Soil is an effective filter with three modes of action:

• physical - acts like a sieve to retain large particles which will not go through small pores
• chemical - cation exchange capacity retains some pollutants through exchange processes, also some chemicals are degraded through chemical reactions in/with soil
• biological - organisms biodegrade many pollutants applied to the soil

Phosphorus does not leach, but may be lost with soil and organic particles during erosion from the soil surface. Phosphorus is typically the most limiting nutrient in aquatic systems, so when it is added, aquatic plant life responds.

Eutrophication - enrichment of surface waters and ensuing algal growth, depletes oxygen, effects fish and other aquatic populations

The Chesapeake Bay was our first wake-up call. Now the greatest concern is the dead zone in the Gulf of Mexico, from the nutrients in the eroded topsoil from the Mississippi-Missouri River watersheds.

• pesticides and decomposition products (metabolites)
• inorganic - heavy metals
• organic - feedlots, food-processing plants, municipal and industrial wastes
• salts
• radionuclides
• acid rain

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• volatility - stability, ease of vaporization
• persistence- "lasting power" - degradation time measured in half-life - Table 18.5
• half-life - time required for 1/2 original amount of pesticide in soil to be deactivated
• solubility - ability to dissolve and mix with soil solution
• adsorption - held to soil, analogous to CEC
• partition coefficient - ratio of pesticide concentration adsorbed to that in solution phase

• reduce populations of disease vectors - mosquitos & yellow fever, malaria
• crop and livestock protection against pests (insects, weeds, etc)
• reduce spoilage of food

Classifications and common groups

• Insecticides
• chlorinated hydrocarbons
• organophosphates
• carbamates
• Fungicides
• historically - copper, mercury, arsenic -
• chlorothalanil - used in peanut production
• Herbicides - persistence varies
• Rodenticides
• Nematocides

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1. Vaporize into atmosphere without chemical change
2. Adsorbed by humus and clay particles
3. Leached in liquid or solution forms
4. Chemical reactions w/in or on soil surfaces
5. Degraded by microbes
6. Absorbed by plants, detoxified
7. Lost in runoff
8. Photodecomposition

• sewage sludge, industrial wastes: Zn, Cu, Ni, Cd, Pb
• others: As, Pb, B, Fl, Hg
• As is found in a common mineral (pyrite) in the Rocky Mountains, thus can be found in irrigation and drinking water in New Mexico
  

• Eliminate or reduce soil application (limit quantities applied, legislation)
• Limit cycling of the toxins
• Keep the chemicals in soil, not plants
• Modify pH (>7) to limit solubility
• Draining wet soils (swampbuster implications)
• Crop selection and harvest time

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• Domestic, farm, food/fiber processing wastes
• Industrial operations
• Disposal into surface waters and atmospheric emissions already regulated
• Soil can serve as a disposal site
• Appropriate quantities can improve physical and chemical properties
• Excess can increase pollution of surface and ground waters, make soils unproductive

• paper products, garbage, - both biodegradable, some paper products can be recycled
• glass, metals - non biodegradable but could be recycled
• often used as fill materials to create upland areas for parks or other facilities

• Leaching and runoff can occur from improperly designed facilities can contaminate both surface and ground waters
• Though many of the materials would degrade under the proper conditions, once in a landfill, they are covered. Once buried, the required microbial activity, oxygen, and moisture do not allow degradation to occur. Weiners have been found intact in core samples taken from landfills buried for 25 years. There should be options that allow nutrient recycling to occur.

• "Out of sight, out of mind."
• Commonly bury it or let it wash away with the river, ...
• "The solution to pollution is dilution."
• This works on small scales, but when large quantities of pollutants are released into water, the system is overloaded, and fails.

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• pH of rainwater 5.6, due to presence of H₂CO₃ formed from CO₂ in the atmosphere in industrial and densely populated areas (automobile intensive areas), pH of rain often near 4, and in extreme cases may be as low as 2.
• NO and SO₂ emissions from exhaust fumes or industrial: changed in the presence of light, atmospheric gasses and water into nitric (HNO₃), nitrous (HNO₂), and sulfuric (H₂SO₄) acid
• Over long term, decrease soil pH, application of lime can remediate effects to soil
• Extremely acid rain can limit plant growth, also is detrimental to buildings (especially brick and mortar), elimination of acid rain has political and economic implications

• Naturally occurring - ⁴⁰K, ⁸⁷Rb, and ¹⁴C
• Fission products (nuclear weapons testing) - ⁹⁰Sr, and ¹³⁷Cs
• Sr acts like Ca - adsorbed, CEC, plant uptake
• Cs becomes fixed in soil like K⁺, nonexchangeable
• Potter County radionuclides
  
• Radioactive wastes, buried
• plutonium, uranium, americium, neptunium, curium, cesium
• Vary in solubility, plant uptake, reactions in soil
• Radon gas: colorless, odorless, radioactive gas - causes lung cancer, soil serves as a channel, moving radon into basements with little air circulation
• Plants, soil, and remediation at Chernobyl