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Kinetic Models Considered Jeremy Dyson Basel, Switzerland

Kinetic Models Considered Jeremy Dyson Basel, Switzerland. Introduction. Selected core models for parent compounds & metabolites in soil and water-sediment studies Models can be applied to other studies, e.g. hydrolysis

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Kinetic Models Considered Jeremy Dyson Basel, Switzerland

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  1. Kinetic Models ConsideredJeremy DysonBasel, Switzerland

  2. Introduction Selected core models for parent compounds & metabolites in soil and water-sediment studies Models can be applied to other studies, e.g. hydrolysis Models chosen as simple & sensible approaches to representing behaviour from pseudo-mechanistic to more pragmatic perspectives Models displayed in terms of: • Integrated equations based on initial conditions • Differential of above for solving new problems • Differential equations without initial conditions • Endpoint calculation (DT50/DT90) from parameters

  3. Outline The Core Models • Single First Order • Biphasic Models • Gustafson & Holden • Bi-Exponential • Hockey Stick • Lag Phase Models • Modified Hockey Stick • Logistic Alternatives & Links to Leaching Models Conclusion

  4. Single First Order (SFO) Fixed Shape DT90 = 3.32 x DT50 Assumes microbes not limiting Degradation  % Remaining

  5. Single First Order (SFO)

  6. Biphasic Models Generally: DT50s Shorter DT90s Longer DT50 DT90

  7. Biphasic Models Some Causes of Biphasic Behaviour • Aged sorption • Non-linear sorption • Declining microbial activity • Spatial variations in field • Seasonal changes in weather

  8. Gustafson & Holden (FOMC)

  9. Bi-Exponential (DFOP or FOTC)

  10. Hockey Stick (HS)

  11. Lag Phase Models Lag Phase

  12. Modified Hockey Stick

  13. Logistic

  14. Alternatives & Links to Leaching Models Alternatives models can be used, but: • Needs to be justified, e.g. Michaelis-Menten kinetics • Need to avoid, where possible: • Time-dependent endpoints • Concentration-dependent endpoints • Large number of parameters • Microbial population dynamics • Avoid Timme et al. as already noted in Guideance Identify biphasic kinetics for use in leaching models • Not possible, but can link to DFOP for estimation

  15. Alternatives & Links to Leaching Models

  16. Conclusion Core models able to handle most kinetics problems Hence focus on solving problems using these models

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