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准噶尔和塔里木盆地盐渍化土壤黏土矿物组成特征及成因
何 帅,谭文峰,谢海霞
1.新疆农垦科学院 新疆石河子市;2.石河子大学农学院资源环境系 新疆石河子市;3.华中农业大学资源环境学院 武汉市
摘要:
新疆是中国盐渍化土壤主要分布区,本研究在新疆准噶尔盆地和塔里木盆地采集不同盐化程度土壤,利用X-射线衍射仪、透射电镜、X射线荧光光谱技术,研究两个盆地内盐渍化土壤中黏土矿物的分布特点。结果表明:受干旱气候的影响,两大盆地盐渍化土壤中黏土矿物主要包括伊利石、蒙脱石、绿泥石和高岭石,其中塔里木盆地盐渍化土壤中蒙脱石含量极少。土壤次生碳酸盐δ13C和δ18O及黏土矿物D和δ18O测定结果显示,塔里木盆地采样点土壤形成期气候相对准噶尔盆地更干旱,这种干旱气候导致伊利石中K+不易脱去,从而影响蒙脱石形成。在相对湿润的准噶尔盆地,采样点盐渍化土壤中蒙脱石含量较高,且蒙脱石含量随着伊利石含量减少而增加,两者之间达到极显著负相关关系(r=0.81,n=30,P<0.01),表明土壤中存在伊利石向蒙脱石的转化过程。准噶尔盆地盐渍化土壤具备伊利石向蒙脱石转化所需要的水分条件和化学组分:①相对湿润气候条件下伊利石发生脱K+;②盐渍化土壤pH>8.5,使长石中的Si4+溶解,参与矿物转化过程;③盐渍化土壤溶液中大量Ca2+、Na+和Mg2+ 可进入伊利石层间占据K+ 空位,形成蒙脱石。同时,研究结果还显示10 cm以下土层土壤盐分含量与伊利石含量存在极显著负相关关系(r=0.76,n=22,P<0.01),表明10 cm以下土体中,盐分的存在利于准噶尔盆地盐渍化土壤中伊利石向蒙脱石转换。因此,气候和盐分含量是新疆两大盆地盐渍化土壤中黏土矿物形成和转化的主要影响因素。
关键词:  黏土矿物  组成  成因  盐渍化土壤  准噶尔盆地  塔里木盆地
DOI:10.13758/j.cnki.tr.2019.03.021
分类号:S153.6
基金项目:国家自然科学基金项目(41361051)和兵团重大科技专项项目(2015AA001-2)资助。
Composition and Genesis of Clay Minerals in Salinized Soils in Junggar Basin and Tarim Basin of Xinjiang, China
HE Shuai1,2,3,2,4, XIE Haixia3, TAN Wenfeng4
1.Xinjiang Academy of Agricultural Reclamation Science;2.China;3.College of Agriculture,Shihezi Univerisity;4.Huazhong Agricultural University,Wuhan,Hubei ,China
Abstract:
Soil salinization is serious in the arid and semi-arid region in the northwest of China, especially in Xinjiang. In this paper, soil samples with different salt contents were collected in Junggar Basin and Tarim Basin of Xinjiang. X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray fluorescence (XRF) were employed to investigate the formation and distribution characteristics of clay minerals in salinized soil profiles. In these two basins, salinized soils with different salt contents had similar mineral composition including illite, montmorillonite, chlorite and kaolinite. In Tarim basin, illite is the main clay mineral while montmorillonite was bare. The analysis results of the δ13C and δ18O values in secondary carbonate and the D and δ18O values in clay minerals reflected that C4 plants were the dominant plant and the climate was relatively dry during the formation of salinized soils in Tarim Basin. The arid climate in Tarim Basin is unconducive for depriving K+ from illite, the content of montmorillonite reached the lowest point. The content of montmorillonite in salinized soils in Junggar Basin is significantly negatively correlated with the content of illite, (r=0.81, n=30, P<0.01). More specifically, this phenomenon demonstrates that illite in salinized soils was transformed to montmorillonite. In generally, this transformation is affected by water condition and requires the deprivation of K+ and Al3+, entry of Si4+, and replacement of K+ by Ca2+ and Na+ within lattice layers. According to the analysis, salinized soils in Junggar Basin have the required moist condition and chemical components to transform illite to montmorillonite: 1) Under the relative humid condition, K+ of illite in soil would be easily leached; 2) pH of salinized soil is high (pH>8.5), which promotes Si4+ of primary mineral to be readily dissolved. 3) Large amounts of Ca2+, Na+ and Mg2+ in soil solution of salinized soils. Thus, the content of montmorillonite in salinized soils in Junggar Basin is more than that in Tarim Basin. There is a significant negative correlation (r=0.76, n=22, P<0.01) between the contents of illite and salt in soil layers deeper than 10 cm, which indicates that soil layers below 10 cm depth are moister, the existed salts promote the transform of illite to montmorillonite in Junggar Basin. Thus, climate condition and salt content in salinized soils are the main factors for the formation and transformation of clay minerals in Junggar Basin and Tarim Basin of Xinjiang.
Key words:  Clay mineral  Composition  Genesis  Salinized soil  Junggar Basin  Tarim Basin

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