This paper analyzed the water-retention mechanism of feldspathic sandstone （fine-（〈 1 mm diam.） and gravel-sized （2-3 cm diam.） in Mu Us Sandy Land, Northwest China. The objective of this study is to study the e...This paper analyzed the water-retention mechanism of feldspathic sandstone （fine-（〈 1 mm diam.） and gravel-sized （2-3 cm diam.） in Mu Us Sandy Land, Northwest China. The objective of this study is to study the effect of feldspathic sandstone amendment on water retention in sandy land. The results showed that as the proportion of fine feldspathic sandstone in the sandy land soil increased, the soil texture changed from sand to silt loam, the capillary po- rosity gradually increased from 26.3% to 44.9%, and the soil saturated hydraulic conductivity decreased from 7.10 ram/rain to 0.07 mm/min. Feldspathic sandstone gravel formed micro-reservoirs in the sandy land soil, playing the role of a ＇water absorbent＇ and ＇water retaining agent＇ in sandy land. Amendment with feldspathic sandstone can increase water retention in the arable layer of sandy land by 67%. This study provides a theoretical basis for the amelioration of sandy land on a large scale. It can be concluded that amendment with feldspathic sandstone can improve the physical properties of sandy land soil and increase soil water retention.展开更多
Stochastic approaches are useful to quantitatively describe transportbehavior over large temporal and spatial scales while accounting for the influence of small-scalevariabilities. Numerous solutions have been develop...Stochastic approaches are useful to quantitatively describe transportbehavior over large temporal and spatial scales while accounting for the influence of small-scalevariabilities. Numerous solutions have been developed for unsatu-rated soil water flow based on thelognormal distribution of soil hydraulic conductivity. To our knowledge, no available stochasticsolutions for unsaturated flow have been derived on the basis of the normal distribution ofhydraulic conductivity. In this paper, stochastic solutions were developed for unsaturated flow byassuming the normal distribution of saturated hydraulic conductivity (K_s). Under the assumptionthat soil hydraulic properties are second-order stationary, analytical expressions for capillarytension head variance (σ_h^2 ) and effective hydraulic conductivity (K_ii~*) in stratified soilswere derived using the perturbation method. The dependence of σ_h^2 and K_ii~* on soil variabilityand mean flow variables (the mean capillary tension head and its temporal and spatial gradients) andmean flow conditions (wetting and drying) were systematically analyzed. The calculated variance ofcapillary tension head with the analytical solution derived in this paper was compared with fieldexperimental data. The good agreement indicates that the analytical solution is applicable toevaluate the variance of capillary tension head of field soils with moderate variability.展开更多
基金Under the auspices of Key Direction Program of Chinese Academy of Science(No.KZCX2-YW-Q06-03)MajorState Basic Research Development Program of China(No.2009CB421103)+1 种基金National Natural Science Foundation of China(No.41001050)Major Science and Technology Program for Water Pollution Control and Treatment(No.2012ZX07201004)
文摘This paper analyzed the water-retention mechanism of feldspathic sandstone （fine-（〈 1 mm diam.） and gravel-sized （2-3 cm diam.） in Mu Us Sandy Land, Northwest China. The objective of this study is to study the effect of feldspathic sandstone amendment on water retention in sandy land. The results showed that as the proportion of fine feldspathic sandstone in the sandy land soil increased, the soil texture changed from sand to silt loam, the capillary po- rosity gradually increased from 26.3% to 44.9%, and the soil saturated hydraulic conductivity decreased from 7.10 ram/rain to 0.07 mm/min. Feldspathic sandstone gravel formed micro-reservoirs in the sandy land soil, playing the role of a ＇water absorbent＇ and ＇water retaining agent＇ in sandy land. Amendment with feldspathic sandstone can increase water retention in the arable layer of sandy land by 67%. This study provides a theoretical basis for the amelioration of sandy land on a large scale. It can be concluded that amendment with feldspathic sandstone can improve the physical properties of sandy land soil and increase soil water retention.
基金This work was supported by the National NaturaI Science Foundation of China(Grant Nos:59509007,59879028)the Major State Basic Research Development Program of China(Grant No:G1999045700)the Fok Ying Tung Education Foundation.(Grant No:71027)
文摘Stochastic approaches are useful to quantitatively describe transportbehavior over large temporal and spatial scales while accounting for the influence of small-scalevariabilities. Numerous solutions have been developed for unsatu-rated soil water flow based on thelognormal distribution of soil hydraulic conductivity. To our knowledge, no available stochasticsolutions for unsaturated flow have been derived on the basis of the normal distribution ofhydraulic conductivity. In this paper, stochastic solutions were developed for unsaturated flow byassuming the normal distribution of saturated hydraulic conductivity (K_s). Under the assumptionthat soil hydraulic properties are second-order stationary, analytical expressions for capillarytension head variance (σ_h^2 ) and effective hydraulic conductivity (K_ii~*) in stratified soilswere derived using the perturbation method. The dependence of σ_h^2 and K_ii~* on soil variabilityand mean flow variables (the mean capillary tension head and its temporal and spatial gradients) andmean flow conditions (wetting and drying) were systematically analyzed. The calculated variance ofcapillary tension head with the analytical solution derived in this paper was compared with fieldexperimental data. The good agreement indicates that the analytical solution is applicable toevaluate the variance of capillary tension head of field soils with moderate variability.
