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Toxic Bioaccumulative Chemicals. Mercury. Most mercury enters aquatic environments from the atmosphere. The dominant inorganic forms are Hg o and Hg 2+ . Positively charged Hg 2 + can become attached to negatively charged organic and inorganic particles in soils and sediments

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Presentation Transcript
slide2

Mercury

Most mercury enters aquatic environments from the atmosphere

The dominant inorganic forms are Hgo and Hg2+.

Positively charged Hg2+ can become attached to negatively

charged organic and inorganic particles in soils and sediments

which tends to immobilize them.

Under anaerobic conditions, Hg2+ can be converted to organic

Methylmercury which is more toxic and persistent in organisms.

Mercury methylation is related to the metabolism of

Sulfur-reducing bacterial under anaerobic conditions

The exact biochemical mechanism is poorly understood.

High sulfur concentrations increase mercury methylation

slide3

The following are required for mercury methylation

Inorganic Mercury

Anaerobic Conditions

Carbon Source (sediments)

Sulfate/Sulfate-Reducing Bacteria

Methylmercury is more directly toxic and remains in

The tissues of organisms longer than inorganic Hg2+.

This allows methymercury to bioaccumulate in organisms

Bioaccumulation occurs when an organism absorbs

a toxic substance at a rate greater than that at which

the substance is lost from the body.

Bioaccumulation allows for biomagnification which

is the increase in concentration of a chemical

in organisms higher up in the food chain.

slide4

Biomagnification: concentration of a chemical in

organisms as it moves up the food chain.

Organisms near the top of the food chain may have concentrations

of mercury millions of times greater than in the aquatic environment

slide5

Other Bioaccumulative Toxins

Synthetic Organic Chemicals

slide6

Synthetic Organic Chemicals

Organic = carbon-rich compounds

Dioxin

Dioxins

Pesticides

PBDE

PCBs

Flame Retardants

PCB

DDT

Organochlorines

slide7

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

slide8

Chemicals like dioxin are acutely toxic

In high doses, but they also can bioaccumulate

creating chronic toxicity at lower doses

The cause of their ability to bioaccumulate

is related to their water solubility.

slide9

Water Solubility

NaCl Na+ + Cl-

Sodium Chloride 350 g/L

Potassium Chloride 280 g/L

Why?

slide10

Water Molecules are Polar

+

+

Unequal distribution of electrons

Oxygen is electron-greedy

-

slide11

NaCl Na+ + Cl-

Cl-

Na+

Sodium Chloride water solubility: 350 g/L

slide13

Organic Chemicals

Carbon-rich compounds

Greases, Oils, Paints, Pesticides, Industrial Chemicals

Grease and Oil

Oil Paint

C16H14OS

Composed mostly of carbon and hydrogen,

and possessing no electrical charge.

slide14

Dioxin

C11H18O2Cl4

DDT

C14H22Cl5

C12H21Cl2

PCB

Principally carbon, hydrogen

Do not possess an electrical charge

slide15

Dioxin

Dioxin water solubility: 0.2 µg/L

slide16

0.2 µg/L

Dioxin

DDT

< 0.1 µg/L

PCB

10 µg/L

Uncharged and principally carbon, hydrogen

slide17

Toxaphene: 3 mg/L

Dieldrin: 186 ug/L

Chlordane: 9 ug/L

slide18

Greases, Oils, Paints, Pesticides, Industrial Chemicals

These types of chemicals are poorly soluble in water

In what substances do they dissolve?

slide19

Hexane

Common Organic Solvents

Carbon-based

D-limonene oil

petroleum

slide20

Organic Solvents

carbon

Hexane

carbon

Acetone

Dioxin

Lipids

carbon

carbon

Carbon-based compounds

dissolve more easily in carbon-

based solvents.

water

slide21
Soap

SO4-

SO4-

SO4-

-SO4

SO4-

SO4-

SO4-

SO4-

SO4-

hydrophobic

hydrophilic

High Carbon Concentration

slide23

Bioaccumulation in Organisms

Lipid Tissue in Organisms

carbon

Fundamental similarity between

the chemical and the solvent.

The chemical essentially dissolves into the lipid tissues

slide24

Synthetic organic chemicals are poorly soluble in water

They are soluble in organic solvents and lipids

Lipids are found in all organisms

Despite low levels of organic chemicals in water due

to their low water solubility, high amounts can

accumulate in the tissues of living organisms

slide25

Water Concentration = 0.2μg/L

Zooplankton concentration = 160 μg/L

Magnification of 800 x

slide26

Zooplankton to fish: 31 x

Fish to eagle: 4.8x

Bio-Magnification

Water and phytoplankton to zooplankton: 800 x

Overall: 120,000 times original concentration in water

slide28

PCBs

Used as insulating fluids and coolants in electrical equipment and machinery from 1929-1977.

Electrical equipment

plasticizers inpaints,

plastics and rubber products

pigments, dyes andcarbonless

copy paper

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

some PCBs act like hormones,

and other PCBs are nerve poisons

PCBs were “banned” in 1979

slide29

Killer Whales

(1000 ppm)

PCBs in Marine Mammals

High on food chain

Lipid tissues

Hazardous

Waste level

(Canada)

slide30

Toxaphene

(670 chemicals)

lipid

carbon

400,000 tons: 1946 to 1974

Seawater

0.0003 ppb

Arctic cod muscle

14 - 46 ppb

50,000 X

Narwhal

blubber

2440 - 9160 ppb

~ 8 M X

slide31

Toxaphene and Mirex: 1959 - 1976

highest levels ever recorded in a living organism.

slide32

Summary

  • Many synthetic organic chemicals are uncharged.
  • 2. Because they are uncharged, they do not permit
  • orientation of water molecules and are poorly soluble
  • in water.
  • 3. Ionic compounds (e.g. NaCl) are about 1 billion times
  • more water-soluble than uncharged organics.
  • 4. Uncharged organic chemicals, however, tend to be
  • soluble in organic solvents and organic materials
  • because of similar carbon-based chemistry.
  • 5. These materials can include lipid tissues in organisms
  • which can lead to biomagnification
slide33

Solubility

carbon

Hexane

carbon

Acetone

Dioxin

Lipids

carbon

carbon

Carbon-based compounds

dissolve more easily in carbon-

based solvents.

water

slide34

Many synthetic organic chemicals, particularly

those like PCBs and DDT are very persistent

in the environment. They last for decades.

They become stored in organic materials

that naturally occur in aquatic and terrestrial systems

Where in these environments

do we find high levels of carbon?

organic matter
Organic Matter

Carbon

Hydrogen

Oxygen

Coiled and convoluted chains of carbon, hydrogen, and oxygen

organic matter1
Organic Matter

H

C

H

C

H

H

H

C

carboxylic

COOH

H

H

C

H

enolic

OH

C

H

H

C

H

H

C

H

C

C

C

C

C

C

C

C

Carbon

Hydrogen

Oxygen

partitioning distribution
Partitioning/Distribution

Organic matter

Soil Solution

Absorption

slide38

Partitioning of neutral organic chemicals into soil

organic matter limits their mobility in the environment

slide40

Solubility of < 0.1 μg/L

Environmental Persistence

Water

DDT

Organic Sediments

Organic chemicals become stored in organic sediments

This protects them from degradation and increases their lifetime in the environment

slide41

N

Concentration

Organic Carbon

mg Carbon /g sediment

Lake Michigan

PCBs

“banned” in 1979

EPA 2004

PCBs

µg PCB/Kg sediment

(parts per billion)

Open water PCB concentration = < 1 part per trillion

slide42

Lake Erie PCB levels

PCBs

EPA, 2004

After 30 years, PCBs continue to persist in the Environment

slide45

DDT

dichloro-diphenyl-trichloroethane

First Modern Pesticide

Insecticide developed to combat insect-borne disease

Use was later expanded to include agriculture

slide46

Rita Island, Okeechobee

Organic soils

DDT levels ranging from

2,200 to 110,000 µg/kg (ppb)

in organic soils and sediments.

slide47

Lake Apopka

30,800 acres

mean depth is 5.4 feet

15 miles northwest of Orlando

Historically characterized by clear water and a highly prized sports fishery, it served as a popular destination for boaters, swimmers, and fishermen for decades.

slide48

In the 1970s, scientists considered Lake Apopka

a prime place to harvest eggs and hatchlings to study

them in captivity.

In 1980 and 1981, scientists counted populations of

1,200 to 2,000 alligators in a single night on the lake

By the late 1980s, they counted only 150 per night

slide49

Pesticide Use in Agricultural Area

Agriculture

Pesticide use included high amounts of DDT

slide50

"Lake Apopka is a big chemical soup,"

Michael Fry, a researcher from the University of California

Tower Chemical Company

TOC content ranges from 33 to 37%

Produced dicofol, a mixture of the pesticide DDT and DDE,

a by-product of DDT. Periodic spills occurred there, but a particularly

large accident in 1980 caused dicofol to spread into the lake

slide51

Alligator Population crash was linked to poor egg viability

DDE, a breakdown product of DDT, is

a major contaminant in Lake Apopka

DDEis known to block the action of testosterone

Apopka's juvenile alligators have abnormal

testes and ovaries and abnormal hormone balances

Estradiol Testosterone

Apopka males had high levels of estradiol relative to testosterone

slide52

' Teeny Weenies '

Alligators in Florida's Lake Apopka have Smaller Penises

Kyla Dunne for PBS June, 1998

http://www.mindfully.org/Pesticide/Alligators-Apopka-PBS2jun98.htm

slide54

Solubility

carbon

Hexane

carbon

Acetone

Dioxin

Lipids

carbon

carbon

Carbon-based compounds

dissolve more easily in carbon-

based solvents.

water

slide55

What is the most common way we daily

dissolve organic substances/chemicals?

slide56
Soap

SO4-

SO4-

SO4-

-SO4

SO4-

SO4-

SO4-

SO4-

SO4-

hydrophobic

hydrophilic

High Carbon Concentration

slide57
Soap

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

Soap micelle

Oil drop in water

slide59

An Important Organic Solvent: Octanol

C8H18O

c

c

c

c

c

c

c

c

Neutral organic chemicals are soluble in organic solvents

slide60

Octanol-Water Partitioning

C8H18O

Octanol and water are immiscible

Octanol Density: 0.824 g/cm3

C8H18O

octanol

water

slide61

Partitioning Between Octanol and Water

Carbon/hydrogen

Octanol (Carbon/Hydrogen)

water

C10H20

slide62

Octanol-Water Partitioning Coefficient

Concentration of chemical in octanol

Concentration of chemical in water

Kow =

At equilibrium

slide63

separate

chemical

chemical

Add 10 mg chemical

1 L Octanol

1L Water

octanol

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

slide64

separate

chemical

chemical

Add 10 mg chemical

1 L Octanol

1L Waterl

9.99 mg

L

9.99 mg

L

0.01 mg

L

Kow =

= 999

0.01 mg

L

octanol phase

Water phase

slide65

Kow of some Organochlorine Compounds

DDT 4,000,000

PCBs2,000,000

Dioxin 6,000,000

chemical in octanol

chemical in water

A high Kow indicates strong interaction

with organic solvents and lipid tissues

slide66

PCBs

Kow = 2,000,000

Used as insulating fluids and coolants in electrical equipment and machinery from 1929-1977.

Electrical equipment

plasticizers inpaints,

plastics and rubber products

pigments, dyes andcarbonless

copy paper

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

some PCBs act like hormones,

and other PCBs are nerve poisons

PCBs were “banned” in 1979

slide67

DDT

Kow = 4,000,000

first modern pesticide (Nobel Prize, 1948)

used with to combat mosquitoes spreading malaria (mosquitoes),

and typhus (lice)

Insoluble in water. Soluble in

most organic solvents, fat, and oils.

Banned in 1972 (U.S.)

slide68

Launch of the

Environmental Movement

Thinning egg shells

Lower hatching rates

Declining Eagle population

Carcinogenic

decline in the eagle population occurred before the DDT years

(bounties between 1917 and 1942)

primates were fed 33,000 times more DDT than the estimated exposure

human volunteers ingested 35 mg of DDT

1962

http://faculty.unionky.edu/rbotkin/RECM_480_ISSUE_16A_YES_BLUE.PPT#291,22,Issue%2016:%20Yes

slide69

Water Filters

Simple Filtration

Ion Removal

Carbon

(most common component)

activated carbon
Activated Carbon

Activation by heating

Extremely porous with high surface area: 500 m2/g

Large surface area = high contact with contaminants

activated carbon1
Activated Carbon

Absorption: spontaneous movement of primarily

organic contaminants from water to

carbon matrix.

Pesticides and other organics essentially dissolve in the carbon

Chlorine sticks to the extensive surfaces

slide72

Ethylbenzene

Monochlorobenzene

MTBE

O-Dichlorobenzene

P-Dichlorobenzene

Styrene

Tetrachloroethene

Toluene

Trichloroethene

VOCs

Antidepressants

Steroids/Hormones

Prednisone, Prednisolone,

Progesterone, Testosterone,

Cortisol/Hydrocortisone

Antibiotics

Ciprooxacin, Trimethroprin,

Sulfamethoxazole

Anxiolytics

Meprobamate

Carbon Filter Removal

2,4-D

2.4.5-TP (Silvex)

Alachlor

Atrazine

Carbofuran

Chlordane

Endrin

Heptachlor Epoxide

Lindane

Methoxychlor

Simazine

Toxaphene

Benzene

Carbon Tetrachloride

Chlorobenzene

Does not remove bacteria or most metals