Chapter 1 Soil Mineral Material
Section 1 The chemical and mineral constitutes of soil parent
minerals
一, The chemical constitutes of soil parent minerals
Soil
Mineral Material
38%,(95%)
Organic matter
12%,(5%)
Solution
(15-35%) Air
(15-35%)
表 1 - 1 地壳和土壤的平均化学组成 (重量 % ) (维诺格拉多夫,1950, 1962 )
*
元 素 地壳中 土壤中 元 素 地壳中 土壤中
O
Si
Al
Fe
Ca
Na
K
Mg
Ti
H
47.0
29.0
8.05
4.65
2.96
2.50
2.50
1.37
0.45
(0.15)
49.0
33.0
7.13
3.80
1.37
1.67
1.36
0.60
0.40
Mn
P
S
C
N
Cu
Zn
Co
B
Mo
0.10
0.093
0.09
0.023
0.01
0.01
0.005
0.003
0.003
0.003
0.085
0.08
0.085
2.0
0.1
0.002
0.005
0.0008
0.001
0.0003
* 根据克拉克等 (1924),费尔斯曼 (1939) 和泰勒 (1964) 的估计,地壳的化学元素组成与此表稍有不同,但总
的趋势是一致的。
Distributive law
( 1) The oxygen( O) and silicon( Si) are main two
elements in the earth crust,The second elements are iron
and aluminum,Four elements occupy about 88.7%
weight of the earth crust,
( 2) The essential elements for plant growing are very
low and distribute unbalance in earth crust.
二,The mineral constitutes in the soil
According to the crystallize
appearance of the mineral,
the mineral can be divided
into:
Crystallization mineral
and no-crystallization
mineral
According to the source of
the mineral,the mineral can
be divided into,
Primary mineral and
secondary mineral
二,The mineral constitutes in the soil
Primary mineral formed from cooling the molten(lava) rock.
① The silicate and aluminosilicates are main compositions
in the primary mineral.
② The feldspar and quartz are main mineral in the primary
mineral.
③ The primary mineral is an important source of the plant
nutrient,
Relationship between soil particles and the mineral types
Section 2 Clay Mineral
Clay minerals are mostly newly formed crystals reformed
from the soluble products of the primary minerals and
may be considered secondary minerals.
一,Layer silicate clay mineral
(一) Structure characteristics
1,Basic construction unit
(1) Basic Building Blocks for Clay
Minerals
Silicon - Oxygen Tetrahedron (Si2O5-2)
Basic Building Blocks - 2
Aluminum Octahedral (Gibsite Sheet)
Al(OH)6-3
Silicate Clay Minerals
? Aluminosilicates have a definite
crystalline structure,Formed by the
alteration of existing minerals or by
synthesis from elements.
? <,002 mm in size (only seen with aid
of electron microscope)
? Two basic kinds of clay minerals
1, 1 and 2, 1
(2) Types of Clay Minerals
1) Kaolinite a 1,1 clay mineral
1 silica sheet and 1 gibsite sheet
.0072 cm thick
2, 1 CLAY MINERALS
1,Hydrous Mica or Illite
replacement of Si4+ with Al3+ in 25% of
tetrahedrals,each substitution leaves 1 neg
charge site also K+ ions are a bridge between
layers and hold them tightly together
K Space
2,Montmorillonite
Mg++ replaces Al+++ in Octahedral
layer
3.Unit crystalline layer
2:1:1 Clay minerals
A layer of
chlorite has 2 silica
tetrahedra,an
alumina octahedra,
and a magnesium
octahedra sheet,
They are often called
2:2 or 2:1:1 type Clay
minerals
4,Isomorphous Substitution
Isomorphous Substitution is the
substitution of one ion for
another of similar size but low
positive valence.
E,g,Al3+ for Si4+ or
Mg2+ for Al 3+
The regulation of Isomorphous Substitution in soil:
1,Notice that most substitutions are by
ions with lower charge (less positive) than
the ones being replaced.
2,The total negative charge from the
anions (the oxygens) remains unchanged,but
lower positive charge because of
substitution results in an excess negative
charge at that general site.
(二),Types and general
characteristics of silicate clay minerals
Four groups:
Kaolinit
Montmorillonite
Hydrous mica (illite)
Chlorite
Properties:
(1) 1:1 type
( 2) Almost no substitution of Al3+ for Si4+,or Mg2+ for
Al3+ has occurred in kaolinite,so the net negative charge
is low.
( 3) It does not shrink and swell.
( 4) The colloidal characteristics are weaker.
Kaolinit group is in moist,warm to hot,subhumid and
humid leached soils.
Kaolinit group
Mineral construction of Kaolinit group
Properties:
( 1) 2:1 type
( 2) Large expansion
( 3) Isomorphous substitution is common in
Montmorillonite,which has most of charge.
( 4) The colloidal characteristics are strong.
Montmorillonite group
Montmorillonite group is in arid to humid
soils having limited leaching.
Mineral construction of Montmorillonite group
Properties:
( 1) 2:1 type
( 2) non-expanding
( 3) Large potassium ions holding
adjacent layers together
( 4) Slight to moderate swelling
Hydrous mica (illite) group
Hydrous mica (illite) group is subhumid and
cool areas,parent rock with micas.
Mineral construction of Hydrous mica (illite) group
Chlorite group
This group previously formed in marine sediments.
Properties:
( 1) 2:2 or 2:1:1 type Clay minerals
( 2) Without swell
( 3) Low cation exchange capacities
二,Sesquioxide clays
(metal oxides and hydrous oxides)
(一) iron oxide (Fe2O3)
Goethite( a-FeOOH)
Hematite( a- Fe2O3 )
These clays can be either amophous or crystalline,
They do not swell,are mot sticky,and do not
behave as do the silicate clays.
Iron oxide and iron hydrate commonly color the
soils various shades of red to yellow,respectively.
(二) Aluminum hydroxide (Al(OH)3 or
Al2O3·xH2O)
(三 ) Allophane (xAl2O3·ySiO2·nH2O)
(四 ) Silicon oxide
1、风化递变学说
白云母经风化很容易形成水化云母,随着风化和淋溶程
度的发展,云母类型矿物可能依次顺着伊利石、蛭石、蒙脱
石、高岭石以至三水铝石的方向递变。
第三节 我国土壤粘土矿物分布规律
一、风化和成土作用与粘土矿物组成的关系
粘土矿物也可能不是直接从原来的矿物变过
来的,而是由化学风化所分离出来的简单风化产
物在一定条件下重新组合沉淀而成。即:
2、风化合成学说 (自然合成说)
结晶态粘土矿物老化
SiO2·nH2O Al2O3·nH2O
Fe2o3·nH2O
酸胶基 + 碱胶基 非结晶态粘土矿物
二、我国土壤粘土矿物分布规律
(一)水云母区 包括新疆、内蒙古高原西部、柴达木盆
地、青藏高原大部。土壤粘土矿物以水云母为主,其次为
蒙脱石和绿泥石。
(二)水云母-蒙脱石区 包括内蒙古高原东部、大小
兴安岭、长白山地和东北平原大部分。土壤粘粒中蒙脱石
明显增多。
(三)水云母-蛭石区 包括青藏高原东南边缘山地、黄
土高原和华北平原。西部山地土壤粘粒中绿泥石,东部多
蛭石,华北平原土壤粘粒中蒙脱石也不少。
(四)水云母-蛭石-高岭区 包括秦岭山地和长江
中下游平原,为一狭长的过渡地带,在适宜条件下,水云
母、蛭石和高岭石都可成为土壤粘粒中的主要成分。
(五)蛭石-高岭区 包括四川盆地、云贵高原、喜
马拉雅山东南端。土壤粘粒中云母退居次要成分,以蛭石
和高岭为主。东部蛭石尤多,并多三水铝石;西部蛭石较
少,氧化物含量很 高,山地土壤中水云母含量随海拔高
度升高而增加。四川盆地土壤中还有不少蒙脱石。
(六)高岭-水云母区 包括浙、闽、湘、赣大部和
粤、桂北部。土壤中粘粒部分结晶差的高岭石为主。东部
不少水云母和蛭石伴存,铁铝氧化物含量也显著增多。
(七)高岭区 包括贵州南部、闽粤东南沿海、南海诸
岛及台湾。
二、我国土壤粘土矿物分布规律
本章小结
本章的主要内容是土壤矿物质的组成及粘
土矿物的结构与性质。
真章的重点是粘土矿物的结构和性质,认
真理解和掌握粘土矿物的结构和性质对学
习好以后各章有重要的作用。可以帮助你
正确理解土壤的许多理化性质。
主要掌握几种代表性的粘土矿物。
1、
2、
3、
1,砂质土全部由砂粒所组成, 粘质土全部由粘粒所组成
( )。
2,在同一地区, 土壤质地愈粘, 则养分含量愈多 ( )
3.南方红, 黄壤中的粘土矿物以高岭石为主, 而北方土壤
中以蒙脱石, 伊利石为主 ( )。
4.母质是形成未来土壤的岩石, 矿物的风化产物 ( )也是
搬 运后形成的地面沉积体 ( )
5,不同土壤类型粘土矿物的组成不同 ( )。
课堂速测
式中 X表示补偿异价离子置换引
起的电荷亏缺的层间可交换阳离
子。
6,农业土壤土体的底土层就是指的母质层 ( )。
7,任何土壤的矿物质组成中既含有原生矿物,也含有次生矿物
( )。
8,土壤矿物质的化学组成,一般 N素含量很少 ( )。
9,土壤中的粘粒均由次生矿物所组成并多以云母为主 ( )。
10.蒙脱石矿物晶架的顶,底层由离子键相连 ( );高岭石矿
顶、底层由氧键相连 ( );伊利石矿物则由 Si-O相连 ( )。
课堂速测