Use of organosmectites to reduce leaching losses of acidic herbicides
The modification of smectitic clays with organic cations via cation-exchange reactions produces sorbents with an increased sorption capacity for organic compounds such as acidic herbicides. These organoclays (OCIs) could be used as carriers in controlled release formulations of herbicides to decrease their contamination potential. Various OCIs and two acidic herbicides (bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4 (3H) one 2,2-dioxide] and dicamba [2-methoxy-3,6-dichlorobenzoic acid]) were selected and herbicide-OCI complexes were prepared by either sorbing the herbicides on the OCI from solution or by dry mixing of both components. Those preparations were assayed as controlled-release formulations under static (water solution) and dynamic (soil column leaching) conditions. Herbicide release in closed (static) systems was fast and reached a maximum concentration after 10 to 20 h. The total herbicide released ranged from 20 to 100% of the active ingredient initially incorporated in the complex depending on the sorption capacity of the OCI for the herbicide and the strength of herbicide-OCI interaction (aging time). Complexes releasing <50% of the herbicide, corresponding to the most sorptive OCIs, may not be appropriated for weed control. Total leaching losses in soil columns were reduced from 94% for free technical bentazone to 55 to 90% for bentazone-OCI complexes, and from 100% for technical dicamba to 50 to 100% for dicamba-OCI complexes. Maximum concentrations in the leaching profiles of the herbicide-OCI complexes were much smaller than for the technical compounds. Bioassays of dicamba-OCI complexes as preemergence herbicide showed the same efficiency as the technical compound. These results suggest OCIs as possible carriers in controlled release formulations for very mobile and persistent acidic herbicides, thereby decreasing their potential for surface and ground water contamination.
| Main Authors: | , , , |
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| Other Authors: | |
| Format: | artículo biblioteca |
| Language: | English |
| Published: |
Soil Science Society of America
2003
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| Online Access: | http://hdl.handle.net/10261/61463 http://dx.doi.org/10.13039/501100007273 http://dx.doi.org/10.13039/501100011011 |
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| Summary: | The modification of smectitic clays with organic cations via cation-exchange reactions produces sorbents with an increased sorption capacity for organic compounds such as acidic herbicides. These organoclays (OCIs) could be used as carriers in controlled release formulations of herbicides to decrease their contamination potential. Various OCIs and two acidic herbicides (bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4 (3H) one 2,2-dioxide] and dicamba [2-methoxy-3,6-dichlorobenzoic acid]) were selected and herbicide-OCI complexes were prepared by either sorbing the herbicides on the OCI from solution or by dry mixing of both components. Those preparations were assayed as controlled-release formulations under static (water solution) and dynamic (soil column leaching) conditions. Herbicide release in closed (static) systems was fast and reached a maximum concentration after 10 to 20 h. The total herbicide released ranged from 20 to 100% of the active ingredient initially incorporated in the complex depending on the sorption capacity of the OCI for the herbicide and the strength of herbicide-OCI interaction (aging time). Complexes releasing <50% of the herbicide, corresponding to the most sorptive OCIs, may not be appropriated for weed control. Total leaching losses in soil columns were reduced from 94% for free technical bentazone to 55 to 90% for bentazone-OCI complexes, and from 100% for technical dicamba to 50 to 100% for dicamba-OCI complexes. Maximum concentrations in the leaching profiles of the herbicide-OCI complexes were much smaller than for the technical compounds. Bioassays of dicamba-OCI complexes as preemergence herbicide showed the same efficiency as the technical compound. These results suggest OCIs as possible carriers in controlled release formulations for very mobile and persistent acidic herbicides, thereby decreasing their potential for surface and ground water contamination. |
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