Soil / Groundwat er Pollution & R emediation 1 Soil Environmental Chemistry Chapter 15 & 16* • Why soil environmental chemistry is important? – The place where food and energy source are produced (agriculture/mining) – The dumping ground of municipal refuse, hazardous waste (landfill) and radioactive waste (Section 15.21) – Source of drinking water (groundwater) (Section 15.9) – Soil pollution is related to air pollution and water quality (Section 15.19, 15.20) ***Skip Sections 15.3 -15.5, 15.10 - 15.17 & Sections 16.9-16.11
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Soil / Groundwater Pollution & Remediation
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Soil Environmental ChemistryChapter 15 & 16*
• Why soil environmental chemistry is important?– The place where food and energy source are
produced (agriculture/mining)– The dumping ground of municipal refuse, hazardous
waste (landfill) and radioactive waste (Section 15.21)
– Source of drinking water (groundwater) (Section 15.9)
– Soil pollution is related to air pollution and water quality (Section 15.19, 15.20)
Scope of Soil Chemistry• Geosphere, or solid earth, is that part of earth upon which
humans live and from which they extract most of their food, minerals, and fuels
• Lithosphere is part of the geosphere that is directly involved with environmental processes through contact with the atmosphere, the hydrosphere, and living things (p. 2-3)
– Protect plant nutrient from leaching (Ca2+, K+, Mg2+) (soil clay is negatively charged due to ion replacement of Si4+ and Al3+ by metal ions of similar size but less charge): [SiO2] + Al3+ [AlO2
-] + Si4+ (p. 131) the reason why soil has cation exchange capacity (CEC)
– Can be a pollutant carrier in water (e.g., clay adsorbs metals)
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Soil Pollution
• Major soil pollutants– Heavy metals– Pesticides– Fertilizers (N, P)
• Process by which organic hazardous materials are biologically degraded, usually to innocuous materials such as carbon dioxide, water, inorganic salts and biomass (biotransformation and mineralization)
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Bioremediation Market Assessment• 100 million tons of hazardous waste generate annually• One third of over 2 million gasoline UST’s are leaking• Over 50,000 historically contaminated sites• All federal installations require extensive remediation
action• Estimated cost of $1,700,000,000,000• EPA consider bioremediation the lowest cost treatment
where applicable
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When Does Biodegradation Occur?
• When proper conditions exist
• When appropriate metabolic activity is expressed
• When there is “contact” between contaminants, nutrients, and organisms
• When toxicity or preferential utilization does not occur
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Natural Attenuation
• Natural assimilative capacity
• Process by which the indigenous microflora degrades contaminants using ambient levels of nutrients and electron acceptors
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Phytoremediation
• Process by which inorganic and organic contaminants are uptaken by vegetation (plants) from contaminated soils. Plants are then removed by biomass (p.492)
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ContaminatedSoil
TumblingBarrel
Sieve
SoilWashing Unit
Sievings
SlurryTank Emico Slurry Reactors
EffluentHolding Tank
Coagulant(CaCl2)
pH1. Nutrients2. HCl3. NaOH4. Compressed Air
Recycled water (optional)
Effluent Solids
Washed Soil
Supplemental Water
Soil Wash1 2 3 4
5. Air-Lifter6. Air Diffusers7. Bottom Rakes8. Foam Breaker
5
6
8
7
Soil Slurry Reactor (Zhang et al., 2000)
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Environmental Chemistry• The study of the sources, reactions,
transport, effects, and fates of chemical species in water, soil, air, and living environments, and the effects of technology thereon