PESTICIDE STORAGE AND RELEASE IN UNSATURATED SOIL IN ILLINOIS, USA
The chemical fate and movement of pesticides may be subject to transient storage in unsaturated soils during periods of light rainfall, and subsequent release into shallow groundwater by increased rainfall. The objective of this study was to conduct field-scale experiments to determine the relative...
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| Published in: | Journal of environmental science and health. Part B, Pesticides, food contaminants, and agricultural wastes Vol. 36; no. 3; pp. 245 - 260 |
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| Main Authors: | , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Philadelphia, PA
Taylor & Francis Group
01-01-2001
Taylor & Francis |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | The chemical fate and movement of pesticides may be subject to transient storage in unsaturated soils during periods of light rainfall, and subsequent release into shallow groundwater by increased rainfall. The objective of this study was to conduct field-scale experiments to determine the relative importance of transient storage and subsequent release of agrichemicals from the vadose zone into potential aquifers. Two field-scale experiments were conducted under a rain exclusion shelter. In the 1
×
experiment, atrazine and chlorpyrifos were applied at application-rate equivalents (1.6 kg ha
−1
and 1.3 kg ha
−1
, respectively). In the 4
×
experiment, atrazine was applied in an amount that was four times greater than that usually applied to fields (6.7 kg ha
−1
). Water was either applied to simulate rain or withheld to simulate dry periods. In the 1
×
experiment, atrazine was detected in the water samples whereas chlorpyrifos was not detected in the majority of the samples. The dry period imposed on the treatment plot did not appear to result in storage of the chemicals, whereas the wet period resulted in greater leaching of atrazine, although the concentrations remained less than the Maximum Contaminant Level of 3 μg L
−1
. Both chemicals were detected in soil samples collected from a 20- to 30-cm depth, but it appeared that both chemicals dissipated before the field experiment was concluded. It appeared that the one-time application of atrazine and chlorpyrifos at the label rates did not result in a sufficient mass to be stored and flushed in significant concentrations to the saturated zone. When atrazine was applied at 4
×
and a longer drought period was imposed on the treatment plot, the resulting concentrations of dissolved atrazine were still less than 3 μg L
−1
. Atrazine was detected in only the near-surface (0 to 15 cm) soil samples and the herbicide dissipated before the onset of the dry period in the treatment plot. The results of this field study demonstrated that atrazine and chlorpyrifos were not sufficiently persistent to be stored and then released in significantly large concentrations to the saturated zone. The dissipation half-life of atrazine in the 4
×
application was about 44 days. This study, in addition to others, suggested that atrazine may be less persistent in surface soil than has been generally reported.
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Publication authorized by the Chief of the Illinois State Geological Survey. |
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| Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
| ISSN: | 0360-1234 1532-4109 |
| DOI: | 10.1081/PFC-100103567 |