微地形下紫色土的矿物组成和pH的耦合特征

The Coupling Features of Mineral Composition and pH of Purple Soil Under Microtopography

为了研究微地形下紫色土的矿物组成和土壤酸度之间的关系,采集了重庆合川丘陵地区典型的紫色土壤,通过电渗析模拟酸化,并通过X射线衍射光谱分析电渗析前后的矿物组成以及酸度变化。结果表明:不同地形部位的紫色土随着地形部位的降低,土壤原生矿物的比重逐渐降低,土壤的发育程度越来越高。紫色母岩及其发育的土壤pH大小关系为母岩>石骨子土>半沙半泥土>豆瓣泥。pH变化与土壤中的方解石、钠长石和钾长石等矿物的含量有紧密关系。电渗析模拟土壤酸化后发现,石骨子土和半沙半泥土的pH分别降低了4.3,3.8个单位,同时土壤原生矿物分解风化,表明土壤原生矿物(如长石类矿物)可以缓冲土壤的酸化。

In order to study the relationship between the mineral composition and the acidity of the purple soil under the microtopography,the typical purple soil in the hilly area of Hechuan,Chongqing,was collected to simulate acidification by electrodialysis,and the mineral composition and acidity before and after the electrodialysis were analyzed by the X ray diffraction spectrum.The results showed that with the decreasing of topography,the proportion of the soil primary mineral decreased gradually,and the development degree of soil was higher and higher.The pH value of purple parent rock and its developed soils followed the order of parent rock〉stony sub-soil〉half sand half mud〉purple yellow mud.There had a clear correlation between the change of soil pH value and the contents of calcite,albite and potassium feldspar in soil.The pH values of stony sub-soil and half sand half mud decreased 4.3 and 3.8 units respectively after electrodialysis,while the primary minerals of soil decomposed and weathered,indicating that the soil primary minerals such as feldspar minerals could buffer the acidification of purple soil.