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Metsulfuron methyl sorption-desorption in field-moist soils
Tomas Berglöf1, William C Koskinen, Michael J Duffy
1Swedish University of Agricultural Sciences, Department of Environmental Assessment, P.O. Box 7050, SE-750 07 Uppsala, Sweden.
Journal of Agricultural and Food Chemistry
|May 29, 2003
Summary
This study introduces a new method using supercritical fluid carbon dioxide to measure pesticide sorption in moist soils. This approach accurately predicts pesticide binding across different soil types and pH levels.
Area of Science:
- Environmental Chemistry
- Soil Science
- Analytical Chemistry
Background:
- Traditional pesticide sorption coefficients (K(d)) are often measured using batch slurry methods, which may not accurately represent field conditions.
- Field-moist or unsaturated soils present unique challenges for accurately determining pesticide sorption due to varying water content and species distribution.
Purpose of the Study:
- To determine the sorption coefficients (K(d)) of metsulfuron methyl, a weak acid pesticide, in field-moist soils.
- To develop a more accurate method for assessing pesticide sorption under realistic soil moisture conditions.
- To investigate the use of supercritical fluid extraction for pesticide sorption analysis.
Main Methods:
- Utilized low-density supercritical fluid carbon dioxide (SF-CO(2)) to selectively extract the molecular species of metsulfuron methyl from soil water.
- Conducted experiments on sandy loam, silt loam, and clay loam soils at 11% water content.
- Calculated sorption coefficients (K(d)) for the neutral metsulfuron methyl species.
Main Results:
- Sorption coefficients (K(d)) for the molecular species of metsulfuron methyl were determined as 120 mL g(-1) for sandy loam, 180 mL g(-1) for silt loam, and 320 mL g(-1) for clay loam at 11% water content.
- Successfully predicted K(d) values obtained from traditional batch slurry methods using the neutral species K(d) values, pK(a) of metsulfuron methyl, and soil pH.
- Demonstrated the efficacy of supercritical fluid extraction in determining sorption coefficients at low water contents.
Conclusions:
- Supercritical fluid extraction offers a viable method for determining pesticide sorption coefficients in field-moist soils.
- The combination of neutral species K(d) values, pesticide pK(a), and soil pH allows for accurate prediction of pesticide sorption across varying soil conditions.
- This approach provides a simplified yet effective means to predict pesticide sorption in soils at different pH levels, improving environmental risk assessments.