Colloid facilitated contaminant transport in soil.

直到最近，人们还认为化学物质进入地下水的主要形式是溶解在土壤水中的化学物质。然而，近年来的研究表明，土壤中的无机和有机小颗粒具有相对的流动性，可以随着入渗水的迁移而迁移。这些胶体颗粒每克干燥颗粒具有很大的表面积（通常在100-1000 m^2/g的数量级）。理论上，胶体可能因此能够携带大量的吸收化学物质通过土壤。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运输的影响。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粒度组分具有更高的吸附化学物质的能力，并且胶体-化学反应具有强烈的时间依赖性。我们还发现，当土壤中同时存在强吸附农药（草甘膦）和磷时，这两种化学物质将竞争总吸附能力。在胶体流动性和土壤结构方面，通过对广岛县壤土的大规模测量，揭示了间歇性降雨过程中多种因素对胶体流动性的影响。灌溉水组成和土壤结构（未扰动或重新填充的土壤以及有或没有连续大孔隙的土壤）都有很大的影响。研究发现，含连续大孔隙的土壤中胶体的累积淋滤可以用抛物扩散型模型来描述。此外，我们还开发了可以描述扩散控制的胶体在结构性土壤中的运移的模型，该模型与我们的测量数据吻合得很好。

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.