2000 Fiscal Year Final Research Report Summary
Colloid facilitated contaminant transport in soil.
| Project/Area Number |
11650562
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Civil and environmental engineering
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
KOMATSU Toshiko Faculty of Engineering, HIROSHIMA UNIVERSITY, Associate Professor., 工学部, 助教授 (80034396)
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| Co-Investigator(Kenkyū-buntansha) |
OZAKI Noriatsu Faculty of Engineering, HIROSHIMA UNIVERSITY, Research Associate., 工学部, 助手 (50294541)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Soil colloid / Soil and groundwater pollution / Undisturbed soil / macropore / Pesticide adsorption / Parabolic diffusion model / Colloid Mobilization Index / Phosphorus leaching |
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| Research Abstract |
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.
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