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  • 學位論文

添加二氧化錳與葡萄醣對蛇紋岩土壤中三價鉻氧化能力之探討

Effects of manganese oxide and glucose on chromium(III) oxidation potential in serpentinitic soils.

指導教授 : 許正一

摘要


蛇紋岩是超基性火成岩經變質作用所產生,主要礦物為蛇紋石,經風化後的蛇紋岩土壤含有高濃度的鉻、錳、鎳、鈷,尤其是鉻、鎳濃度往往會遠超過環保署所公告之土壤污染管制標準。鉻是存在於自然界中具氧化還原活性的一種重金屬,主要氧化態為Cr(Ⅲ)及Cr(VI),當土壤中存在Mn(III, IV)氧化物時則可將Cr(III)氧化成Cr(VI)。本論文採取台灣東部35個蛇紋岩土壤樣品,進行Cr(VI)濃度與蛇紋岩土壤性質之間的相關性比較,並選取部分樣品添加二氧化錳及葡萄醣,觀察二氧化錳是否會將蛇紋岩土壤中的Cr(Ⅲ)氧化為毒性較強的Cr(VI),接著以滅菌處理來觀察微生物對鉻氧化還原變化的影響。研究結果顯示,蛇紋岩土壤中雖富含鉻及錳,但是六價鉻濃度與所有可萃取性錳之間呈負相關,游離性鉻(Crd)則是與水溶性錳(Mnw)、還原性錳(Mnh)呈正相關(r=0.618*、0.673*)。當蛇紋岩土壤中添加MnO2時,的確能使Cr(VI)濃度增加,且部分樣品Cr(VI)溶出量已超過台灣的地下水污染管制標準。進行添加葡萄醣處理後,能夠抑制Cr(VI)產生,其氧化能力會受到生物性或非生物性抑制的效果。滅菌處理後添加MnO2及葡萄醣的研究中也可觀察到,經由滅菌處理比未滅菌處理時,所測得之Cr(VI)濃度較低,雖然去除了生物性作用機制後,卻可能因為滅菌過程中所釋放出的有機質而導致產生更強的還原作用。

並列摘要


Serpentinites are hydrothermally altered from igneous ultramafics, which dominant minerals are serpentines. Serpentinitic soils are characterized with large amounts of heavy metals like Cr, Mn, Ni, and Co which levels are generally over the Soil Pollution Control Standards of Taiwan. Chromium(Cr) is a naturally occurring and redox sensetive transition metal that has two main oxidation states, Cr(III) and Cr(VI), or simultaneously undergo oxidation-reduction interconversions in soils. Mn (III, IV) oxides are potentially able to oxidize Cr (III) into Cr (VI) in the environment. This study used a total of 35 soil samples from eastern Taiwan to correlate between Cr(VI) and soil properties. Moreover, spiking MnO2 and glucose to observe their influences on oxidation or reduction of Cr in association with effects of soil microbial activity. Experimental results indicated that there is no correlation between the concentration of Cr(VI) and all extractable manganese. The correlation of dithionite-citrate-bicarbonate extractable (Crd) with water soluble Mn (Mnw) and reducible Mn (Mnh) is 0.618、0.673(P < 0.05) respectively. Adding MnO2 in the soils are capable of oxidizing Cr(III) to Cr(VI), and the generated Cr(VI) in part of the samples was over the Groundwater Pollution Control Standard of Taiwan. However, our data suggested that glucose increased the rate of Cr(VI) reduction by both abiotic and biotic mechanisms. The factor screened included soil sterilization, through sterilization treatment was measured a lower concentration of Cr(VI) which labile organic matter was released through the sterilization and resulted in a stronger reduction process in the soils.

參考文獻


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