Study of chemical and physical properties and soil sorption of metolachlor and carbofuran in three tropical soils

The sorption of organic compounds to soil is mainly through organic matter components. The organic matter amount and type depends on soil properties such as pH, conductivity, particle size and calcium carbonate content. Therefore, organic pesticide movement-through soil strongly depends on the genesis of organic matter. Organic matter has fractions such as humic acid (HA) and fluvic acid (FA), fats and oils. For this study three tropical soils were chosen, Aguilita, Catano and Tiburones. Some of their organic matter properties, such as total acidity, UV-Vis and IR spectra were related to the sorption coefficient (Koc) of carbofuran and metolachlor. Sorption coefficients in Aguilita, Catano and Tiburones were between 34 and 1,181 ml/g for carbofuran and between 90 and 298 ml/g for metolachlor. Solutions of 100 ug/ml HAs from Aguilita, Catano, and Tiburones dissolved in 0.05N NaHC03 of pH 8.1 had E4/E6 absorption values of 5.5, 4.9 and 3.2, respectively; and those from FA in 2N HCl had values of 10.0, 6.5 and 10.4, respectively. These values suggest a highly aromatic content for HA from Tiburones (E4/E6 ~3) and mainly aliphatic for Aguilita soil. Fulvic acids from Aguilita and Tiburones soils had highly aliphatic character (E4/E6 > 8) whereas that of Catano was intermediate. Data suggest that differences in metolachlor and carbofuran Koc values for the above mentioned soils are mainly due to differences in HA and FA properties of the soils.

Issue Date:
Jul 09 2006
Publication Type:
Conference Paper/ Presentation
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 Record created 2017-04-19, last modified 2019-08-26

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