Study of Chemical and Physical Properties and the Soil Sorption of Metolachlor and Carbofuran in Three Tropical Soils

Study of Chemical and Physical Properties and the Soil Sorption of Metolachlor and Carbofuran in Three Tropical Soils Jos é A. Dumas, Peter Nkedi-Kizza and Rafael Montalvo-Zapata

[object Object],[object Object],Introduction Organic Matter Clay Two main soil components associated to pesticide sorption are clay and organic matter

[object Object],Organic matter Organic Matter – Humic and fulvic acids

Humic acid-pesticide interaction Van der Waals and electrostatic interactions. How pesticide’s sorption occurs?

Objectives ,[object Object],[object Object]

Hydrogeographic (HP) map of Puerto Rico North Coastal Limestone Aquifer South Coastal Alluvial Aquifer Chemico-pharmaceutical industries High urban development

Sampling areas and Soil Series Selected Tiburones Catano Aguilita

Methods ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Soil properties CCE-Calcium carbonate equivalen; WHC-Water holding capacityt Soil Series pH CCE % Clay % Silt % Sand % WHC Aguilita 8.18 63.13 47.68 22.88 29.44 45 Cata ñ o 8.60 14.01 4.56 3.36 92.08 22 Tiburones 4.07 0.84 17.44 2.84 79.72 38

Organic matter properties HA-humic acid; FA-fulvic acid; 1 mg/50g soil; OC-organic carbon Soil Series HA mg 1 FA mg 1 HA/FA OC % Fat mg/kg OC Aguilita 600 590 1.0 4.08 950 Cata ñ o 25 84 0.3 0.53 161 Tiburones 990 490 2.0 7.93 2730

Fulvic and Humic acid properties E4/E6-absorbance ratio at 400 and 600 nm Soil Series E4/E6 Total Acidity (meq/g humic) HA FA HA FA Aguilita 5.5 10.0 1.4 2.8 Cata ñ o 4.9 6.5 ND 0.44 Tiburones 3.2 10.4 1.6 3.2

Potentiometric tiltration of Fulvic acid -COOH Phenolic OH

Potentiometric tiltration of Humic acid Non clearly defined acidic group protons

Derivative spectrum of Humic acid (100ug/mL) Aguilita Catano Tiburones

Derivative spectrum of Fulvic acid (100ug/mL) Aguilita Catano Tiburones

Main functional groups of Fulvic acids ( β -humus) identified by ATR-IR Aguiliita Catano Tiburones Benzene rings Hydroxy groups Aromatic C-H Si-H C=O C-O

Main functional groups of Humic acids identified by ATR-IR Aguiliita Catano Tiburones

Structure of pesticides Metolachlor Carbofuran Chloroacetanilide Carbamate

Chemical and physical properties of Metolachlor and Carbofuran MET-metolachlor; CAR-carbofuran Name Family Sol. (mg/L) Koc (mL/g) Kow pK b MET cloroacetanilide 530 200 2820 NA CAR carbamate 700 14-160 17-26 NA

Sorption isotherms for Metolachlor

Soil sorption coefficient Soil Series Metolachlor Kd Aguilita 3.6 Cata ñ o 1.2 Tiburones 9.3

Conclusion ,[object Object],[object Object]

[object Object],Acknowledgement

Study of Chemical and Physical Properties and the Soil Sorption of Metolachlor and Carbofuran in Three Tropical Soils

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Study of Chemical and Physical Properties and the Soil Sorption of Metolachlor and Carbofuran in Three Tropical Soils