Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/28096
標題: 重金屬污染土壤之不同單一與連續性抽出方法評估
Evaluation of Different Single and Sequential Extraction Procedures of Soils Contaminated by Heavy Metals
作者: 鄭光喆
Zheng, Kuang-Zhe
關鍵字: heavy metal;重金屬;single extraction;soil;sequential extraction;aqua regia digestion;連續性抽出;土壤;單一性抽出;王水消化
出版社: 土壤環境科學系所
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摘要: 
With industrial development and technical advance, some of the heavy metals used in artificial activities enter soil and cause contamination by improper handling. The most common method to determinate heavy metals in polluted soils is chemical extraction with different reagents. Chemical extractions includes single extractions and sequential extractions. Single extraction procedures extract heavy metals in soil by only one step, are usually time-saving, with easier process, and they can choose reagents for different purposes. Single extraction is suitable for differentiate mobility and bio-availability of heavy metals. Sequential extraction procedures extract different forms of heavy metals step by step, but they are time-consuming and with complicate process. However, sequential extraction procedures provide complete informations of different heavy metals forms in soil. It is possible to evaluate short-term and long-term impact of heavy metals against environment by sequential extraction results.
Recently, Taiwan conforms aqua regia digestion to regulate the control standard of heavy metal content in soil. However, this method cannot directly reflect the threat to environment by heavy metals. There are two objectives for this study. One is to compare the results of BCR and Tessier sequential extraction applying on six contaminated soils with different heavy metals content to understand the fractionations of the heavy metals. The other purpose is to apply seven single extraction procedures including H2O, 0.1M CaCl2, 0.11M HOAc, 0.005M DTPA, 0.05M EDTA, 0.1M HCl, 0.12M HNO3 and XRF detection on 30 samples with different heavy metals content, to compare the results from single extractions and aqua regia digestion and to evaluate the practicability of single extractions replacing aqua regia digestion by double sampling design.
Results of sequential extractions show that most of cadmium exists in exchangeable form than other heavy metals. In soils with low heavy metal concentration, most of copper and zinc are residual or reducible. In soils with high heavy metal concentration,most of copper and zinc would distribute in exchangeable form. Most of nickel and lead distribute in reducible or oxidisable form. Aqua regia digestion would overestimate the impact. chromium only distribute in reducible, oxidisable, and residual form. Few of chromium exist in exchangeable form, and it is harmless to the environment. Two sequential extractions lead to different results because of variation in methods. BCR procedure is an ideal method in terms of operation. Amont of heavy metals extracted by different single extraction reagent is in the following order: 0.1M HCl≥ 0.12M HNO3>0.05M EDTA>0.005M DTPA>0.11M HOAc>0.1M CaCl2>>H2O. 0.1M HCl extraction shows significant regression relationship between aqua regia digestion of Cd and Pb in these 30 samples. While results of 0.05M EDTA extraction show good regression relationship between aqua regia digestion of Cd, Cu and Pb. XRF detection shows the best regression relationship between aqua regia digestion in Cr, Ni, and Zn. It also shows significant regression relationship with aqua regia digestion of Cu and Pb. Applying double sampling to single extractions and aqua regia digestion shows 0.1M HCl can replace aqua regia digestion in Cd and Pb contaminated soils, XRF detection can replace aqua regia digestion in Cr, Cu, Ni or Zn contaminated soils. Analytical outlay can be saved and sample amount can be increased by applying two methods on specific polluted samples.

隨著工業發展與科技進步,在各種人類活動中被大量利用的重金屬,部分因為不當處理進入土壤而造成污染,以化學試劑抽出來測定污染土壤中之重金屬含量為目前最為廣泛使用的方法。化學試劑抽出可分為單一性抽出與連續性抽出,單一性抽出在單一抽出步驟中對土壤中重金屬抽出,步驟簡單,需時較短,並可依照各種不同目的以選擇試劑,適合區分界定環境中重金屬的移動性及生物有效性;連續性抽出乃以一連串的試劑逐步對於不同形態重金屬抽出,步驟較繁雜,所需時間長,但是對於土壤中重金屬的各種存在型態可得到較完整的資訊,並可由所得結果進一步評估重金屬對於環境短期與長期所可能造成的影響。
目前台灣對於土壤重金屬含量管制標準是以王水消化法所得重金屬總量為依據,然而此方法並不能直接反映出重金屬對環境之危害。本研究目的有二,第一是比較BCR與Tessier兩種連續性抽出法應用在六種受不同含量重金屬污染之土壤,了解重金屬存在之型態分布,並希望選擇出兩方法中較佳者。第二個目的則利用重金屬含量不同之30個樣品,使用七種單一性抽出(0.1M鹽酸、0.12M硝酸、0.11M醋酸、0.05M EDTA、0.005M DTPA、0.1M氯化鈣、水)以及X光螢光分析儀(XRF)與王水消化總量做比較,視彼此間相關性,以雙重採樣設計評估單一性抽出配合王水消化法使用,降低實際應用之花費的可行性。
連續性抽出結果顯示,鎘存在交換態的比例相對其他重金屬較高。銅與鋅在低濃度時主要分布在殘留態與可還原態,然而隨著總濃度提高,會轉變為以交換態分布為最多。鎳與鉛在土壤中有大部分是存在於可還原態或有機結合態,用王水消化法會高估危害性。而鉻只分布於可還原態、可氧化態及殘留態,幾乎沒有鉻以交換態的形式存在,相對來說在環境中較無害。兩種連續性抽出法由於方法不同導致結果差異,而BCR法以實驗操作的觀點來說較理想。單一性抽出試劑的抽出能力:0.1M 鹽酸 ≧ 0.12M 硝酸 > 0.05M EDTA>0.005M DTPA > 0.11M 醋酸 > 0.1M氯化鈣 >>水。0.1M鹽酸對於鎘與鉛的抽出,在30樣品的結果與王水消化之總量有極顯著的迴歸,0.05M EDTA在鎘、銅、鉛與總量間迴歸極顯著,而XRF除了在鉻、鎳及鋅的結果與總量間迴歸為各種方法中最佳之外,在銅與鉛也有顯著迴歸。雙重採樣設計以單一性抽出配合王水消化法之結果中,鎘與鉛適合以鹽酸抽出,鎳、銅、鉻及鋅可以XRF分析,對於不同重金屬分別利用不同分析方法可增加分析之樣品數而節省實驗費用。
URI: http://hdl.handle.net/11455/28096
其他識別: U0005-2708200710093800
Appears in Collections:土壤環境科學系

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