Soils and the Environment

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

Chemical Weathering Alteration (e.g, feldspar to clay+quartz) Dissolution

Chemical Weathering Reactions

Soil Profile Development Variables: Parent material Climate Topography Time (Soil age / extent of development) Organic activity

Soil Horizons

Climatic Effects on Soil Formation

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) Depends on relative proportions of sand-, silt, -clay sized particles

Soil Structure Aggregates of soil particles = peds Peds classified by shape (structure)

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

Cycles / Systems Associated With Soils

Soil Classification Soil Taxonomy Engineering Classification (See Table) Engineering Classification

Engineering Properties of Soils Soil phases Solid material Liquid 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 Equation A = 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)

Soil Erosion due to diversion of runoff water

Land Use & Other Soil Problems Urbanization Off-Road Vehicles Soil Pollution Desertification Others

Effects of land use on sediment yield; with sharp peak during construction & urbanization

Off-road vehicle excavation Urbanization erosion

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

Extent of desertification of arid lands of the world

Land Use & Other Soil Problems Urbanization Off-Road Vehicles Soil Pollution Desertification Others Swelling & shrinking Acid mine waters

Swelling & Shrinking of Soil Minerals

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 Pollution abatement Others? Terracing, contour stripping Vegetation barriers Water/sediment basins/reservoirs Characterization & planning Pollution abatement Treament, e.g., bioremediation Others?

Storm water sediment basin

Summary/Overview Definitions of soil Variables (explain) 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