稻田土壤中黑炭與其他成分對達有龍農藥吸附行為之研究

The sorption behavior of Diuron on black carbon and other constituents in the soils of rice field

邱建韶(Jiann-shaur Chiu)

指導教授 ： 吳先琪

國立臺灣大學/工學院/環境工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.01723

摘要

在台灣南部地區農民常在秋天稻草收割後，就地露天燃燒，此種燃燒行為會產生大量的黑炭，累積於土壤中。本實驗的目的在於估計台灣中南部地區農田的黑炭量，以及評估農田黑炭的含量對於除草劑之有效性與宿命是否會造成影響。
本論文測定土壤黑炭含量的方法，係先以酸去除土壤中的碳酸鹽，在充足的空氣中加熱375℃，再使用元素分析剩餘物質的碳元素；較佳的取出黑炭的方法，係使用化學分離再以比重分離，從土壤中取出密度為1.8至2.05 g/cm3的黑炭。研究中並使用吾人在農田裡自行燃燒稻草所產生的黑炭做比較；以達有龍水溶液作為吸附質，以批次的方法進行黑炭與土壤的等溫吸附實驗，並使用固相微萃取技術(SPME)配合氣相層析儀和電子捕捉偵測器作為量測水溶液濃度的工具。土壤的吸附量以dual-mode模式，並分別計算出黑炭及其他成分的吸附量對於土壤整體的吸附量所佔的比例，以評估黑炭的影響性。
從彰化線西土中，使用比重法分離出的黑炭比表面積為14 m2/g，碳元素含量為17%，自行燃燒稻草所產生的黑炭，其比表面積為78 m2/g，碳元素含量為14%，其比表面積差異的原因在於黑炭是否有經過長期在環境中馴化(aging)。
在彰化線西的土壤實驗裡，假設土壤吸附量為有機質和黑炭吸附所貢獻，使用dual-mode模式，扣除模擬比重分離的黑炭之吸附量，算出的達有龍對土壤有機質平衡係數(logKOC)為2.85 L/kg。由模擬結果顯示，黑炭吸附所佔的比例在吸附質濃度低時較大，且使用一地區所分離的黑炭，不適合模擬其他地區的土壤與黑炭吸附行為，黑炭之吸附量在達有龍濃度為1 mg/L時係佔土壤吸附量的64%。若達有龍被吸附後將會失去有效性，則黑炭含量對於除草劑的有效性及最適用量是有影響性的。

關鍵字

黑炭 ； 達有龍 ； 固相微萃取 ； dual-mode 模式 ； 土壤 ； 除草劑

並列摘要

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.

並列關鍵字

black carbon ； diuron ； solid-phase microextraction(SPME) ； dual-mode model ； soil ； pesticide

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