透气隔水埋体对土壤水分入渗与溶质运移的影响

为分析透气隔水(弱透水)埋体促进水分入渗与溶质运移功效,开展了不同容重(1.40,1.45,1.50,1.60 g/cm~3)透气隔水(弱透水)埋体的一维垂直土柱入渗试验,分析了不同容重的透气隔水(弱透水)埋体对土壤水分入渗与溶质分布的影响。结果表明,透气隔水(弱透水)埋体能够增加土壤累积入渗量,推动湿润锋运移,在一定范围内,随着透气隔水(弱透水)埋体容重增加,湿润锋推进速度与土壤入渗率均增加。600 min时,土壤累积入渗量相对增加7.42%～29.17%,湿润锋深度达到27 cm,入渗时间相对减少26.97%～64.27%。相比于对照组,不同容重的透气隔水(弱透水)埋体均能降低溶质向深层土壤迁移数量。Philip模型和代数模型均能描述透气隔水(弱透水)埋体土壤水分入渗过程,且Philip模型中吸渗率S和代数模型中综合形状系数α均与透气隔水(弱透水)埋体内外容重比呈正相关关系。研究结果表明透气隔水(弱透水)埋体能够通过改变上层土壤吸力分布提高水分入渗能力与溶质传输效率,实现对城市雨水径流调控和净化。     

溶质施加方式对土壤溶质迁移的影响

通过室内均质土柱试验 ,对不同灌水处理土壤中表施和灌施溶质的迁移规律进行了研究。结果表明 ,溶质施加方式和灌水频率对溶质迁移影响较大。次灌水量较大时 ,表施和灌施条件下溶质分布差异显著 ;当次灌水量很小且灌水非常频繁时 (如 6mm/ d) ,表施和灌施土壤中溶质 (NO- 3)分布差异不大。     

土壤结构组成对K+运移障碍因子的定量研究

With six packed columns composed of <1 μm and 5 μm~0.25 mm fractions from an Eum-Orthic Anthrosol (Columns 1~6) and one column of the Eum-Orthic Anthrosol (Column 7), K⁺ transport experiments under the condition of saturated steady water flow were conducted to qualify the effects of soil texture composition on the retardation factor (R) of K⁺ transport. The results showed that the retardation factor of K⁺ transport in the tested soil columns greatly increased with increasing clay contents. In an attempt to use pedo-transfer function (PTF) approach in the solute transport study, a preliminary PTF was established through the six packed columns (Columns 1~6) with soil basic data including soil bulk density, volumetric water content and clay content to predict the retardation factor, and proved valid by the satisfactory prediction of R in Column 7.     

地下滴灌土壤水运动和溶质运移的数学模型及验证

以非饱和土壤水运动理论和多孔介质中溶质运移的对流－弥散理论为基础，建立了地下滴灌条件下描述地埋点源土壤水运动和溶质运移的数学模型。模型中对滴头边界进行了简化，并对其可行性进行了检验。模拟计算结果得到室内试验资料验证。该模型可用来描述地下滴灌土壤水、肥运动和分布规律，以便为地下滴灌系统的合理设计提供理论依据。     

Column Holdup Formula of Soil Solute Transport

The shortcomings of the present two formulae for describing column holdup are analyzed and deductions are made to find a new formula. The column holdup, Hw, described by the new formula is dimensional,and related to soil solute transport kinesis and column physical properties. Compared with the other two column holdups, Hw is feasible to describe dimensional column holdup during solute transport process. The relationships between Hw and retardation factor, R, in different solute transport boundary conditions are established.     

NaCl胁迫对藜幼苗叶片渗透调节物质和保护酶的影响

[目的]研究不同浓度NaCl胁迫对藜叶片中渗透调节物质和保护酶活性的影响,以探讨藜的耐盐机理,为藜的人工栽培及推广提供理论依据。[方法]待藜幼苗长到4叶期时,用0%、0.6%、1.2%、1.8%NaCl溶液进行根部胁迫处理,分别于处理0、1、3、5、7 d后从藜幼苗上部取第3～5片功能叶片进行各项生理指标的测定。[结果]在0.6%NaCl胁迫下,渗透调节物质（可溶糖、脯氨酸和可溶性蛋白质）含量和保护酶（SOD、POD和CAT）活性都是缓慢增加的,丙二醛含量增加不大,膜脂过氧化水平低。在1.2%、1.8%NaCl胁迫下,渗透调节物质（可溶性糖、脯氨酸和可溶性蛋白质）含量随胁迫时间的延长而增加,SOD、POD、CAT活性随胁迫时间的延长先升高后降低,丙二醛含量显著提高,膜脂过氧化水平增大。[结论]藜可以通过渗透调节物质增加和保护酶活性增大来对适度的盐胁迫有一定的适应性,但高浓度、长时间的盐胁迫会对藜造成严重损伤。     

考虑水迁移率动态变化改进土壤溶质地表流失模型

农田土壤溶质的地表径流流失是农业面源污染的重要组成部分,为了更加有效预测和控制农田土壤溶质的流失,该文将水迁移率考虑为随土壤侵蚀变化而变化的函数,并修改Hydrus-1D代码数值求解土壤溶质的地表径流浓度值。利用两组已经发表的试验数据对改进的模型进行校验,研究结果表明该文模拟值与观测数据的相关系数r≥0.81,残差绝对均值和均方根差与原模型的模拟值相比,分别平均减少了35.42和60.77 mg/L,该文改进的模型能更好地模拟土壤溶质的地表径流流失规律。该文的研究成果将为实际预防和控制农业面源污染提供参考。     

Solute transport characteristics of a deep soil profile in the Loess Plateau,China

Understanding solute transport behaviors of deep soil profile in the Loess Plateau is helpful for ecological construction and agricultural production improvement. In this study, solute transport processes of a deep soil profile were measured by a conservative tracer experiment using 25 undisturbed soil cores(20 cm long and 7 cm diameter for each) continuously sampled from the surface downward to the depth of 500 cm in the Loess Plateau of China. The solute transport breakthrough curves(BTCs) were analyzed in terms of the convection-dispersion equation(CDE) and the mobile-immobile model(MIM). Average pore-water velocity and dispersion coefficient(or effective dispersion coefficient) were calculated using the CDE and MIM. Basic soil properties and water infiltration parameters were also determined to explore their influence on the solute transport parameters. Both pore-water velocity and dispersion coefficient(or effective dispersion coefficient) generally decreased with increasing depth, and the dispersivity fluctuated along the soil profile. There was a good linear correlation between log-transformed pore-water velocity and dispersion coefficient, with a slope of about 1.0 and an average dispersivity of 0.25 for the entire soil profile. Generally speaking, the soil was more homogeneous along the soil profile. Our results also show that hydrodynamic dispersion is the dominant mechanism of solute transport of loess soils in the study area.     

土壤溶质迁移的指数函数模型

边界层方法是描述土壤溶质迁移的简单方法,通过边界层距离与时间的关系可以估计溶质迁移参数。基于边界层方法,研究了土壤溶质迁移的数学模拟及相应参数估计问题。假定土壤溶质浓度剖面为指数函数,得到了描述溶质浓度分布的指数函数模型。各参数对边界层距离的影响分析表明,应选取较小的孔隙水流速度、短历时推求土壤溶质迁移参数;对不同模型预测土壤溶质分布进行比较,结果表明,在短距离处指数型解与精确解的误差比其它都要小。误差分析表明了指数函数模型的有效性和实用性。     

土壤溶质迁移的高次幂函数近似解析模型

为了利用解析模型模拟土壤溶质迁移过程、估计土壤溶质迁移参数,在假定土壤溶质质量浓度分布为n次幂函数的基础上,结合边界层方法,将描述土壤溶质质量浓度分布的低次幂函数进一步推广,得到土壤溶质迁移的n次幂函数近似解析模型.在2个时刻(t=360,720 min)、较大距离(120~450 cm)时,利用不同次幂函数模型对溶质迁移过程进行比较分析,模拟结果表明孔隙水流速度较小(v=0.01 cm/min)时,在短历时(t=360 min)、长距离(x>50 cm)处,六次幂边界层解与其他次幂边界层解相比具有较高精确度;对边界层距离公式受各参数的影响进行模拟计算,分析结果表明:较小的孔隙水流速度(v≤0.01 cm/min)对边界层距离影响甚小;基于较小土壤孔隙水流速(v=0.01 cm/min)及测量仪器的不同灵敏度,利用不同次幂边界层距离公式对土壤溶质迁移参数进行数值计算比较及误差分析,结果表明用较高灵敏度的仪器进行测量,结合六次幂的边界层距离公式可准确地推求土壤溶质迁移参数弥散系数D及延迟因子R.