【作者】 黄丽；

【导师】 刘凡；

【作者基本信息】 华中农业大学 ， 土壤学， 2004， 博士

【摘要】 土壤微域的化学特征、物质转化和环境状况，是土壤学研究中最活跃的领域之一。作为土壤形成过程中的产物和结构特征，处于土壤裂隙或孔隙壁表面的胶膜是土壤特定阶段和特定成分活动、迁移、沉积的化学微环境的记录、土壤中元素淋溶迁移的信息载体，又是土壤固相、液相、气相与植物根系相互接触、影响和作用的交汇场所。研究胶膜的物质组成与形态变化、营养和有毒污染元素的含量及生物有效性，对了解土壤性质和评价环境质量，以及认识土壤的发生与演变规律有重要的理论意义和实用价值。 本文用化学分析和X-射线衍射（XRD）、扫描电镜（SEM）、电子探针（EPMA）、偏光显微观察等技术，研究我国亚热带的黄褐土、黄棕壤和红壤铁锰胶膜及其基质的微形态特征、物质组成、表面化学性质以及元素迁移的地球化学特点。结果表明： 1．铁锰胶膜的微形态特征为黑色和红褐色相间、厚度约为1mm的膜状物，它的物质结构致密，与基质的界限较清晰。SEM／EPMA分析表明，MnO₂和Fe₂O₃在胶膜线剖面上呈波形曲线分布；黄褐土和黄棕壤的铁锰胶膜由外向内，出现富锰区、富铁锰区和富铁区，并在胶膜表面呈锰-铁锰-铁胶膜相间的条带状构造；红壤胶膜条带由外向内为富铁锰区和富铁区，富锰区不明显：三种土壤由南到北，土壤铁锰胶膜的富锰区逐渐明显。胶膜的生长起源于渍水的环境，它的发育是在氧化-还原周期性变化过程中进行的。供试黄褐土、黄棕壤和红壤的铁锰胶膜条带的形成经历了多次较大的环境变化。 2．供试红壤、黄棕壤和黄褐土铁锰胶膜的pH值、铁的活化度，以及粘粒、盐基、Fe₂O₃、P₂O₅、非晶形铁、游离铁、MnO₂、Co、Pb、Li、Cu、Zn、Ni、Cd等含量均比基质土壤明显的高。重金属元素尤其是Co、Pb等在胶膜中大量累积，说明这些元素在胶膜形成中发生了分异，并随铁、锰氧化物在胶膜上的淀积而富集。Ba、Co、Cu、Li、Ni、Pb等元素主要富集于铁锰胶膜的氧化锰矿物中，而Zn、Cd、Cr、Mo主要富集在氧化铁矿物中。 3．成土的气候环境和物质组成的差异，使三类土壤铁锰胶膜的形成各有特点。黄褐土的成土作用相对较弱，在胶膜的物质迁移过程中，MnO₂对Co、Pb、Cu、Cd、Ni等大部分重金属离子的富集起主导作用；随着成土作用的增强，黄棕壤中除MnO₂外，铁氧化物在胶膜形成过程中的作用加强，并且胶膜中对重金属元素地球化学行为影响的作用较集中；红壤胶膜湿润、酸性强，MnO₂在铁锰胶膜形成过程中富集重金属元素的作用下降，粘粒和铁氧化物的影响加强。即从黄褐土到黄棕壤，胶膜中影响重金属行为的作用逐渐聚集，在黄棕壤中表现得最集中，相互影响较强烈；在红壤胶膜中，这些成土作用又变得较分散，相互之间的影响减弱。 4．供试的铁锰胶膜与基质土壤的粘土矿物均由水云母、高岭石和1.4nm矿物组成。黄褐土和黄棕壤基质中的1.4nm矿物为1.4nm过渡矿物和蛭石的混合相，但胶膜中的1.4nm矿物全部为蛭石；红壤胶膜和基质中的1.4nm矿物均为1.4nm过渡矿物和蛭石的混合相。由此认为，黄褐土和黄棕壤胶膜中的蛭亚热带几种土壤铁锰胶膜的微形态特征、物质组成、性质及地球化学特点石主要来源于表层粘粒中蛙石的淀积和裂隙周围基质土壤中1.4nm过渡矿物的转化;在胶膜微环境条件下，其有机质含量、交换性盐基总量等性质明显不同于基质土壤，其微环境抑制了土壤中的蛙石向1.4nm过渡矿物转化，并导致1.4nm过渡矿物向蛙石的转化。 5.有机酸盐溶液对黄棕壤和黄褐土基质粘粒的矿物培养试验结果表明，经柠檬酸钠和乙酸钠溶液培养4至7个月后，基质土样中的部分1.4nln过渡矿物已逐渐向蛙石转化:与其它处理相比，用0.5m。比的柠檬酸钠和盐溶液培养基质土壤7个月后，其1.4lun过渡矿物向蛙石转化最为明显。说明土壤经有机酸盐溶液培养后，部分1.4 nm过渡矿物的层间轻基铝被络合出层间，随后钾、钙、镁等的水合阳离子进入，使之转化为蛙石;有机酸盐的种类、浓度和培养时间的长短均对转化的进程起重要作用。这证实了胶膜中有机质和盐基含量更高的微域条件，是导致1.4nm过渡矿物的演化逆转为蛙石的主要原因。 6.供试铁锰胶膜和基质土壤的氧化铁矿物主要为针铁矿，大部分胶膜中针铁矿的铝同晶替代量小于相应的基质土壤，这主要是胶膜的复盐基以及有机质对铝的鳌合作用使铝的活性受到抑制所致。黄褐土和红壤铁锰胶膜的锰矿物为铿硬锰矿和水钠锰矿的组合，黄棕壤铁锰胶膜的主要为水钠锰矿。 7.与基质土壤比较，铁锰胶膜的比表面积大，PZC低。铁锰胶膜经脱锰处理后，比表面积明显降低。由STPT法测得黄褐土、黄棕壤、红壤基质的PZC分别为3.13、3.65、3.90;黄棕壤和红壤铁锰胶膜的PZC分别为3.26和3.42，黄褐土的铁锰胶膜测不出PZCo 8.铁锰胶膜对Pb2+、cu2+、c子+、zn2+的吸附曲线符合l朋gmuir方程。与基质土壤相比，铁锰胶膜对重金属离子的吸附和氧化能力强。铁锰胶膜经脱锰处理后，对P价+、cu2+、cd2+、zn2+的最大吸附量比未处理的降低了53%一100%;其氧化cr（In）生成cr拟)的量比铁锰胶膜的降低了87%一100%。说明红壤、黄棕壤、黄褐土的铁锰胶膜中，氧化锰是吸附重金属离子和更多还原

【Abstract】 The micromorphology, compositions, surface chemical properties and element geochemical characteristics of iron-manganese cutans and matrix soils in yellow cinnamon soil, yellow brown earth and red soil were studied by chemical analyses, XRD, SEM and EPMA techniques in subtropical zone in China. Results showed:1. The micromorphological structure of iron-manganese cutan was a thin black film alternating with red and brown, and about 1 mm thick covering on soil particle.The structures of cutan materials were denser, and the boundarys between cutans and matrix soils were clearly. SEM/EPMA analyses showed that the line distributions of MnO2 and Fe2O3 contents in iron-manganese cutan profile were wave-like curves. There were manganese-rich region, iron-manganese-rich region and iron-rich region from outside to inside of iron-manganese cutans in yellow cinnamon soil and yellow brown earth, and they presented alternate belt structures of manganese cutan, iron-manganese cutan and iron cutan. But from outside to inside in the belt tructure of iron-manganese cutans in red soil, there were only iron-manganese-rich region and manganese-rich region.The manganese-rich regions in belt tructures were gradually obvious from south to north. The growth of cutans came from flooding-water environment, and they gradually grew in the oxidation-reduction process. The formation of belt tructure in iron-manganese cutans would probably undergo several great landscape and soil environment changes in yellow cinnamon soil, yellow brown earth and red soil.2. The pH, Feo/Fed, contents of clay, base ions, MnO2, Feo, Fed, Fe2O3, P2O5, Co, Pb, Li, Cu, Zn, Ni, Cd etc. in iron-manganese cutans were notable higher than those in corresponding matrix soils. Heavy metals enriched in iron-manganese cutans especially Co and Pb, this showed that these elements separated from matrix soils and enriched in cutans going with illuvial iron oxides and manganese oxides during the formation of cutans. In cutans, Ba, Co, Cu, Li, Ni, Pb mainly enriched in manganses minerals, and Zn, Cd, Cr and Mo mainly existed in iron minerals.3. The formations of three iron-manganese cutans were different because the difference of their material compositions, soil-forming climate and environment. The soil-forming processes were weak in yellow cinnamon soil, the element transformations of cutans mainly effected by MnO2 which enriched heavy metal elements of Co Pb Cu Cd Ni etc. In yellow brown earth, the effects of iron oxides inceased in addition to MnO2 in cutan formation, and the actions that influenced geochemical acts of heavy elements in cutans was close.The cutans in red soils were wet and acide.The acts that MnO2 enriched heavy elements decreased in the course of cutan formation in red soil, and effects of clay and iron oxide increased. From yellow cinnamon soil to yellow brown earth, the effects of influencing heavy element acts gradually get togather. These factors concentrated andinteracted more violently in iron-manganese cutans of yellow brown earth. But in cutans of red soil, these factors became more dispersed and little interacted.4. The cutans and matrix soils all contained hydromica, kaolinite and 1.4 nm mineral in tested samples. Both vermiculites and 1.4 nm intergrade minerals were present in matrix soils, whereas only vermiculites were detected in iron-manganese cutans in yellow cinnamon soil and yellow brown earth. The 1.4 nm minerals were all consisted of1.4 nm intergrade minerals(HIV) and vermiculites in cutans and matrixes in red soils. fThis suggested that the vermiculites in cutans mainly came from the vermiculites in clays illuviating from the topsoil or changes of 1.4 nm intergrade minerals in clays moving from the matrix soils around cracks in yellow cinnamon soil and yellow brown earth. The contents of organic matter, exchanged bases and pH value were different between cutans and matrix soils, so the factors in the microregions restrained the transforms of vermiculites to 1.4 nm intergrade minerals or led to the chan更多还原