蛇紋岩土壤含有高濃度的鉻、鎳等重金屬,且往往會遠超過環保署所公告之土壤重金屬管制標準。由於蛇紋岩土壤中鉻與鎳來自不同礦物,其鎳的溶解度與移動性遠高於鉻,且目前蛇紋岩水稻田土壤的研究並不多,因此本論文以探討蛇紋岩水稻田土壤中鎳的可溶性為主。本研究採自台灣東部與日本關西地區之蛇紋岩水稻田二樣體土壤,進行理化性質分析,並以選擇性萃取的方式測定樣體中鐵、錳、鎳的含量。研究結果顯示,二處雖屬蛇紋岩土壤,但由於氣候條件、風化程度及土地利用不同,土壤性質也有所不同,二處樣體全量鎳的範圍,分別為240-316 mg/kg及326-520 mg/kg,遠高於台灣的土壤污染管制標準。若以0.1N HCl 抽出量來評估,皆超出有機農業土壤重金屬之容許量,且DTPA所抽出鎳的含量遠低於全量,所以鎳在土壤中易被礦物晶格所固定,並不易於植體所吸收。若將選擇性萃取濃度與土壤性質進行相關性分析,皆有良好之正負相關性,土壤中的鎳會與結晶型鐵氧化物結合,故鎳在土壤中的移動性,將會受到結晶型鐵氧化物的影響。 關鍵字:鎳、水田土壤、選擇性萃取、蛇紋岩
Serpentinite soil contains high concentration of heavy metals like chromium(Cr) and nickel(Ni) which may be above the soil pollution control standard of EPA(Environmental Protection Agency) in Taiwan. The solubility and mobility of nickel in soil is far higher than chromium due to their formation of different minerals. This study researched and discussed about the solubility of nickel from serpentinite soil in rice paddy field since relative issues were rarely studied in the past. Samples of serpentinite soil rice paddy fields from two regions, eastern Taiwan and Kansai(Japan), were collected and analyzed through both chemical and physical properties, and determined the content of Fe, Mn and Ni by selective extraction. The result shows the differences of soil properties are causing by the differences of climates, weathering and land use between two regions. The concentration ranges of nickel in samples are 240-316 mg/kg in eastern Taiwan and 326-520 mg/kg in Kansai which are much above the control standard in Taiwan. In 0.1N HCl extraction, both of these two regions are above the tolerance of heavy metals in soils of organic agriculture but the concentration of nickel by DTPA extraction is far less than the result of total extraction. The nickel is consisted in the crystal lattice and rarely absorbed by plant. In the analysis of correlation between selective extraction and soil properties, there are both good in positive or negative correlations. The nickel in serpentinite soil will embed with crystalline Fe oxide, and then results the affection of mobility in soil. Key words: Nickel, paddy soils, selective extraction, serpentinites