Chapter_04_soil
合集下载
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
Chapter 4 - The Terrestrial Environment
Objectives: 1. Understand the terrestrial environmental from an integrated physical, chemical and biological perspective. 2. Define a surface soil, the vadose zone, and the saturated zone. 3. Define components of soil discussed in class such as texture, pore size distribution, organic matter, soil structure, interaggregate and intraaggregate pores, cation exchange, soil water potential. 4. Understand how soil water potential relates to microbial activity. 5. Understand the basics of contaminant sorption and microbial sorption. 6. Understand how microbial activity can influence the soil atmosphere. 7. Be able to describe the types, numbers, and relative activities of microbes found in surface soil, vadose zone, and saturated zone environments. 8. Discuss the respective competitiveness of the bacteria, actinomycetes, and fungi in soil.
In r g r g tep r s a e( m m ins e In a g g te p re sp c tea ge a oe p c to m iz ) tra g re a o ae
Polysaccharide secretion binding of clay particles
Fungi Soil aggregate
Physical entanglement
Cross-section
Clay Particles C Polysaccharide secretion Cell wall Fissure Fungal hyphae MicroNon perturbed clay environment = oriented, packed and glued clay 1 micron
Core molecules for organic humus
Humus has a three dimensional sponge-like structure that can absorb water and solutes in the water. Humus is only slowly utilized by soil organisms and has a turnover rate of 1 to 2% per year. In general soils with higher organic matter contents have higher numbers of microbes and higher levels of activity.
Surface to volume ratio (cm2/g)
50 450 10,000
Texture and pore size distribution
Clay texture Loam texture Sand texture
Number of pores
Number of poresFineC Nhomakorabeaarse
Fine
Coarse
Number of pores
Fine
Coarse
The amount of clay and organic matter in a soil influence the reactivity of that soil because they both add surface area and charge. Because large amounts of clay make the texture of the soil much finer, the average pore size is smaller. Similarly fluids like water move more easily through large pores, not because the water molecules are too large, but because there is less resistance to water movement through larger spaces. Pore size distribution is important when one considers movement of fluids and of microbes through a porous medium. Protozoa and bacteria will have difficulty moving through even sandy porous media.
Surface Soils
10 structure = soil particles + organic matter (humus) + roots + microorganisms
20 structure = aggregate or ped = stability
Humic-like substances secretion hydrophobic region Bacterial colonies Polysaccharide secretion - hydrophobic region binding of clay particles
Vadose zone Saturated zone shallow aquifers intermediate aquifers deep aquifers
Scale can range from 10 to 100’s of meters
Surface soils
Surface soil (unsaturated)
Pore size
5% of the mean pore diameter
20 um
0.6-20 um 0.02–0.6 um
Filtration is important when the size of the bacterium is greater than 5% of the mean diameter of the soil particles
Humus shares two properties with clay: it is highly charged and it has a large surface area to volume ratio.
The quantity of organic matter found in soil depends on climate. Soils found in temperate climates with high rainfall have increased levels of organic matter. Levels of organic matter found in soil range from essential no organic matter (Yuma, AZ) to 0.1% organic matter (Tucson, AZ) to 3 to 5% organic matter (midwest) to 20% organic matter (bogs and wetlands).
Soil aggregates are formed and stabilized by clay-organic complexes, microbial polysaccharides, fungal hyphae and plant roots. See Info Box 4.4 for a special case of aggregation, cryptobiotic crusts.
Organic Matter
The major input of organic matter in soil is from plant, animal, and microbial biomass. Humus is the ultimate product of degradation of organic matter. Humus is aromatic in character. This is because the humus backbone is derived from the heterogeneous plant polymer lignin which is less readily degradable than other plant polymers (cellulose and hemicellulose).
X
Vadose zone (unsaturated)
Capillary fringe (nearly saturated) Water table Spontaneous water movement
Saturated zone
Components of a typical soil
1) 45% mineral (Si, Fe, Al, Ca, K, Mg, Na) The two most abundant elements in the earth’s crust are Si (47%) and O (27%)
Mineral
Soil texture – this defines the mineral particle sizes that make
up a particular soil.
particle diameter range (mm)
Sand: 0.05 – 2 mm Silt: 0.002 – 0.05 mm Clay: 0.0002 – 0.002 mm
Soil aggregates are associated with relatively large inter-aggregate pore spaces that range from um to mm in diameter. Each aggregate also has intra-aggregate pore spaces that are very small, ranging from nm to um in diameter.
Bogs and wetlands
Organic matter > 20% Bogs cover 5 – 8% of the terrestrial surface
Why do peat bogs have very low microbial activity? (see Info Box 4.2)
Quartz = SiO2
Clay minerals are aluminum silicates
Nonsilicates = NaCl, CaSO4 (gypsum), CaCO3 (calcite)
2) 50% pore space
3) 1 to 5% organic matter
OM
Pore space
Objectives: 1. Understand the terrestrial environmental from an integrated physical, chemical and biological perspective. 2. Define a surface soil, the vadose zone, and the saturated zone. 3. Define components of soil discussed in class such as texture, pore size distribution, organic matter, soil structure, interaggregate and intraaggregate pores, cation exchange, soil water potential. 4. Understand how soil water potential relates to microbial activity. 5. Understand the basics of contaminant sorption and microbial sorption. 6. Understand how microbial activity can influence the soil atmosphere. 7. Be able to describe the types, numbers, and relative activities of microbes found in surface soil, vadose zone, and saturated zone environments. 8. Discuss the respective competitiveness of the bacteria, actinomycetes, and fungi in soil.
In r g r g tep r s a e( m m ins e In a g g te p re sp c tea ge a oe p c to m iz ) tra g re a o ae
Polysaccharide secretion binding of clay particles
Fungi Soil aggregate
Physical entanglement
Cross-section
Clay Particles C Polysaccharide secretion Cell wall Fissure Fungal hyphae MicroNon perturbed clay environment = oriented, packed and glued clay 1 micron
Core molecules for organic humus
Humus has a three dimensional sponge-like structure that can absorb water and solutes in the water. Humus is only slowly utilized by soil organisms and has a turnover rate of 1 to 2% per year. In general soils with higher organic matter contents have higher numbers of microbes and higher levels of activity.
Surface to volume ratio (cm2/g)
50 450 10,000
Texture and pore size distribution
Clay texture Loam texture Sand texture
Number of pores
Number of poresFineC Nhomakorabeaarse
Fine
Coarse
Number of pores
Fine
Coarse
The amount of clay and organic matter in a soil influence the reactivity of that soil because they both add surface area and charge. Because large amounts of clay make the texture of the soil much finer, the average pore size is smaller. Similarly fluids like water move more easily through large pores, not because the water molecules are too large, but because there is less resistance to water movement through larger spaces. Pore size distribution is important when one considers movement of fluids and of microbes through a porous medium. Protozoa and bacteria will have difficulty moving through even sandy porous media.
Surface Soils
10 structure = soil particles + organic matter (humus) + roots + microorganisms
20 structure = aggregate or ped = stability
Humic-like substances secretion hydrophobic region Bacterial colonies Polysaccharide secretion - hydrophobic region binding of clay particles
Vadose zone Saturated zone shallow aquifers intermediate aquifers deep aquifers
Scale can range from 10 to 100’s of meters
Surface soils
Surface soil (unsaturated)
Pore size
5% of the mean pore diameter
20 um
0.6-20 um 0.02–0.6 um
Filtration is important when the size of the bacterium is greater than 5% of the mean diameter of the soil particles
Humus shares two properties with clay: it is highly charged and it has a large surface area to volume ratio.
The quantity of organic matter found in soil depends on climate. Soils found in temperate climates with high rainfall have increased levels of organic matter. Levels of organic matter found in soil range from essential no organic matter (Yuma, AZ) to 0.1% organic matter (Tucson, AZ) to 3 to 5% organic matter (midwest) to 20% organic matter (bogs and wetlands).
Soil aggregates are formed and stabilized by clay-organic complexes, microbial polysaccharides, fungal hyphae and plant roots. See Info Box 4.4 for a special case of aggregation, cryptobiotic crusts.
Organic Matter
The major input of organic matter in soil is from plant, animal, and microbial biomass. Humus is the ultimate product of degradation of organic matter. Humus is aromatic in character. This is because the humus backbone is derived from the heterogeneous plant polymer lignin which is less readily degradable than other plant polymers (cellulose and hemicellulose).
X
Vadose zone (unsaturated)
Capillary fringe (nearly saturated) Water table Spontaneous water movement
Saturated zone
Components of a typical soil
1) 45% mineral (Si, Fe, Al, Ca, K, Mg, Na) The two most abundant elements in the earth’s crust are Si (47%) and O (27%)
Mineral
Soil texture – this defines the mineral particle sizes that make
up a particular soil.
particle diameter range (mm)
Sand: 0.05 – 2 mm Silt: 0.002 – 0.05 mm Clay: 0.0002 – 0.002 mm
Soil aggregates are associated with relatively large inter-aggregate pore spaces that range from um to mm in diameter. Each aggregate also has intra-aggregate pore spaces that are very small, ranging from nm to um in diameter.
Bogs and wetlands
Organic matter > 20% Bogs cover 5 – 8% of the terrestrial surface
Why do peat bogs have very low microbial activity? (see Info Box 4.2)
Quartz = SiO2
Clay minerals are aluminum silicates
Nonsilicates = NaCl, CaSO4 (gypsum), CaCO3 (calcite)
2) 50% pore space
3) 1 to 5% organic matter
OM
Pore space