Exam IV

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Exam IV
Exam IV will be offered on Wed. Dec. 5 in class
It will also be offered during the regularly
scheduled time
Thursday, December 13th
Study Guide will be posted this afternoon
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A toxic neighbor
contaminated with a mix of wood-treating
chemicals
90-acre site
Gainesville Sun November, 30th
Tests show arsenic and dioxins in the soil at
levels exceeding state cleanup standards.
Dioxin ½ life in soils 10 30 years
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Organic Chemicals
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Dioxin
0.2 µg/L
PCB
10-31 µg/L (50 Cl)
DDT
insoluble
Principally carbon, hydrogen
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Improving Solubility
Organic Solvents
Soap/detergents
Structural similarity between the chemical and
the solvent.
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Lipids and Solubility
Structural similarity between the chemical and
the solvent.
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Solubility
A chemicals solubility in lipids or organic
solvents is inversely proportional to its
solubility in water.
(Carbon/hydrogen)
Carbon/hydrogen
water
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Consequences
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Bio-Accumulation
Water and phytoplankton to zooplankton 800 x
Overall 120,000 times original concentration
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PCBs
Spokane River
Nov. 2002
Smallmouth bass - 1100-1800 ppb    Round gobies
- 200-800 ppb    Zebra mussels - 100 ppb
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Toxaphene Biomagnification
Seawater
0.0003 ppb
Arctic cod muscle
14 - 46 ppb
Narwhal blubber
2440 - 9160 ppb
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Other Hydrocarbons
1972
1983
Chlordane Mirex DDT Dieldrin
Chlordane
DDT
Non-point source
Biomagnified
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Mirex
highest levels ever recorded in a living
organism.
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Quantification
How can soils help?
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An Important Organic Solvent Octanol
C8H18O
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The Octanol-Water Partitioning coefficient
C8H18O
Octanol and water are immiscible
Density 0.824 g/cm3
C8H18O
octanol
water
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Partitioning
Carbon/hydrogen
Octanol (Carbon/Hydrogen)
water
C10H20
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Add 10 mg chemical
1 L Octanol 1L Water
Analyze the water phase for the
chemical. Difference between initial amount and
amount in water amount in octanol The ratio
between the two yields the Kow
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Add 10 mg chemical
1 L Octanol 1L Waterl
9.99 mg L
0.01 mg L
9.99 mg L
Kow
999
0.01 mg L
Water phase
octanol phase
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Kow of some Organochlorine Compounds Dioxin 6
,000,000 PCBs 2,000,000 DDT
4,000,000 Dieldrin 158,000
Toxaphene 316,000
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What does this have to do with soils?
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Organic Matter
Carbon Hydrogen Oxygen
Coiled and convoluted chains of carbon, hydrogen,
and oxygen
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Organic Matter
Carbon Hydrogen Oxygen
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Partitioning/Distribution
Organic matter
Soil Solution
Absorption
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Turn 4 pages
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Quantifying Partitioning and Absorption in Soils
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Quantifying Absorption
1 Liter
100 mg/L
25 mg/g
Pesticide solution
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Distribution Coefficient
(mg/g soil) (mg/L solution)
Pesticide on soil Pesticide in solution
Kd
300 mL/g
Index for a given soil
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Two Soils
Same Pesticide
Kd (2) 60 mg/g 40 mg/L
Kd (1) 25 mg/g 75 mg/L
Kd (2) 1.5 L/g
Kd (1) 0.3 L/g
1500 mL/g
300 mL/g
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Organic Matter and Organic Carbon
Retention of organic chemicals is strongly
correlated with O.C. content
Organic matter 40 - 60 carbon
approximately
50 organic carbon
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Organic Carbon Distribution Coefficient
Kd
Koc
Fraction o.c.
3000 mL/g
3000 mL/g
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Koc of some Organochlorine Compounds PCBs
2,000,000 DDT 4,000,000 Dieldri
n 158,000 Toxaphene 316,000
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Modern Pesticides
Atrazine
Solubility 30 mg/L
Carbaryl
Solubility 40 mg/L
C
C
C
C
napthalene
Solubility 32 mg/L
C
C
C
C
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Practical Range for Some Modern Pesticides
Koc 2 6000 mL/g
Dicamba 2 Malathion 1800 Chlorpyrophos 6070
http//soillab.ifas.ufl.edu/cmis/
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http//soillab.ifas.ufl.edu/cmis/
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Summary

• Many organic compound are non-polar
• Non-polar compounds are weakly soluble in water
• Non-polar compounds are soluble in organic
  solvents.
• Organic matter can behave like an organic solvent
• Kow describes the distribution of a chemical
  between
• the organic solvent, octanol, and the soil
  solution.
• Koc describes the distribution of a chemical
  between
• soil organic carbon and the soil solution.
• Koc will impact the movement and distribution of
• organic chemicals in soils.
• Organic chemicals degrade. The ½ life is an
  indicator of
• the chemicals relative persistence.