| Summary: | 碩士 === 國立臺灣大學 === 環境工程學研究所 === 95 === Farmers in Taiwan often open-burn their agriculture wastes on-site after harvesting in the autumn. This kind of burning practices produces a large amount of black carbon, which will be accumulated in the soils. The purpose of this study lies in estimating the black carbon amount of some areas in Taiwan, and its influence to the availability of pesticides in farmland soils.
This study developed the analytical method for the content of black carbon in soils by using weak acid to remove the carbonate in the soil, heating soil under 375 ℃ and sufficient air, and then measuring the carbon content of the left materials by element analysis. Black carbon was isolated by using chemical pretreatment and density fractionation by isolating the material with density between 1.8 and 2.05 g/cm3. Black carbon which we made by burning the straw was also investigated for comparison.
Diuron sorption by black carbon in aqueous solution was investigated by batch equilibration technology, extracting diuron by using solid-phase microextraction (SPME) method and measuring the concentration of the diuron aqueous solution by gas chromatograph equipped with electron capture detector.
The black carbon that isolated by density fractionation is from Hsienshi of Changhua county. The surface area is 14 m2/g , and the content of carbon is 17%. Surface area of the black carbon that produced by burned straw is 78 m2/g and the content of carbon is 14%.
A dual-mode model was used to simulate the adsorption of diuron on soil of Hsienshi of Changhua county, assuming that the adsorption of soil is contributed by sorption into organic matter and adsorption on black carbon. It is found that the amount of diuron adsorbed on the black carbon accounts for a large fraction of the amount sorbed on soil than organic matter does in low diuron concentration. Black carbon account for 64% of soil adsorbing capacity under the aqueous concentration of diuron at 1 mg/L.
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