Inorganic Constituents in Soil (eBook)

Masami Nanzyo (Ph. D., Professor of Soil Science) Graduate School of Agricultural Science, Tohoku University. Awards: Japanese Society of Soil Physics Award (2005), Japanese Society of Soil Science and Plant Nutrition Award (2010), The Clay Science Society of Japan Award (2014). Hitoshi Kanno (PhD, Associate Professor)Graduate School of Agricultural Science, Tohoku University

Chapter 1 Purpose and scope This is an introductory chapter that includes 4 sections below.  Significance of visual aids in studying inorganic soil constituents is also described.  Principal purpose of this book is to provide basics and visual aids to beginners of soil science, environmental science and biogeochemistry.   1.1  Soil and ecosystem services 1.2  Functions of inorganic constituents in soil ecosystems 1.3  Analytical methods 1.4  Purpose and scope   Chapter 2 Primary minerals Major primary minerals in soils are introduced with optical and electron microscope images, energy dispersive X-ray analysis, and X-ray diffraction.  This chapter is one of the basic parts of the inorganic constituents in soil.  Exemplified minerals are separated from volcanic ash soils (new and old ones as much as possible) and a granitic soil.    2.1 Silica minerals and Silicate minerals 2.1.1 Grouping of silicate minerals 2.1.2 Quartz, Feldspar, Mica, Augite, Hypersthene, Hornblende 2.2 Ferromagnetic minerals   Chapter 3 Secondary minerals Major crystalline clay minerals including hydroxides and oxides in soils are introduced with optical and electron microscope images, energy dispersive X-ray analysis, and X-ray diffraction.  This chapter is also the basic part of the inorganic constituents of soils.  Minerals listed below were prepared from several different soils.  Although the examples are more or less a mixture with other minor ones, it is very difficult to separate a purely single clay mineral from soil.  Among these minerals, alteration of biotite is highlighted because partially weathered biotite is often found in soils and river deposits.   3.1 Grouping of secondary minerals 3.2 The 2:1 type minerals 3.2.1 Micacious minerals 3.2.2 Vermiculite 3.2.3 Smectite 3.2.4 Chlorite 3.3 The 1:1 type minerals 3.3.1 Kaolinite 3.3.2 Halloysite 3.4 Hydroxides and oxides 3.4.1 Gibbsite 3.4.2 Manganese oxides             Chapter 4 Non-crystalline inorganic constituents Volcanic glasses, plant opals, pedogenic opals, and short-range order minerals (allophane, imogolite) in Andisols are introduced with optical and electron microscope images, energy dispersive X-ray analysis. Among these, plant opals can be found in many soils under vegetation not only in the volcanic ash soils.  A thin section is used to show microscopic distribution of minerals in an Andisol.  Elemental composition of the short range order minerals such as allophane and imogolite is highly rich in Al while the parent materials of these short-range order minerals, volcanic ash is silica-rich.  Changes in element concentration during the process of short-range order minerals formation are discussed.   4.1 Poorly crystalline minerals in Andosols 4.1.1 Volcanic glasses 4.1.2 Plant opals 4.1.3 Pedogenic opal 4.1.4 Allophane and imogolite 4.2 Changes in element concentration during short-range order minerals      Chapter 5 Inorganic constituents sensitive to varying redox conditions   Minerals sensitive to varying redox conditions such as vivianite, siderite and ferric sulfides, jarosite are introduced with optical and electron microscope images, energy dispersive X-ray analysis, and X-ray diffraction.  Many examples are from paddy field soil because in the paddy fields, reducing conditions and oxidizing conditions are repeated every year.  The visual evidence of redox in the soil profile is iron mottles formed at the redox interface.  Elemental distribution of the iron mottles changes with morphological properties of the mottles.   It was revealed that an increase in the amount of available (acid soluble) phosphate in the reduced paddy field soil is mainly due to crystallization of vivianite.  However, the vivianite dissolves again with the development of oxidizing conditions after drainage passively due to lowering of ferrous ion activity.  Siderite is a ferrous carbonate mineral often found in the reduced subsoil.  An example of siderite found as an pseudomorph of tubular iron mottles is provided.  Oxidation of the large amount of pyrite results in formation of acid sulfate soil.  Pyrite found in the tsunami deposit 2011 and Jarosite from eastern coast of Australia are used as examples.   5.1 Redox reactions regarding soil minerals 5.2 Iron mottlings 5.3 Iron Phosphates 5.4 Siderite 5.5 Pyrite and related sulfur containing inorganic constituents   Chapter 6 Role of inorganic soil constituents in selected topics Three topics are provided to exemplify how the inorganic soil constituents play important roles.  They are effects of tsunami on soil in 2011, Japan, dynamics of radiocesium in soil environment and phosphorus cycling in soil-plant systems.  These topics include different interactions between the different inorganic soil constituents.  These topics are helpful to disaster prevention and sustainable food production.   6.1 Evaporites and Tsunami-affected soils Evaporites such as halite, gypsum, etc. are introduced.  Examples found on the surface of lahar deposit in Luzon island and soils affected by tsunami 2011, Japan are shown with optical and electron microscope images, energy dispersive X-ray analysis.  Then, an example of effects of seawater on agricultural soils is introduced based on analyses of deposits and soils at 344 sites.  By comparing soil map and distribution of the carbon content of the tsunami deposit, it was revealed that the muddy tsunami deposit was strongly affected by the nearby farmland soils.  At the well-drained sites, salts were removed with rain.  In contrast, an adverse effect of seawater lasts long in the coastal area due to the subsidence of the ground.   6.1.1 Evaporites 6.1.2 Effect of tsunami 2011 on agricultural soils 6.1.2.1 Properties of tsunami deposit 2011 6.1.2.2 Salinization, sodification and restoration   6.2  Radiocesium Cesium ion is strongly sorbed by inorganic soil constituents, and hardly moves in soil.  However, cesium ion can move with inorganic soil constituents when erosion take place.  The extractability of cesium ion from soil are described comparing with other alkaline metal ions.  Radiocesium affected soils of all over the world in 1950’-60’s due to atmospheric nuclear testing and it is still detectable in soil.  Further, a large amount of radiocesium deposited on soil by the accidents of nuclear power plants in Chernobyl (1986) and in Fukushima (2011).  Regarding the case in Fukushima, semi-micro and macroscopic vertical distribution of radiocesium in the Tsunami-affected soil and transportation of radio cesium in rivers are described.   6.2.1 Sorption of cesium ion by soil 6.2.2 Vertical distribution of radiocesium in soil 6.2.3 Transportation of radiocesium in rivers estimated from side bar deposits   6.3 Inorganic constituents related to phosphorus cycle in soil-plant systems Phosphate rock is one of the depleting resources. Phosphate rock is mainly processed to fertilizers and is applied to farmlands.  However, recovery of phosphate from soil by plants is generally low due to sorption of phosphate by soil.  On the other hand, the amount of phosphate in the heavily fertilized farmland is increasing and gradual release of phosphate from farmlands is concerned in order to avoid eutrophication of surface water.  It is important to improve phosphate efficiency in agricultural soil-plant systems.   Apatite is the naturally occurring phosphate.  Although the concentration of apatite in fresh volcanic ash is not low compared with other soils, phosphate react with active Al and Fe in volcanic ash soil that forms with weathering of volcanic ash.  A Procedure to find apatite particles in volcanic ash, SEM images and EDX spectra of apatite are introduced.  Then, reactions of phosphate ion with active Al and Fe materials are outlined including reactions of Ca phosphates with active Al and Fe materials.  Phosphate absorbed by agricultural plants is partly returned to farmlands as compost and manures.  Struvite is a major phosphate minerals found in swine and chicken manure composts.  Brassica plant roots cover particulate phosphate　such as brushite, struvite completely and show high efficiency in phosphate uptake especially in Andisols with high P fixation capacity.  Phosphate cycling in paddy fields is reviewed highlighting crystallization of vivianite under reducing conditions as shown above (5.3).   6.3.1 Apatite 6.3.2 Reactions of phosphates with active Al and Fe materials 6.3.3 Struvite and P foraging root growth 6.3.4 Phosphate cycling in paddy fields