Exam: Wednesday, April 2

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Exam Wednesday, April 2
Study Guide today
Review Monday, March 31
Student numbers on Exam
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drainage basin 12,000 km2
Dairy and Beef
Sugarcane production contributes two-thirds of
the economic production of Everglades
agriculture, and uses nearly 80 of the crop land
in the EAA
Phosphorus
Sugar, Rice, Veg.
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Eutrophication
Phosphorus
bacteria
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Effectiveness of P controls
Above Target
SWIM target 397 tons
Phosphorus concentrations in the Lake remain at
about 117 ppb
The target level is 40 ppb.
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Internal Loading
Fe3 high oxygen
Fe2 low oxygen
Dissolved phosphorus combines with oxidized iron
(Fe3) to create an insoluble compound that
becomes buried in lake sediments.
Fe3 PO43- Fe(PO4)
solid
If oxygen contents are reduced (anoxic bottom
sediments) the Fe3 converts to Fe2 which
solubilizes the compound returning P to water.
2
3-
(PO4)
Fe
to water
P released by sediments is taken up by
photosynthetic algae faster than it can be
returned to the sediments
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Mercury
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Mercury is naturally occurring
(coal, volcanism, rock weathering)
Anthropogenic sources include

• combustion of coal (1)
• oil product combustion
• cement production
• lead production
• zinc production
• iron and steel production
• mercury production
• gold production.

Enters water bodies principally from the
atmosphere
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Forms of Mercury
The dominant forms of mercury are Hgo and
Hg2 which often occurs as HgCl2 (mercuric
chloride) in many aqueous environments.
Hg2
interacts with soil and sediment particles
becoming part of lake bottom sediments (limits
availability)
Mercury, however, can undergo chemical changes in
lakes which render mercury more environmentally
dangerous
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Mercury as a persistent, bioaccumulative toxin
Bioaccumulation concentration of a chemical in
organisms as it moves up the food chain.
Methylation conversion of inorganic forms of
mercury Hg2 to an organic form methyl
mercury (CH3Hg)
Methylmercury attaches to proteins in animals
(enters food chain)
Methylmercury has a half-life in human blood of
about 50 days.
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Mercury Methylation
Methylation occurs in the absence of oxygen
(anoxic or anaerobic conditions) but in the
presence of organic carbon and sulfate (SO42-)
Occurs primarily in bottom sediments as a
byproduct of the life processes of
sulfate-reducing bacteria (SO4 to H2S) that live
in high sulfur, low oxygen environments.
Carbon loses electrons (oxidized), oxygen
gains electrons (reduced). Oxygen is the electron
acceptor.
-2
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microbes
SO4-2 H2S
Sulfur is the electron acceptor.
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The exact role of sulfate-reducing bacteria In
mercury methylation is poorly understood
However, bacterial sulfate reduction requires
sulfate. The addition of sulfate to water
stimulates the metabolic activity of
sulfate-reducing bacteria and the inadvertent
methylation of inorganic mercury
Sulfate concentrations in EAA runoff and Lake
Okeechobee average more than 50 times background
concentrations in the pristine Everglades
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Hg2 from coal, volcanism, rock weathering
Water
Sediments
(Bound)
Sulfur reducing bacteria, low O2
methylmercury
Food Chain
bioaccumulation
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Bioaccumulation Factors
Concentration in organism Concentration in water
BAF
Methylmercury is rapidly taken up but only slowly eliminated from the body by fish and other aquatic organisms, so each step up in the food chain (bio)magnifies the concentration from the step below.Bioaccumulation factors (BAF's) of up to 10 million in largemouth bass have been reported for the Everglades.Fish-eating birds, otters, alligators, raccoons and panthers can have even higher bioaccumulation factors. Methylmercury in the organs and tissues causes birth defects disorders of the brain, reproductive system, immune system, kidney, and liver at extremely low levels in food.                                      
   
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Sidebar Fluorescent Lights
A typical fluorescent lamp is composed of a
phosphor-coated glass tube with electrodes
located at either end. The tube contains
mercury, of which only a very small amount is in
vapor form. When a voltage is applied, the
electrodes energize the mercury vapor, causing
it to emit ultraviolet (UV) energy. The phosphor
coating absorbs the UV energy, causing the
phosphor to fluoresce and emit visible light.
Each year, an estimated 600 million fluorescent
lamps are disposed of in US landfills amounting
to 30,000 pounds of mercury waste.
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Other Bioaccumulative Toxins
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Synthetic Organic Chemicals
Organochlorines
Dioxins Pesticides
Chlordane
Dioxin
PCBs
Organic Solvents Cleaning agents
DDT
PCB
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Why do they bioaccumulate?
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Solubility
Organochlorines as well as many other
synthetic organic compounds are poorly soluble in
water
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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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Ionic Compounds
NaCl Na Cl-
Na
Sodium Chloride 350 g/L Potassium Chloride 280
g/L
Why?
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Liquid water - Vibration and rotation
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NaCl Na Cl-
Na
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Dioxin
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PCBs
Water Solubility
Aroclor 1221 (21 Chlorination) 500-1500 ppb
Aroclor 1230 (30 Chlorination) 85-92
ppb Aroclor 1240 (40 Chlorination) 40-170 ppb
Aroclor 1254 (54 Chlorination) 10-31
ppb Aroclor 1260 (60 Chlorination) lt1 ppb
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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 is inversely
proportional to its solubility in water.
Lipid (Carbon/hydrogen)
Carbon/hydrogen
water
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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
Banned in 1979
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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Mirex
highest levels ever recorded in a living
organism.