含岩屑紫色土水分扩散规律

紫色土中存在的岩屑显著影响土壤水分扩散。以往研究主要集中在> 2 mm岩屑上而忽视了<2 mm岩屑的作用。因此,探讨>2 mm岩屑对紫色土水分扩散的影响基础上,明确<2 mm岩屑的作用对完善含岩屑紫色土水分扩散规律的研究具有重要的意义,从而为土壤水动力学模型的构建提供理论依据。以四川盆地紫色页岩发育的暗棕紫泥土和泥岩发育的红棕紫泥土为研究对象,设置3种岩屑粒径(0.25~2,2~5,5~10 mm)和4种岩屑含量(0,30%,50%,70%),利用水平土柱吸渗法测定含岩屑土壤湿润锋变化特征、水分扩散率D(θ)和土壤含水率θ,并拟合D(θ)、Boltzmann参数λ与θ之间的关系。结果表明:对于暗棕紫泥土,岩屑粒径为2~5 mm时,土壤湿润锋前进速率和D(θ)随岩屑含量增加呈先增加后降低再增加的趋势;岩屑粒径为0.25~2,5~10 mm时,土壤湿润锋前进速率和D(θ)随岩屑含量增加逐渐增加。对于红棕紫泥土,岩屑粒径为2~5,5~10 mm,随岩屑含量增加,70%岩屑含量的土壤D(θ)明显大于其余3个岩屑含量的土壤,而30%岩屑含量和50%岩屑含量土壤之间的D(θ)无显著差异,且土壤湿润锋前进速率均呈先增加后降低再增加的趋势;岩屑粒径为0.25~2 mm时,土壤湿润锋前进速率和D(θ)随岩屑含量增加逐渐增加。因此,随岩屑含量提高,土壤水分扩散速率整体呈现增加趋势;且泥岩发育的土壤水分扩散速率高于页岩发育的土壤。

Water Diffusion Law of Purple Soil Containing Rock Fragments

Rock fragments in purple soil can directly affect soil water diffusion. The past research mainly focused on the rock fragments with particle size > 2 mm, while the particle size of < 2 mm was ignored. Therefore, based on discussing the influence of the particle size > 2 mm on the water migration of purple soils, it is of great significance to clarify the influence of < 2 mm rock fragments on the moisture diffusion of purple soil containing rock fragments, thus providing theoretical basis for the construction of soil hydrodynamic model. Purple shale and mudstone in Sichuan basin and their developed soils(dark brown purple soil and red brown purple soil) were taken as research objects, three kinds of rock fragments particle sizes(0.25 ~ 2, 2 ~ 5, 5 ~ 10 mm) and four kinds of rock fragments contents(0, 30%, 50%,70%) were set. The horizontal soil column suction method was used to determine the progress of wet front of the soils containing rock fragments, the water diffusivity D(θ) and the soil moisture content θ, Fitting the relationship between D(θ), Boltzmann parameters λ and θ. The result showed that for dark brown purple soil, when the particle size of the rock fragment was 2 ~ 5 mm, with the increase of rock fragments contents, the advancing rate of soil wetting front and D(θ) both had a tendency of increasing first, then decreased and finally increased;while when the particle size of the rock fragment was 0.25 ~ 2, 5 ~ 10 mm, with the increase of rock fragments contents, the advancing rate of soil wetting front and D(θ) gradually increased. For red brown purple soil, when the size of rock fragment was 2 ~ 5, 5 ~ 10 mm, the D(θ) of 70% rock fragments content was obviously larger than that of the other three rock fragments content of soils. The D(θ) of 30% rock fragments contents and 50% rock fragments contents were not significantly different. The advancing rate of soil wetting front had a tendency of increasing first, then decreased and finally increased. While when the particle size of the rock fragments was 0.25 ~ 2 mm, with the increase of rock fragments contents, the advancing rate of soil wetting front and D(θ) gradually increased. Therefore, with the increase of rock fragments contents, the soil water migration rate showed an increasing trend as a whole, and the water migration rate of soil which was developed by mudstone was higher than that by shale.