几种地带性土壤纳米颗粒的物质组成与粘土矿物演化特点

Soil nanoparticles are very active, and their clay minerals have important influences on the physical and chemical actions of soils. Study on the zonal character of the clay mineral compositions in soil nanoparticles is significance to reveal the evolution laws of clay minerals and the pedogenic processes of soils in our country. In this project, the objects are the main zonal soils (Latosols, Red soils, Yellow-brown soils and Brown soils) that developed in China from the south to the north. After the particles in the size of 450-2000 and 100-450 nm are separated by routine method, the two kinds of soil nanoparticles (the inorganic nanoparticles and the nanoparticles of inorganic and organic complex) in the size of 25-100 and 1-25 nm are separated by the Automatic Ultrafiltration Device (AUD). The constituents of particle fractions, elements and minerals are tested in the nanoparticles, and the change of material compositions and silica-alumina ratios in the nanoparticles are determined. The difference between the two kinds of nanoparticles in the respect of mineral structure, micromorphological feature, self-assembling action and surface chemical property are analyzed. The results could show the type, constituent and evolution of the clay minerals in the different sizes of nanoparticles, and their relationship with the zonal distribution of soils. And the effects of clay mineral compositions on the element distributions and surface chemical properties of the nanoparticles in the zonal soils are discussed. The study would clear the relationship between the clay mineral compositions in the nanoparticles and the changes of the mineral constituents in the zonal soils, and reveal the characteristics of clay mineral evolution in the zonal soils developed from the south to the north in China from a nano-scale to enrich the academic study of soil nano-chemistry and soil genetic classification.

土壤纳米颗粒性质极为活跃，其粘土矿物对土壤理化性质有重要影响。研究纳米颗粒中粘土矿物的地带性特点，对揭示我国土壤的粘土矿物演化规律及其成土过程有重要意义。本项目在分离出我国从南到北的主要地带性土壤（砖红壤、红壤、黄棕壤、棕壤）中450-2000、100-450 nm的颗粒后，再用纳米粒子超过滤器分离其中25-100和1-25 nm 的无机纳米颗粒和有机无机复合体纳米颗粒，测定其粒级、元素和矿物组成，明确地带性土壤纳米颗粒的物质组成与硅铝率等变化特点；研究其无机和有机无机纳米颗粒的矿物结构、微形貌、自组装行为和表面化学性质的异同；明确纳米颗粒中粘土矿物类型、组合和演化特点，及其地带性；探讨纳米矿物组分的变化对土壤元素分布和表面性质的影响；阐明纳米颗粒中粘土矿物的组成与地带性矿物组合变化的关系，从纳米尺度揭示我国南北土壤粘土矿物演化的地带性特点，以丰富土壤纳米化学和土壤发生分类的理论研究。

本研究以我国由北到南分布的主要地带性土壤（棕壤、黄棕壤、黄褐土、红壤和砖红壤）为对象，采用纳米粒子超过滤器（AUD）和同步辐射X射线衍射（XRD）等手段对土壤颗粒（<2000、450-2000、100-450和25-100 nm）进行分析，研究不同粒径颗粒的形貌和物质组成的异同；阐明土壤颗粒中粘粒矿物的类型、组合和结构特点；探讨由北到南的地带性土壤纳米颗粒（25-100 nm）中粘土矿物的结构转变与演化特征；从纳米尺度揭示我国水平地带性土壤中粘粒矿物演化的地带性规律。.研究表明，1）由北到南，供试土壤存在脱硅富铝化的现象，土壤中2:1型粘粒矿物的含量逐渐减少，而1:1型粘粒矿物和铁氧化物的含量逐渐增加，并出现三水铝石。2）随着颗粒粒径减小，粘粒矿物由2:1型向1:1型转变以及由三八面体向二八面体转变；由北到南，纳米颗粒中粘粒矿物均以二八面体矿物的演化为主，并由2:1型向1:1型转变，且晶形铁氧化物增加。相比450-2000和100-450 nm颗粒，纳米颗粒经受更为强烈的风化作用，其主要粘粒矿物均为高岭石（和高岭石-2:1间层矿物KIMs）和伊利石。3）土壤颗粒中粘粒矿物随着粒径变小其层状堆垛减少，颗粒的边缘变得模糊。相比450-2000 nm颗粒，砖红壤纳米颗粒高度约为6 nm，其大小更加均一，并具有较多规则形貌的颗粒。4）随着颗粒粒径减小，供试土壤颗粒存在脱硅、富集铁铝的现象，其硅铝率呈降低的趋势。由北到南，纳米颗粒中硅铝率降低。5）随着颗粒粒径减小，伊利石和高岭石的结晶度均存在降低的趋势。由北到南，纳米颗粒中伊利石的结晶度降低，而高岭石的结晶度增加。6）棕壤和砖红壤纳米颗粒中，弱结晶态的伊利石具有高密度的晶格缺陷，主要受晶格位错和混层矿物的影响。砖红壤纳米颗粒中伊利石的缺陷主要来自螺旋位错。棕壤和砖红壤颗粒中伊利石的转变过程为层-层替换的固相转变。7）供试土壤纳米颗粒中粘粒矿物主要继承大颗粒（450-2000和100-450 nm）中已有的次生矿物。由北到南，纳米颗粒中粘粒矿物演化序列为：伊利石→蛭石→HIV→高岭石（和KIMs）→三水铝石。