Colloid facilitated contaminant transport in soil.

直到最近，人们还认为，化学物质向地下水的转移主要是以溶解在土壤水中的化学物质的形式发生的。然而，最近的研究表明，土壤中的无机和有机小颗粒是相对移动的，可以随入渗水迁移。这些胶体颗粒具有每克干颗粒的大表面积（通常在100-1000 m^2/g的数量级）。从理论上讲，胶体可以携带大量的吸附化学物质通过土壤.本研究的目的是探讨三个因素，胶体-化学相互作用，胶体流动性和土壤结构对胶体促进化学物质迁移的影响.关于胶体-化学相互作用，我们已经表明，具有高土壤表面积的土壤的小颗粒尺寸部分具有更高的吸附化学品的能力，并且胶体化学反应强烈地依赖于时间。此外，我们还发现，当一个强吸附农药（草甘膦）和磷存在于土壤中，这两种化学品将竞争的总吸附capacity.Concerning胶体流动性和土壤结构，一个大的测量程序从广岛县的壤土显示在间歇性降雨事件中的胶体流动性的几个因素的影响。灌溉水的组成和土壤结构（原状或重新包装的土壤，也有或没有连续的大孔土壤）的大的影响进行了观察。研究发现，含连续大孔隙土壤中累积胶体淋溶可用抛物线扩散模型描述。此外，我们开发的模型，可以描述扩散控制的胶体通过结构性土壤的运输，并同意与我们的测量数据。

Until recently, it was believed that the tranport of chemicals to the groundwater would happen mainly in the form of chemicals dissolved in the soil-water. However, recent studies indicate that small inorganic and organic particles in the soil are relatively mobile and can be transported with the infiltrating water. These colloidal particles have a large surface area per gram of dry particles (typically in the order of 100-1000 m^2/g). In theory, the colloids may therefore be able to carry significant amounts of sorbing chemicals with them through the soil.The purpose of this research is to investigate the effcet of three factors, colloid-chemical interactions, colloid mobility, and soil structure on colloid-facillitated transport of chemicals.Concerning colloid-chemical interactions, we have shown that the small particle size fractions of the soil with high soil surface area have higher capacity to adsorb chemicals and that the colloidal-chemical reactions are strongly time-dependent. Also we found that when both a strongly-sorbing pesticide (glyphosate) and phosphorus are present in the soil, these two chemicals will compete for the total sorption capacity.Concerning colloid mobility and soil structure, a large measurement program on a loamy soil from Hiroshima prefecture showed the effect of several factors on colloid mobility during intermittent rainfall events. Large effects of both irrigation water composition and of soil structure (undisturbed or repacked soils and also soil with or without continuous macropores) were obseved. We found that accumulated colloid leaching from soils containing continuous macropores could be described by a parabolic diffusion type model. Also we developed models that can describe diffusion-controlled colloid transport through structured soils and that agree well with our measured data.