干旱半干旱地区土壤矿物组成特征及其环境意义

对处于干旱、半干旱地区的甘肃省15个地点的灰钙土、栗钙土、黑垆土、灰褐土和黄绵土等不同类型土壤剖面进行了机械组成分析、矿物组成显微鉴定和粘土矿物X射线衍射分析.结果表明:土壤机械组成以粉砂为主,粘粒次之;栗钙土、灰钙土、黑钙土和灰褐土等于旱地区典型土壤中表层的粘粒质量分数相对较低,土壤原生矿物组成以石英为主,绿帘石等蚀变矿物质量分数较高,次生矿物含有较高的石膏和方解石等;粘土矿物主要为伊利石、绿泥石、高岭石和蒙脱石.土壤机械组成、矿物组成和粘土矿物组成表明:干旱、半干旱地区土壤为黄土母质,土壤形成条件为碱性环境、较弱的淋滤作用和干冷气候,近代强烈的风蚀作用(或沙尘暴)和大气污染对土壤有一定程度的改造.

Mineral compositions of soil in the arid and semiarid region and their environmental significance

The sierozem, chestnut soil, chernozem and yellow cotton soil and other different types of soil profiles from 15 selected sites in Gansu, China have been investigated into and sampled in order io gain insight into mineral compositions of soils in the arid and semiarid regions. Their grain compositions have also been studied in present paper and the mineral compositions of all the samples were identified and counted under a microscopy. Clay minerals were analyzed by X-ray power diffraction and the results show that the soil textures in the studied area are dominated by firstly silt and secondly clay, typical soils in arid, and semiarid region, such as sierozem, chestnut, and chernozem, contain lower contents of clay at topsoil. The soils are mainly composed of quartz in primary minerals, and of abundant epidote etc. in alteration minerals and gypsum and calcite etc. in secondary minerals, secondary hornblende, biotite, muscovite etc. Clay of soil is characterized by illite, chlorite, kandite and smectite. Collectively, the grain, mineral and clay compositions suggest that the parent materials of soils in the arid and semiarid region are loess and their formation condition of soils were cold weather, alkali condition, weak eluviation, and neoteric durative intensive aeolation (or dust storm) and air-pollution.