|Budget Amount *help
¥3,200,000 (Direct Cost : ¥3,200,000)
Fiscal Year 1998 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1997 : ¥2,700,000 (Direct Cost : ¥2,700,000)
The purpose of this study is to analyze the infiltration process of the diluted pesticide into the soil through some laboratory experiments. The actual paddy soil was chosen for the experiments because of high frequency and amount of pesticide for weed control in Japan. The repacked soil column was used for the experiments to observe the hydrodynamic dispersion and transport of the chemical contents without some tortuosity related influences or non-uniformity in terms of hydraulic conductivity associated with heterogeneity in the soil.
A widely used agricultural pesticide, MCP soda salt, was chosen as the testing chemical from the reason of its low cost, chemical stability, and easiness in chromatographic analysis. Main content is 19.5% concentration of sodium 2-methyl-4-chlorophenoxyacetate hydrate. 200-240 grams of MCP diluted by 70-100 liters of water is commonly applied to 100 m^2 of the land surface. In this study, 1000 ppm was adopted to obtain a definite result under the actual condition. Some inhibitors in the soil was recognized using hexane as the extracting solvent. Sampling time periods were 0.5, 1.0, 2.0, 3.0, 126.96.36.199 hours along with the four different depths of 6.3, 16.3, 26.3, 36.3cm.
The results shows the pesticide dispersed to entire soil column shortly after the chemical application for the case of very low density. However, for the case of high concentration above 10% (100 ppm), several hours were needed to measure at every depth point. Some parameters in the BTC (Break Trough Curve) added to the convection-dispersion equation were presented as the variables for estimating the time to drain the pesticide through the paddy soil.