soil amendment,has important effects on soil water retention.In this research,4 different kinds of biochars were used to investigate their influences on hydraulic properties and water evaporation in a sandy soil from Hebei Province,China.Biochar had strong absorption ability in the sandy soil.The ratio of water content in the biochar to that in the sandy soil was less than the corresponding ratio of porosity.Because of the different hydraulic properties between the sandy soil and the biochar,the saturated hydraulic conductivity of the sandy soil gradually decreased with the increasing biochar addition.The biochar with larger pore volume and average pore diameter had better water retention.More water was retained in the sandy soil when the biochar was added in a single layer,but not when the biochar was uniformly mixed with soil.Particle size of the added biochar had a significant influence on the hydraulic properties of the mixture of sand and biochar.Grinding the biochar into powder destroyed the pore structure,which simultaneously reduced the water absorption ability and hydraulic conductivity of the biochar.For this reason,adding biochar powder to the sandy soil would not decrease the water evaporation loss of the soil itself. 相似文献