| Clay minerals are widely distributed in the surface of the earth,with characteristics of small size,large specific surface area,high activity,that significantly affect the soil physical,biological and chemical processes,the structure and types of clay minerals may indicate the evolution of the soil and the changes of environment.Studying zonal characteristics of clay mineral in the particles is important significance to revealing the clay mineral evolution law of soil and the soil formation.Several zonal soils(Brown soil,Yellow brown soil,Red soil and Lateritic)of granite and gneiss were collected from north to south of China in this paper,after isolating 450-2000 and 100-450 nm particles,inorganic nanoparticles(25-100 nm)were collected by an antomated ultrafiltration device(AUD),using synchrotron radiation X-ray diffraction(XRD),and other methods to analyze the different size particles,studying the differences and similarities of morphology and mineral structure in different size particles;clarifying the type of clay minerals,combination and evolution characteristics in soil particles;revealing zonal characteristics of clay mineral evolution from the level of nanoscale;enriching the study of the theory of the soil nano chemical and mineral.The main conclusions were:(1)From north to south,the phenomenon of desilication and aluminium rich existed in the soils of developing from granite and gneiss,the 2:1 type clay minerals reduced gradually and 1:1 type clay minerals and iron oxide content increased gradually,and a few gibbsite appeared.The clay minerals of Brown soils and Yellow brown soils were vermiculite,hydroxy interlayer mineral(HIV),illite-vermiculite mixed mineral(I-V),illite,kaolinite,kaolinite interstratified minerals(KIMs)and smectite.The main clay mineral of Red soils was kaolinite,following by illite,HIV(and a few vermiculite),illite-HIV mixed minerals(I-HIV),gibbsite.The clay minerals of Laterite were kaolinite,illite and gibbsite.The all tested soils existed goethite and hematite,Brown soils were dominate by hematite and others were goethite.(2)With decreasing of particle size,the edge of Brown soil and Laterite particles got roughly with decreasing of layer stacking.The 450-2000 nm Brown soil particles were flake and a small amount of thin strips.The Brown soil nanoparticles were flake of irregular,dense cluster and edge blur.The 450-2000 nm Laterite particles were dispersive arrangement of polygon flake and rods,the line numbers of polygon flake were between 4 to 6.The Laterite nanoparticles were rod,oval and polygon flake.The thickness of 450-2000 nm Laterite particles were 100 or 200 nm,and nanoparticles were about 6 nm.Compared with 450-2000 nm particles,the morphology of Laterite nanoparticles was more homogeneous and regular particles.(3)With decreasing particle size,the phenomenon of desilication and enrichment of iron and aluminum appeared,and silicon aluminum rate was a trend of decrease.Additionally,from north to south,the silica-alumina ratio was a trend of decreasing and crystalline iron was a trend of increasing.With particle size decreasing,the clay minerals transformed from 2:1 type to 1:1 type,trioctahedron to dioctahedron at the same time.From north to south,the main clay minerals were dioctahedron in nanoparticles,and changed from 2:1 to 1:1 type.Compared with 450-2000 and 100-450 nm particles,nanoparticles undergone stronger weathering,the main clay minerals were kaolinite,KIMs and illite.The content of kaolinite(and KIMs)and illite were 45% and 55% in Brown soils,respectively.The kaolinite content of Yellow brown soils,Red soils and Laterites were followed by 94,85 and 86%,illite content were between 3% to 9%.Additionally,a few vermiculite(4%)and HIV(5%)existed in Yellow brown soil and Red soil nanoparticles,a few gibbsite(5%)existed in Red soil and Laterite nanoparticles.The HIV of Red soils mainly had particles of 450-2000 and 100-450 nm in surface soils,the interlayer materials were hydroxy Al.(4)With particle size decreasing,the crystallinity of illite and kaolinite tended to decreasing.From north to south,illite crystallinity of nanoparticles decreased,and kaolinite crystallinity increased.Weaver index of illite was lowest in nanoparticles,but Kübler index and integral width(IB)was highest in nanoparticles.Illite chemical index(ICI)of most illite were lower than 0.4,mainly composed of physical weathering.d001 and d002 FWHM of kaolinite were highest in nanoparticles,the average diameter crystal(MCD),average layers(ALN)and H&B index were minimum in nanoparticles.With particle size decreased to nanoscale,Kaolinite dehydroxylation temperature decreased 7 to 17 oC.The decreasing of kaolinite crystallinity in nanoparticles was due to its surface hydroxyl and octahedral AlO6 layer decreased and iron in internal structure.(5)The illite of Brown soil and Laterite was high dense of defect,the illite transforming process of Brown soil and Laterite was layer-by-layer replacement of solid-state transformation.Illite defect of Brown soil 450-2000 and 25-100 nm particles were edge dislocation and screw dislocation of lattice fringes.Illite defect of Laterite 450-2000 nm particles were edge dislocation of lattice fringes and 25-100 nm particles were screw dislocation.Illite and vermiculite,illite and kaolinite mixed arrangement of lattice fringes were showed in Brown soil 450-2000 nm particles,illite and kaolinite mixed arrangement of lattice fringes in 25-100 nm particles.(6)The phyllosilicate minerals of nanoparticles mainly inherited from secondary minerals in larger particles(450-2000 and 100-450 nm).The evolution process of clay minerals in different size particles followed the way that the larger phyllosilicate minerals broken into small particle size of minerals at first,then 2:1 type transformed to 1:1 type.From north to south,the clay mineral evolution sequence of nanoparticles was: illite ? vermiculite ? HIV ? kaolintie(KIMs)? gibbsite.Compared with 450-2000 and 100-450 nm particles,some swelling minerals in nanoparticles disappeared,such as smectite,illite-HIV mixed mineral(I-HIV). |
PDF Full Text Request