Goethite in an Alfisol and an Ultisol of Southern Taiwan
Other Title
臺灣南部一個淋溶土與一個極育土之針鐵礦
Journal
中華農學會報
Journal Issue
新182
Pages
83-98
Date Issued
1998-06
Author(s)
Jen-Chyi Liu
Zueng-sang Chen
G. Norman White
Joe B. Dixon
劉禎祺
陳尊賢
Abstract
One Alfisol and one Ultisol were selected from Kenting National Park in southern Taiwan to study their iron oxide minerals and A1 substitution for Fe in these oxides by the differential x-ray diffraction (DXRD). The differences of physical and chemical properties between these two soils are mostly in soli Ph AND BASE SATURATION PERCENTAGE. Both soils contain appreciable percentages of iron oxide (54 to 63g/kg Fed) that is predominantly goethite. Goethite was identified in the clay fraction of A and Bt horizons of both soils by the DXRD method. High crystalline index value (0.7 in Fed/Fet or 0.6-0.7 in (Fed-Fe0)/Fet) and very low iron activity ratio (0.04-0.15 in Fe0 /Fed) indicated little evidence for the presence of ferrihydrite in these soils formed in tropical environment. Calculation of A1 substitution for Fe was based on x-ray diffraction (XRD) measurement of d-spacings on the d111 and d111-110 which indicate about 10 to 15% in two studied soils. The A1 substitution for Fe is about the same amount in both soils yet there is evidence for slightly higher substitution in the goethite of the Alfisol than in the Ultisol. The results also suggested that there is evidence of a modest increase in A1 for Fe substitutin in the goethite of subsoils versus the top soils.
在臺灣南部墾丁國家公園各選擇一個淋溶土與一個極育土土壤樣體，藉由示差X- 射線繞射(Differential X-ray diffraction, DXRD)研究其鐵氧化礦物以及這些礦物中之鋁取代作 用。研究結果指出，兩不同土壤間理化性質之主要差異為土壤pH值及鹽基飽和度。兩研究 土壤均以針鐵礦為主要之鐵氧化礦物，其所含之游離氧化鐵(Fed)約在54到63g/kg之間， 而針鐵礦在本研究中係以示差X-射線繞射法在兩土壤之表層(A)及黏聚層(Bt)之黏粒中加以 鑑定。本研究區土壤之高結晶性指標值(Fed/Fe1比值為0.7或(Fed-Fe0)Fet比值為0.6-0.7) 以及非常低的鐵活性比值(Fe0/Fed比值為0.04-0.15)均顯示在此一熱帶環境下，均僅有少量 之水化氧化鐵(Ferrihydrite)生成。鐵氧化礦物中鋁取代量之計算係根據X-射線繞射在針鐵礦 111面(d111)之間距或以針鐵礦111面和110面間距之差值(d111-110)代入Schulze方程式中求得， 本研究中兩土壤之鋁取代量（莫耳百分比）平均約在10到15%之間。其中，淋溶土中針鐵 礦之鋁取代量略高於極育土中針鐵礦之鋁取代量；由結果亦顯示，兩土壤由表層至底層，針 鐵礦之鋁取代量均有適度增加的情形存在。
Subjects
Alfisol
ultisol
Differential x-ray diffraction
Goethite
Crystalline index of Fe
Iron activity ratio
Ferrihydrite
Al substitution
淋溶土
極育土
示差X-射線繞射
針鐵礦
鐵結晶性指標
鐵活性比
水化氧化鐵
鋁取代
Publisher
中華農學會
Type
journal article