日本關西及台灣東部地區蛇紋岩土壤性質之比較

comparison in the differences of serpentine soil properties between Japanese Kansai and eastern Taiwan

包國輝(Guo-Hui Bao)

指導教授 ： 許正一

國立屏東科技大學/工學院/環境工程與科學系所/碩士(2010年)

https://doi.org/10.6346/NPUST.2010.00069

摘要

蛇紋岩為橄欖石等超基性岩類經變質作用而成，多分佈於板塊交界處。由蛇紋岩類所風化而成的蛇紋石土壤(serpentine soils)Ca/Mg比值偏低，且含有大量鉻、鎳、鈷等重金屬，最高濃度可遠超過台灣的土壤污染管制標準。此類因地質因素所造成重金屬含量偏高之土壤，雖非人為污染所致，但一樣會影響生態環境與人體健康。另外，氣候條件與土地利用方式的差異，是影響重金屬在蛇紋石土壤中宿命的主要因素，因此本研究採取日本關西地區與台灣東部之蛇紋岩土壤共8個剖面，依化育層分析必要的理化性質，且以有效性單一試劑抽出法(single extraction)與序列萃取法(sequential extraction)測定不同型態的鉻、鎳、鈷，再以X-ray繞射及掃描式電子顯微鏡搭配能量散佈光譜儀探討這些重金屬的礦物起源，以了解溫帶與亞熱帶環境下母質風化對重金屬溶解移動的影響。研究結果指出，日本樣體因Ca/Mg比值較台灣樣體低，受風化程度較低，而所有樣體中鉻、鎳及鈷全量明顯高於非蛇紋石土壤，並且部分樣體已超過台灣的土壤污染管制標準。在型態劃分中，鉻、鎳、鈷主要被固定在礦物晶格內，故集中在殘餘態，而元素間移動性大小順序為鈷>鎳>鉻。至於重金屬的DTPA抽出方面，以鎳的含量為最高而鉻最低，與序列萃取之型態分佈趨勢差異相符，表示蛇紋岩土壤中的鉻應最不易被植物所攝取。如以台灣的有機農業土壤重金屬容許量所使用的0.1 N HCl抽出來評估，則兩個水稻田表土層中的鉻及鎳皆超出此一容許量。此外，在礦物鑑定中，能夠發現蛇紋石及常與蛇紋石化作用伴隨的礦物蹤跡。在蛇紋岩土壤中，具有鐵磁性的鎳及鈷含量越高，其飽和磁化強度也有增加的趨勢。

關鍵字

蛇紋岩土壤 ； 重金屬 ； 單一試劑抽出法 ； 序列萃取 ； 超導量子干涉儀

並列摘要

Serpentinites, generally found in the margin areas between tectonicplates, are derived from ultramafics like peridotites. Serpentine soils from serpentinites are characterized by low Ca/Mg ratios and large amounts of heavy metals like Cr, Ni, and Co which can be over the soil pollution control standards (SPCS) of Taiwan. These heavy metals are not produced from human activities in serpentine soils, but may have adverse effects on eco-environment and human health. In addition, climate and land uses are major factors in controlling the fate of heavy metals in the soils. This study used eight pedons from Kansai of Japan and eastern Taiwan to analyze the soil horizon properties, determine the concentations of Cr, Ni, and Co by single and sequential extractions, and explore the metal origin in the minerals by XRD and SEM/EDS. The aim is to understand the influence of parent material weathering on the soils from temperate and subtropical regions. Experimental results indicates that the Japanese pedons were low weathered compared to Taiwanese due to the low Ca/Mg ratios in the Japanese soil samples. However, total contents of Cr, Ni, and Co in all soils were much higher than other non-serpentine soils, and the metal levels in some of them were over the SPCS of Taiwan. Regarding the metal fractionation, Cr, Ni, and Co were mainly from the mineral lattices, and thus were concentrated in the residual fractions. The mobility sequence followed as Co > Ni > Cr. With respect to DTPA extractable amount, Ni was the highest and Cr was the lowest. The difference in the DTPA extraction between metals was corresponding to the results of lability evalauted by sequential extraction; however, Cr is hardly absorbed by plant. Chromium and Ni concentrations in the surface soils of two paddy pedons were over the soil quality standard in Taiwanese organic famring which was evaluated by 0.1 N HCl. Moreover, serpentine mineral groups and accessory minerals have been identified in the soils. Nickel and Co contents in the soils increased with the increase of saturated magnetic susceptibility.

並列關鍵字

serpentine soil ； Heavy metals ； single extraction ； sequential extraction ； SQUID

參考文獻

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