1. Exam: Wednesday, April 2 Study Guide: today Review: Monday, March 31 Student numbers on Exam

2. Dairy and Beef Sugar, Rice, Veg. drainage basin 12,000 km 2 Sugarcane production contributes two- thirds of the economic production of Everglades agriculture, and uses nearly 80% of the crop land in the EAA Phosphorus

3. Eutrophication Phosphorus Photosynthetic life bacteria O2O2

4. SWIM target: 397 tons Phosphorus concentrations in the Lake remain at about 117 ppb The target level is 40 ppb. Effectiveness of P controls Above Target

5. Internal Loading Dissolved phosphorus combines with oxidized iron (Fe 3+ ) to create an insoluble compound that becomes buried in lake sediments. If oxygen contents are reduced (anoxic bottom sediments) the Fe 3+ converts to Fe 2+ which solubilizes the compound returning P to water. P released by sediments is taken up by photosynthetic algae faster than it can be returned to the sediments Fe 3+ + PO 4 3- = Fe(PO 4 ) solid (PO 4 )Fe to water 2+ Fe 3+ high oxygen Fe 2+ low oxygen 3-

6. Mercury

7. Mercury is naturally occurring 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 (coal, volcanism, rock weathering)

8. Forms of Mercury The dominant forms of mercury are Hg o and Hg 2+ which often occurs as HgCl 2 (mercuric chloride) in many aqueous environments. Mercury, however, can undergo chemical changes in lakes which render mercury more environmentally dangerous Hg 2+ interacts with soil and sediment particles becoming part of lake bottom sediments (limits availability)

9. Mercury as a persistent, bioaccumulative toxin Methylation: conversion of inorganic forms of mercury Hg 2+ to an organic form: methyl mercury (CH 3 Hg+) Methylmercury has a half-life in human blood of about 50 days. Methylmercury attaches to proteins in animals (enters food chain) Bioaccumulation: concentration of a chemical in organisms as it moves up the food chain.

10. Methylation occurs in the absence of oxygen (anoxic or anaerobic conditions) but in the presence of organic carbon and sulfate (SO 4 2- ) Occurs primarily in bottom sediments as a byproduct of the life processes of sulfate-reducing bacteria (SO 4 to H 2 S) that live in high sulfur, low oxygen environments. Mercury Methylation SO 4 -2 H 2 S microbes O 2 + Carbon (C) CO 2 0 0 +4 -2 x 2 = -4 +6 -2 Carbon loses electrons (oxidized), oxygen gains electrons (reduced). Oxygen is the electron acceptor. Sulfur is the electron acceptor.

11. 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 The exact role of sulfate-reducing bacteria In mercury methylation is poorly understood

12. Hg 2+ from coal, volcanism, rock weathering Water Sediments (Bound) Sulfur reducing bacteria, low O 2 methylmercury Food Chain bioaccumulation

13. 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. Bioaccumulation Factors Concentration in organism Concentration in water BAF =

14. 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.

15. Other Bioaccumulative Toxins

16. Synthetic Organic Chemicals Dioxins Pesticides PCBs Organic Solvents Cleaning agents Chlordane Dioxin PCB DDT Organochlorines

17. Why do they bioaccumulate?

18. Solubility Organochlorines as well as many other synthetic organic compounds are poorly soluble in water

19. Dioxin PCB DDT insoluble 10-31 µg/L (50% Cl ) 0.2 µg/L Principally carbon, hydrogen

20. Sodium Chloride350 g/L Potassium Chloride280 g/L Ionic Compounds Why? NaClNa + + Cl - Na +

21. Liquid water - Vibration and rotation

22. NaClNa + + Cl - Na +

23. Dioxin

24. 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) <1 ppb PCBs Water Solubility

25. Organic Solvents Improving Solubility Hexane Structural similarity between the chemical and the solvent. Soap/detergents

26. Structural similarity between the chemical and the solvent. Lipids and Solubility

27. Solubility A chemical’s solubility in lipids is inversely proportional to its solubility in water. Carbon/hydrogen Lipid (Carbon/hydrogen) water

28. Bio-Accumulation Water and phytoplankton to zooplankton: 800 x Zooplankton to fish: 31 x Overall: 120,000 times original concentration Fish to eagle: 4.8x

29. Smallmouth bass - 1100-1800 ppb Round gobies - 200-800 ppb Zebra mussels - 100 ppb Spokane River Nov. 2002 PCBs Banned in 1979

30. Seawater Arctic cod muscle Narwhal blubber 14 - 46 ppb 0.0003 ppb 2440 - 9160 ppb Toxaphene Biomagnification

31. Mirex highest levels ever recorded in a living organism.