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Integrated Field Lysimetry and Porewater Sampling for Evaluation of Chemical Mobility in Soils and Established Vegetation
Published on: July 4, 2014
Adsorption of glyphosate on variable-charge, volcanic ash-derived soils
L Cáceres-Jensen1, J Gan, M Báez
1Dep. de Química de los Materiales, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
Journal of Environmental Quality
|May 26, 2009
Summary
Glyphosate herbicide adsorption in Chilean volcanic soils shows strong binding, especially at lower pH, with hysteresis. Its presence impacts soil phosphorus retention differently across soil types, suggesting varied long-term effects on nutrient availability.
Area of Science:
- Environmental Chemistry
- Soil Science
- Agrochemistry
Background:
- Glyphosate is a widely used, non-selective herbicide crucial in agriculture.
- Its adsorption behavior in variable charge soils, particularly volcanic soils in Chile, is not fully understood.
- Understanding glyphosate-soil interactions is vital for predicting its environmental fate and impact on nutrient cycling.
Purpose of the Study:
- To investigate the adsorption kinetics, equilibrium isotherms, and pH-dependent adsorption of glyphosate in volcanic ash-derived soils.
- To evaluate the influence of glyphosate on soil phosphorus retention.
- To elucidate the mechanisms of glyphosate and phosphate adsorption in Andisols and Ultisols.
Main Methods:
- Selected three volcanic ash-derived soils: Andisols (Nueva Braunau, Diguillin) and Ultisols (Collipulli).
- Conducted adsorption kinetics and equilibrium isotherm studies.
- Assessed the effect of pH on glyphosate adsorption and its impact on phosphate adsorption.
Main Results:
- Glyphosate adsorption was rapid, strong, and non-linear, well-described by the Freundlich model (n(fads) < 0.5), indicating significant hysteresis.
- Adsorption capacity (K(ads)) increased significantly with decreasing pH.
- Glyphosate at high concentrations altered phosphate adsorption, increasing it in Andisols but not in Ultisols, suggesting different binding mechanisms and site occupation.
Conclusions:
- Glyphosate exhibits strong adsorption in Chilean volcanic soils, influenced by pH and soil type.
- Different adsorption mechanisms for glyphosate and phosphate exist, with potential long-term implications for phosphorus availability.
- Volcanic soils' unique properties influence contaminant retention, highlighting risks of pollution with intensive agricultural use.
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