海南岛北部玄武岩上土壤发生研究 Ⅱ.铁氧化物特征

GENESIS OF SOILS DERIVED FROM BASALTIN NORTHERN HAINAN ISLANDⅡ.IRON OXIDES

研究了海南岛北部玄武岩上发育的不同风化成土年代土壤系列的铁氧化物特征。研究表明,随风化成土时间增加,土壤发生过程中形成的游离铁（Fed）以及铁游离度（Fed/Fet）增大,铁活化度（Feo/Fed）降低。穆斯堡尔谱分析显示风化成土时间从9×104a、64×104a至 181× 104a,土壤黏粒中形成的赤铁矿含量占铁氧化物的比例从16％、25％增至 48％。风化成土时间越短,土壤中针铁矿结晶程度越差。X-射线衍射结果表明土壤细土和黏粒中赤铁矿含量与风化成土时间呈正比增加。同时,土壤有磁铁矿含量减少、磁赤铁矿增加的趋势。

Characteristics of iron oxides in soils with a chronosequence developed from basalt have been studied in Northern Hainan Island. The results show that pedogenic free iron oxides(DCB-Fe) and Fed/Fet(ratio of DCB-Fe to total Fe)increase and Feo/Fed(ratio of active Fe to DCB-Fe)decrease with increase in soil-forming age. The ratio of pedogenic hematite to iron oxides reaches from 16% , 25% to 48% in soil clays at soil-forming age of 9 × 104a,64 × 104a to 181 × 104a determined by Mossbauer Spectroscopy. Furthermore the younger the soil-forming age, the poorer the crystallinity of goethite in soils. Also,X-ray diffraction studies indicate that the hematite contents in fine-earth fraction and clay fraction rise with increase in soil-forming age and that magnetite descends while maghemite ascends in content.