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Environmental Toxicology and Chemistry

Environmental Toxicology and Chemistry. Department of Environmental and Molecular Toxicology NCSU. Predicting Environmental Fate and Effects II. Irreversible Reactions. Hydrolysis. RX + H 2 O = R OH + H X Neutral, acid and base hydrolysis. Nucleophilic displacement reactions. Photolysis.

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Environmental Toxicology and Chemistry

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  1. Environmental Toxicologyand Chemistry Department of Environmentaland Molecular ToxicologyNCSU

  2. Predicting Environmental Fate and Effects II

  3. Irreversible Reactions

  4. Hydrolysis • RX + H2O = ROH + HX • Neutral, acid and base hydrolysis. • Nucleophilic displacement reactions

  5. Photolysis • Direct and indirect photolysis. • Results in transformations such as isomerization, bond cleavage, intramolecular rearrangement, among others. • Main reaction in atmosphere.

  6. Oxidation-Reduction Reactions • oxidation means a loss of electrons: • oxidizing agents are electrophiles • net effect: either an increase in the oxidation state of that chemical or the incorporation of oxygen into the molecule. • Reduction reactions involve an electron donor known as the reductant and an electron acceptor known as the oxidant.

  7. Biotransformations

  8. Predicting Environmental Transformations

  9. Predicting Equilibria and Rates

  10. Modeling Environmental Fate

  11. Calculated Chemical Distribution in a Hypothetical Pond

  12. Calculated Chemical Distribution in the Environment

  13. Quantitative Structure-Activity Relations (QSAR)

  14. Microcosms

  15. Microcosms

  16. Model Ecosystem

  17. Environmental Fate Models • General steps: • 1- Definition of the spatial and temporal scales and the establishment of the environmental compartments of interest. • 2- Identification and quantification of the source emissions. • 3- Writing of the mathematical expressions for advective and diffusive transport processes. • 4- Quantification of the chemical transformation processes

  18. References • 1-Crosby, D.G. Environmental Toxicology and Chemistry. 2000. Oxford University Press, New York. • 2- Shea, D. Transport and Fate of Toxicants in the Environment. In: Hodgson and Levi (Eds), A Textbook of Modern Toxicology, Second Edition, Appleton and Lange, 1997.

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