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Red soil chemistry and mineralogy reflect uniform weathering environments in fluvial sediments, Taiwan |
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| Authors: | Tsung Ming Tsao Yue Ming Chen Hwo Shuenn Sheu Shung Yao Zhuang Ping Hua Shao Hua Wen Chen Kai Shuan Shea Ming Kuang Wang Yen Horng Shau Kai Yin Chiang |
| Institution: | 1. The Experimental Forest, National Taiwan University, No. 12, Section 1, Chienshan Road, Chushan, Nantou, 55750, Taiwan 2. Biodiversity Research Center, Academia Sinica, 128, Academia Road, Section 2, Nankang, Taipei, 11529, Taiwan 3. Natural Synchrotron Radiation Research Center, 101 Hsinann Road, Hsinchu Science Park, Hsinchu, 30076, Taiwan 4. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, People??s Republic of China 5. Central Geological Survey, Ministry of Economic Affairs, Taiwan, No. 2, Lane 109, Huaxin Street, Zhonghe, New Taipei City, 235, Taiwan 6. Department of Agricultural Chemistry, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei, 10617, Taiwan 7. Department of Marine Resource, National Sun Yat-Sen University, No. 70, Lienhai Road, Kaohsiung, 425, Taiwan |
| Abstract: | PurposeInformation on the physicochemical properties, mineral species and micromorphology of lateritic soils and gravel soil layers in paleo-environmental soil profile is severely lacking. Red soil profile of the Taoyuan terrace was employed to demonstrate its different extents of lateritic weathering. The objectives of this study were to compare the physicochemical properties of lateritic soils and gravel soil layers and identify using conventional and synchrotron X-ray diffraction (XRD) analyses mineral species in nanoparticles separated by automated ultrafiltration device (AUD) apparatus.Materials and methodsSoil samples were collected from paleo-environmental lateritic soils. Soil samples were examined using elemental analysis, conventional and synchrotron XRD analyses, high gradient magnetic separation, separation and collection of nanoparticles by AUD apparatus, and transmission electron microscopy (TEM).Results and discussionThe soil pH, redness index, quantities of free Al- and Fe-oxides (Ald and Fed), and clay content of lateritic soils are higher than those of gravel soil layers. Illite, kaolinite, gibbsite, quartz, goethite, and hematite were identified in clay fractions and nanoparticles by conventional and synchrotron XRD analyses. TEM images show presence of hematite nanoparticles on the surface coating of kaolinite nanoparticles and aggregated hematite nanoparticles overlapping the edge of a kaolinite flake in a size range of 4?C7?nm. Synchrotron XRD techniques are more straightforward and powerful than conventional XRD with random powder methods for identifying nanoparticles in red soils, particularly for illite, kaolinite, goethite, and hematite nanoparticles. According to chemical compositions of clay fractions and red soil features in the Taoyuan terrace, these red soils can be taken as lateritic red earths or red earths.ConclusionsThis work suggests that physicochemical properties, mineral species, and micromorphology of red soil at all depths can shed light on the extent of paleo-environmental lateritic weathering. |
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