Erosion Contamination

1. September 22, 2008 Erosion & Contamination

2. What is Soil? Soil – unconsolidated porous media compromised of inorganic (clay minerals and oxides) and organic components (organic matter) Modified over time by physical, chemical, and biological agents Has distinct physical, chemical, and biological properties. Soil is dynamic.

3. Midwest Ag Soils Typically fertile, but poorly drained Drainage is facilitated by networks of artificial, subsurface drains to enhance productivity, about 1 m below the soil surface can rapidly move excessive soil water (and associated constituents) to surface waterways Preferential flow paths to tile drain systems develop reducing the effects of soil attenuation on transport.

4. Sediment movement Last week we discussed some benefits and problems with sediment movement: + nourishes floodplain farm fields, creates deltas and islands, and replenishes wetlands. – loss of excessive amounts of soil from cropland, urban construction sites, logging, etc. due to greatly increased erosion, soil fills lakes and reservoirs, obstructs shipping channels, clogs hydroelectric turbines, and requires more purification of water. Plusses – nourishes floodplain farm fields, creates deltas and islands, and replenishes wetlands. Minuses – loss of excessive amounts of soil from cropland, urban construction sites, logging, etc. due to greatly increased erosion, soil fills lakes and reservoirs, obstructs shipping channels, clogs hydroelectric turbines, and requires more purification of water. Plusses – nourishes floodplain farm fields, creates deltas and islands, and replenishes wetlands. Minuses – loss of excessive amounts of soil from cropland, urban construction sites, logging, etc. due to greatly increased erosion, soil fills lakes and reservoirs, obstructs shipping channels, clogs hydroelectric turbines, and requires more purification of water.

5. Erosion Erosion - the wearing away of the land surface by rain or irrigation water, wind, ice or other agents that abrade, detach and remove soil from one point on the earth's surface and deposit it elsewhere. (Glossary of Soil Science Terms. Soil Sci. Soc. Am. 1997) Soil erosion is a global problem. Erosion of soil can contribute to instability in a region because of inability to produce adequate food and fiber. In the U.S., the cost of water and wind erosion each year is estimated in billions of dollars. This high cost is attributed to erosion removing the upper soil layer from lands and subsequently reducing their productivity and polluting water and air.

6. Impacts of erosion on soil quality Organic matter (OM) contributes to soil productivity through its effect on the physical, chemical, and biological properties of the soil. Organic matter is a small fraction (2% to 4%) of soil mainly present on the soil surface. Erosion gradually depletes organic matter and decreases soil productivity.

7. Effects of a Loss of Organic Matter Soils tend to lose their physical structure. This makes the soil hard, compact and cloddy. Soil aeration (water-holding capacity and permeability) are decreased. Decreased aeration means less oxygen available for plant roots to grow and less water available for healthy plant growth. When soil permeability decreases, less water will soak into the soil and more will run-off. Beneficial organisms that suppress disease and break down organic residues will not function well due to reduced oxygen and water in soil. This in turn will reduce nutrient storage and supply abilities of the soil.

8. Impacts of erosion on air quality Soil particles blown by the wind into the air have a major impact on human and animal health. Particles suspended in air by wind are easily inhaled and accumulate in lung tissues causing major respiratory problems. Concentrated levels of wind blown particles can also reduce visibility and increase the risk of automobile accidents.

9. Factors Contributing to Soil Erosion Work on your own, or with someone to list all the factors that you can think of that contribute to Water erosion – Wind erosion –

10. Factors Contributing to Water and Wind Erosion of Soil

11. How Do These Factors Affect Erosion? Climate Soil Properties Texture Aggregation Soil Moisture Soil Cover Topography Land Management Irrigation practices Mechanical disturbance Soil Surface Roughness Unsheltered Distance Wind Velocity and Turbulence

14. Erosion – Tillage Tillage Management: A tillage system that buries residue and pulverizes soil leads to high erosion risk. A tillage system that preserves surface residue and minimizes soil disturbance causes less erosion.

15. Tillage Practices Tillage practices can be divided into "conventional" and "conservation" tillage. Conventional tillage creates more soil disturbance and mixing. Conservation tillage reduces soil disturbance to a minimum and keeps more residue from the previous crop at the soil surface.

17. Potential Farm Contaminants Pesticides Fuels (gasoline, diesel) Solvents (used to wash machine parts, etc.) Hormones and antibiotics (through manure) Suite of chemicals from junk piles

18. Contaminant Fate Processes Sorption/desorption Transformation (microbial, abiotic) Volatilization Rainfall, water flow, mixing Preferential transport Soil run-off Wetting/drying depostion

19. What is Sorption? Sorption is the transfer of a chemical to a soil. Desorption is the chemical transfer from soil to a solution or biota (all the plant and animal life).

20. Why Do We Care? Sorption moderates concentration in the solution phase, thus accumulation, attenuation, mobility, bioavailability, bioaccumulation Important process to consider in protecting your local water resources – ditches/streams, lakes/ponds, wetlands, groundwater, drinking water Sorption; therefore, is important in assessing potential risks to the environment and human health

21. Legacy Chemicals Arsenic – used for cattle dipping DDT Pesticide banned in the 1973 Highly sorbed and persistent especially in an aerobic environment Flooding farmland to regain wetlands sometimes releases DDT PCBs – from trashed transformers Paints – metals (Pb, Cr) and organic bases (amines) Solvents – petroleum based or chlorinated solvents dense nonaqueous phase liquids, thus unpredictable

22. Facilitated Transport (not predicted by sorption) Preferential flow (e.g., macropores) Facilitated transport of chemicals bound to mobile colloids (soil or manure) may be a major contributing factor in transport to surface and groundwater. Runoff

23. Chemical Degradation Factors Abiotic and/or microbial Soil Type Moisture Content Temperature Nutrients Compound concentrations Presence of other compounds Residence Time (longer time, greater time for degradation)

24. Land-applied Manure Antibiotics Generally large in size with a high affinity for the soil Usually antibiotic soil concentrations are low and below levels that would cause any problems Biggest issue for antibiotics – excretion of antibiotic- resistant bacteria and transfer potential of genetic information to other bacteria and human pathogens Hormones Much more of a concern as they can invoke negative effects to aquatic communities at low levels!

25. Animal Wastes Land Application Lagoon effluent irrigation (fixed or towable pivot systems) Broadcasting dairy/beef solids or spreading liquid manure slurries Subsurface injection(primarily swine manure from manure pits) Decision of which field to spread animal wastes are usually controlled by the nitrogen needs of the crops being grown.

26. Fate of Antibiotics & Hormones in Ag Antibiotics and hormones (natural & synthetic) in livestock production: 10.3 million lbs/yr in hogs 10.6 million lbs.yr in poultry 3.7 million lbs/yr in cattle (Humans: 3 million lbs/yr) Estimated hormone excretion by farm animals (Lange et al., 2000): Androgens 4.4 tons Estrogens 40 tons

27. Tile Discharge Flow Water from field tiles can contain nutrients, primarily nitrates pesticides and other active ingredients (such as surfactants) a low amount of phosphorus … especially the first month after application If tile-fed pond water is to be used only for irrigation purposes, the recycled nutrients and pesticides in the drainage water should not pose a problem in the Midwest. In arid areas with higher evaporation, salt buildup in the water could occur because of higher evaporation and less dilution from rainfall.

28. Can you name the erosion control measures pictured?

32. Urban Erosion Control Vegetative cover – maintained or planting new Mulching to cover bare soil Silt fences Gravel access paths Impoundments Detention ponds