soils and the environment. learning objectives soils terminology & processes interaction of...
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Learning Objectives
• Soils terminology & processes• Interaction of water in soil processes, soil
fertility• Classification of soils (familiarity)• Engineering properties of soil• Relationships between land use and soils• Sediment pollution• Desertification
• How/why is soil important in environmental geology?
• What is soil? Definition(s)?
• How does soil form?
• How does chemical weathering work?
• What is the significance of mechanical weathering?
• Factors/parameters that affect soil formation?
• What is a “soil profile”?
• What are soil horizons? Types?
• What effect(s) does climate have on soil formation? Examples?
• What are the three main types of soil properties?
• What is the significance of “categorizing” soils by these properties?
• How are soils identified by texture?
• How are soils identified by structure?
• What other types of soil properties are there? Explain
• How/where do soils fit into natural cycles/systems
– in terms of interactions with atmosphere, hydrosphere, etc.?
– in terms of e.g., the nitrogen cycle?
• How are soils classified? Significance?
• Distribution/examples of soil classification?
• What are soil phases?
• What are the “engineering properties” of soil? Significance?
• What is the soil/erosion loss equation? How used? Significance?
• What is sediment pollution?
• How do human activities affect soils?
• What are the main problems associated with soils?
• How do the following affect soils?
• - Urbanization
• - Off-road vehicles
• - Land use
• - Soil pollution
• What is desertification? What are the driving forces? Explain
• What factors affect desertification?
• Where do deserts occur? Where is desertification occurring? Significance?
•
• What is the significance of swelling/shrinking of soils?
• What is the significance of acid mine drainage on soil?
• What are soil surveys? Explain
• What are some types/examples of corrective measure used to address problems
associated with soils?
The word "soil" means different things to different people
• Farmers: – That part of the earth's surface
contained decayed and organic material in sufficient quantity to grow plants and crops.
• Geological: – Unconsolidated, unlithified residual
(left over) material from underlying parent rock which supports root growth
• Soil Science:– Altered solid earth material that can
support rooted plant life
• Engineering:– Solid earth material that can be
moved without blasting
Roles of Soils in the Environment
• Land use planning (suitability)– Soil erosion– Agriculture– Construction
• Waste management (interactions between waste, soil, water)
• Natural hazards: land use planning in terms of:– Floods– Landslides, slope stability– Earthquakes
Soil Formation• Soil formation begins with weathering• Weathering: Physical and/or chemical breakdown
of rocks (open system):– Physical (mechanical) Processes: Big ones to little ones
• Abrasion• thermal (expansion/contraction)• frost wedging
– Chemical Processes: Dissolution & alteration (congruent vs. incongruent dissolution w/residue)
• Soil Formation depends on:– Climate– Topography– Parent material– Time/age of soil– Organic processes
Physical Weathering• Making big pieces into smaller pieces
– increases surface area available for chemical weathering
Soil Profile Development
Variables:– Parent material – Climate– Topography– Time (Soil age / extent
of development)– Organic activity
Soil Properties/Indicators
• Color– Dark: indicative of organic material (O, A horizons) or
iron– Light:
• Whitish: Indicative of leaching (E-horizon)– Extensive leaching of iron, Al– Presence of carbonates
• Yellow, brown, red (B-horizon)
– Be careful (e.g., basaltic material, volc. ash)
• Texture (particle size)• Structure
Soil Texture (particle size)
Soil Texture: –Depends on relative proportions of sand-, silt, -clay sized particles
Other Soil Features/Characteristics
• Relative profile development– Weakly developed
– Moderately developed
– Well developed
• Soil Chronosequences– Arrangement from youngest to oldest
– Significance? When needed or used? (see fig.)
– How determined (if not obvious)?
More Soil Features/Characteristics
• Soil Fertility– Definition: Capacity of soils to supply nutrients
(N, P, K)– Significance?
• Water in Soils– Soil moisture
• Saturated• Unsaturated
– Significance?
Engineering Properties of Soils
• Soil phases1. Solid material
2. Liquid
3. Gas
• Soil Properties– Placsticity– Soil strength– Cohesion– Friction– Sensitivity– Compressibility– Erodibility– Permeability– Corrosion– Ease of excavation– Shrink-swell potential
Soil Erosion/Loss
• Loss of volume, mass, or weight of soil from a location in a specified time and area e.g., kg/yr/hectare
• Universal Soil Loss EquationA = RKLSCP
• Significance (of factors & result)?
A = long-term avg. annual soil loss for the site
R = long-term rainfall runoff erosion
K = Soil erodibility index
L = Hillslope/length factor
S = Hillslope/gradient factor
C = Soil cover factor
P = Erosion-control practice factor
Sediment Pollution:Sediment (eroded soil) as a pollutant
How is soil pollution a negative resource?
– Depletes useable soil– Reduces quality of water it enters– Deposition of sterile materials
Control/Reduction: Techniques, Examples (see text)
Figure
Land Use & Other Soil Problems
• Human activities affect soils by influencing patterns, amounts, and intensity of:– Surface-water runoff– Erosion– Sedimentation– Conversion/manipulation of natural areas &
surface water(see Figures 3.12, 3.13)
Land Use & Other Soil Problems
• Urbanization
• Off-Road Vehicles
• Soil Pollution
• Desertification
• Others
Land Use & Other Soil Problems
• Urbanization
• Off-Road Vehicles
• Soil Pollution
• Desertification
• Others
Land Use & Other Soil Problems• Urbanization• Off-Road Vehicles• Soil Pollution• Desertification
Driving Forces:
• Overgrazing
• Deforestation
• Soil erosion
• Poor irrigation drainage
• Overdraft of water supplies
• Off-road vehicle erosion
Desertification Factors:•Declining water table
•Salinization of soil & near-surface water
•Enhanced soil erosion (wind and/or water)
•Damage to native vegetation
Land Use & Other Soil Problems
• Urbanization
• Off-Road Vehicles
• Soil Pollution
• Desertification
• Others– Swelling & shrinking– Acid mine waters
Soil Surveys & Land Use Planning
• Descriptions
• Soil Maps (types, extent, properties)
• Information for identifying potential problems/issues BEFORE use (e.g., construction)
Corrective Measures
• Erosion Controls– Terracing, contour stripping– Vegetation barriers– Water/sediment basins/reservoirs– Characterization & planning
• Pollution abatement– Treament, e.g., bioremediation
• Others?
Summary/Overview• Definitions of soil• Roles of soils in
environmental geology– Land use planning
– Waste disposal
– Evaluation of natural hazards
• Formed from rock interactions in the hydrologic cycle (explain)
• Variables (explain)– Climate– Topography– Parent material– Time– Organic activity
• Soil processes form distinctive layers (horizons)
• Soil Properties:– Color– Texture (particle size)– Structure (peds)
Learning Objectives
• Soils terminology & processes• Interaction of water in soil processes, soil fertility• Classification of soils (familiarity)• Engineering properties of soil• Relationships between land use and soils• Sediment pollution• Desertification
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