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CHARACTERIZATION OF SORPTION AND DEGRADATION OF ORGANIC PESTICIDES APPLIED TO CARBONATIC SOILS

Study investigating sorption and degradation of organic pesticides on carbonatic soils compared to non-carbonatic soils, aiming to characterize properties and understand pesticide behavior.

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CHARACTERIZATION OF SORPTION AND DEGRADATION OF ORGANIC PESTICIDES APPLIED TO CARBONATIC SOILS

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  1. CHARACTERIZATION OF SORPTION AND DEGRADATION OF ORGANIC PESTICIDES APPLIED TO CARBONATIC SOILS Gabriel Nuffield Kasozi Source: usda.gov

  2. Outline • Introduction • Hypothesis • Objective of the study • Materials and Methods • Preliminary results

  3. Introduction • Carbonatic soils are composed of more than 40% Carbonates • Over 500 carbonatic soils in USA and 12 are in South Florida • 85% of Florida vegetables and Tropical fruits grown on Carbonatic soils Source: BMP project report, 2002

  4. Pesticide use • Estimated Annual Total Pesticides Use in SFWMD 14,590 tons . Pesticides Detected in Water Resources in South FL and PR 1Miles and Pfeuffer (1997); 2Potter et al., (2002); 3 Dumas and Rosario (2003); 4Conde-Costas and Rodriguez (1997); FL= Florida; PR = Puerto Rico

  5. Dade Hydrogeologic Cross-section

  6. Introduction • Sorption and degradation determine the fate of an applied organic pesticide Source: SFWMD

  7. Hypothesis • Organic pesticides are adsorbed less on carbonatic soils as compared to non-carbonatic soils • The nature of soil organic matter affects the degree of pesticide sorption • Pesticides degrade faster in Carbonatic soils than in non-carbonatic soils

  8. Objective of the study • Characterize and compare chemical and physical properties of carbonatic soils with those of associated non-carbonatic soils and soils from other areas • Characterize sorption and degradation of selected pesticides and create a database for sorption and transformation of these pesticides on carbonatic soils

  9. Objective of the study • Characterize organic matter (formation, composition and functionality) • Identify the dominant component controlling sorption of pesticides

  10. Materials and Methods • Soils • Soil samples will be taken from South Florida, Puerto Rico and Uganda • Biscayne, Perrine, Pennsuco, Chekika, Krome, Lauderhill, Tamiami • Proposed Pesticides • Atrazine, Ametryne, Oxamyl, Diuron, Endosulfan, Lindane, Carbaryl, Enthroprop, Diazinon

  11. Materials • Experiment 1 • Characterization of soil physical and chemical properties • pH, TOC, CEC, Clay Minerals, CaCO3 • Determination of organic carbon • Walkley-Black method • Thermogravimetry • Sorption isotherms determination (Batch slurry method)

  12. Methods • Experiment 2 • Characterization of organic matter • Stable isotope δ 13C, δ 15N, and C/N ratios • n-Alkanes by GC-FID • Liquid and Solid state 13C and 1H NMR • Pyrolysis GC-MS

  13. Materials and Methods Experiment 3 • Characterization of the nature of binding existing between OM and pesticides • 13C NMR • NanoESI-GC-MS • Flow Calorimetry

  14. Materials and Methods Experiment 4 • Characterization of degradation of pesticides in carbonatic soils • Solvent extractable disappearance of the parent pesticide • Degradation rate coefficients and half-life (t1/2) will be determined

  15. Materials and Methods Data Analysis • Sorption data will be fit using the Freundlich model • Degradation data will be fit using first order kinetics

  16. Preliminary Results Table of results ε= Walkley and Black ; Π = Thermogravimetry

  17. Preliminary Results • Comparison of TG with Walkley-Black for OC determination • Literature Conversion factor: 1.724

  18. Preliminary Results Table of results Soil solution ratio: 1:2

  19. Preliminary Results Linear Sorption Isotherm for Biscayne

  20. Preliminary Results Linear Sorption Isotherm for Krome

  21. Preliminary Results Sorption coefficients of Diuron †(Wauchope et al., 1992, and Nkedi-Kizza et al., 1985)

  22. Preliminary Results Sorption coefficients of Atrazine †(Wauchope et al., 1992, and Nkedi-Kizza et al., 1985)

  23. Advisory Committee:Dr. Peter Nkedi-KizzaDr. Yucong LiDr. David HodellDr. David PowellDr. Willie Harris

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