Water Solubility

Transcription

Water Solubility
Organic Chemicals and
Water
Synthetic Organic Chemicals
Principally Carbon, Hydrogen and Oxygen
Organochlorines
Dioxins
Pesticides
Chlordane
Dioxin
PCBs
Cleaning agents
DDT
PBDE
Flame Retardants
Potential Toxicity
July
November
2004
Viktor Yushchenko
Ukrainian President
6,000 times the usual concentration in his body
the second highest dioxin level ever measured in a human
Water Solubility
Organochlorines as well as many other synthetic
organic compounds are poorly soluble in water
NaCl
Na+ + Cl-
Dioxin
Dioxin
0.2 µg/L
PCB
10-31 µg/L
(50% Cl)
Sodium Chloride
350 g/L
Potassium Chloride 280 g/L
Ionic compounds are about 1 billion times more water soluble than neutral organics
Improving Solubility
Organic Solvents
Soap/detergents
Structural/chemical similarity between
the chemical and the solvent.
Hexane
Lipids and Solubility
Structural/chemical similarity between
the chemical and the solvent.
Solubility
A chemical’s solubility in lipids is inversely
proportional to its solubility in water.
Lipid (Carbon/hydrogen)
Carbon/hydrogen
water
Toxaphene Biomagnification
Seawater
Arctic cod
muscle
Narwhal
blubber
0.0003 ppb
14 - 46 ppb
2440 - 9160 ppb
BAF = 8 million
What’s been done?
PCBs
used extensively in electrical equipment, especially transformers
Solubility: 10-31 µg/L
PCBs, valued for chemical stability
and fire resistance, were
manufactured and processed primarily
for use as insulating fluids and
coolants in electrical equipment
and machinery from 1929-1977.
Electrical equipment
plasticizers in paints,
plastics and rubber products
pigments, dyes and carbonless
copy paper
PCBs were “banned” in 1979
[EPA press release - April 19, 1979]
The Environmental Protection Agency today issued final regulations banning
the manufacture of polychlorinated biphenyls (PCBs) and phasing out most
PCB uses. PCBs are toxic and persistent chemicals primarily used as insulating
fluids in heavy-duty electrical equipment in power plants, industries, and large
buildings across the country.
The EPA rules will gradually end many industrial uses of PCBs over the next
five years, but will allow their continued use in existing enclosed electrical
equipment under carefully controlled conditions.
EPA estimates that 150 million pounds of PCBs are dispersed throughout the
environment, including air and water supplies; an additional 290 million pounds
are located in landfills in this country
Spokane
River
Nov. 2002
Lake Michigan
EPA, 2004
N
Concentration
PCBs
µg PCB/Kg sediment
Lake Erie Sediments
PCBs
EPA, 2004
After 25 years, PCBs continue to persist in the Environment
Persistent Organic Pollutants
Poor water solubility
High solubility in Lipids and Organic Solvents
Potentially long half lives
DDT
PCB
Dioxin
Half Life
½ Life
The time it takes for a chemical to degrade
To ½ of its original concentration.
Ci
½ Ci
t1/2
time
½ Life and Organochlorines
PCBs
1 month
2-6 years
> 60 years
Dioxin
1 - 30 years (7 years in humans)
DDT
28 days
15 – 20 years
up to 150 years
Environmental Persistence
Water Column
Solubility of < 0.2 μg/L
Short Half life
Sediments
(longer half-life)
Environmental Persistence,
Half Life and Solubility
An Important Organic Solvent: Octanol
C8H18O
Neutral organic chemicals are soluble in organic solvents
The Octanol-Water Partitioning coefficient
C8H18O
Octanol and water are immiscible
Density: 0.824 g/cm3
octanol
water
C8H18O
Partitioning
Carbon/hydrogen
Octanol (Carbon/Hydrogen)
water
C10H20
Add 10 mg chemical
1 L Octanol
1L Water
separate
chemical
chemical
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
Add 10 mg chemical
1 L Octanol
1L Waterl
separate
chemical
chemical
0.01 mg
L
Water phase
9.99 mg
L
octanol phase
Kow =
9.99 mg
L
0.01 mg
L
= 999
Kow of some Organochlorine Compounds
PCBs
2,000,000
DDT
4,000,000
Dieldrin
158,000
Toxaphene
316,000
Environmental Persistence
Water Column
Solubility of < 0.2 μg/L
Short Half life
Sediments
(Carbon)

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