Bioavailability Of Metals Associated With Ecotox Endpoints

1. Bioavailability Of Metals Associated With Ecotox Endpoints Dan Benn

2. OUTLINE • Lets talk metals • How are they bad to organisms? • What contributes to their Bioavailability? • How do different environmental conditions contribute to the different chemical states (availability) of metals? • Recap

3. Why metals bad • Not all metals bad • Essentials metals. Too much Bad. Too little Bad. required for enzyme catalysis, molecular transport, protein structure, control osmotic pressure…. • Life stage of exposure Developmental End of life Dormant until puberty or use (stored)

4. Metals Bad Because “…aluminum, antimony, arsenic, cadmium, lead, mercury, and silver cause conditions including hypophosphatemia, heart disease and liver damage, cancer, neurological and cardiovascular disease, central nervous system damage, encephalopathy, and sensory disturbances.” (Maier et. al., 2000).

6. Bioavailability • What is Bioavailability?

8. Bioavailability cont. • Routes of exposure Dermal, Inhalation, Ingestion • Key factors in Bioavailability Metal Chemistry, CEC, Redox Potentials, pH

9. Metal Chemistry • Most metals are Cationic (Positive Charge) • Cations react with negatively charged surfaces of clay minerals, anionic salts (phosphates and sulfates), and negative functional groups (hydroxides and thiols of humic substances, and adversely with negatively charged cell surfaces)

10. Metal Chemisrty cont • Metal cations compete for limited number of cation exchange sites with larger multi-valences replacing smaller monovalent ones • Metals can also be negatively charged, anions • Reasons clay have negatively charged surfaces

14. Cation Exchange Capacity • Reflects a specific soils ability to sorb metals • Clays • Isomorphic substitution • Dissociated edge Si-OH groups • Interlayer sites

15. CEC cont. Soil organic matter (SOM) More area to sorb

18. Redox Potentials Soluble vs insoluble

19. pH • High pH • Low pH • Effects on soils

24. Factors Influencing Bioavailability of Metals. • Biological Factors • Environmental Factors • Anthropogenic Factors

25. Biological effects on Bioavailability • Microbes • Exopolymers • Siderophores • Metallothioneins • Methylation • Redox • Change the pH of microenvironments

26. Environmental • Acidity • Soil Type • Climate

27. Anthropogenic Factors • Acid rain • Mining

28. The End • Thank you

29. Work Cited • Maier, Raina M. et al, Environmental Microbiology, 2000, Academic Press, San Diego, New York, Boston, London, Sydney, Tokyo • Klaassen, Curtis D., Casarett and Doull’s Toxicology: The Basic Science of Poisons, 2001, Medical Publishing Division, New York, Chicago, San Fransico, Lisbon, London, Madrid, Mexico City, Milan, New Delhi, San Juan, Seoul, Singapore, Sydney, Toronto • Sparks, Donald L., Environmental Soil Chemistry, 1995, Academic Press, San diego, New York, Boston, London, Sydney, Tokyo, Toronto • Allen, Herbert E., Bioavailability of Metals in Terrestrial Ecosystems: Importance of Partitioning for Bioavailability to Invertebrates, Microbes, and Plants, 2002, Publication of SETAC • Smith, Lawrence A. et. Al., Remedial Options for Metals-Contaminated Sites, 1995, Lewis Publishers, Boca Raton, New York, London, Tokyo • Hering, Janet G. et. Al., Environmental Chemistry of Trace Metals