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| Titel |
Comparing the weight method and the use of the tracer Uranine for assessing pesticide drift on soils |
| VerfasserIn |
G. García-Santos, D. Scheiben, F. Leuenberger, C. R. Binder |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250024559
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| Zusammenfassung |
| Drift from pesticide backpack-spraying is of major importance in the highlands of Colombia,
where more than 20% be drifted by wind effects. This study assesses the usefulness of the
weight method and the use of the tracer Uranine for assessing pesticide drift distribution on
soils. The weight method has been used in developing countries and consists of weighing
previously dried papers, installed close to the soil surface, before and after spraying a known
amount of water. Relative humidity, temperature, direction and speed of the wind were
monitored during the experiments. The tracer Uranine is often used for groundwater studies.
Uranine was added to the water and sprayed by the farmer in the same way he would spray
any pesticide mixture. The same papers used in the previous method were stored after the
spraying and weighing. The tracer was extracted in water and analyzed using a
fluorescent spectrometer. The advantage of Uranine over other tracers is its easy
extraction with water and low detectable concentration. No solvents are required for the
extraction.
The experiments were performed during two months in the wet season in the region of
Vereda la Hoya, Boyaca, Colombia at an altitude of 2800 m a.s.l., from September to
October. Each experiment lasted about 30 min. The fast-changing meteorological conditions
in the region affected the success of the weight method. The paper’s weight was very
sensitive to atmospheric high relative humidity and different evaporative conditions in grass
and bare ground. Location of the blanks was essential and had to represent each
of the different experimental evaporative conditions. Although the method was
easy to implement, we consider that it is not appropriate for areas characterized by
high evapotranspiration rates, and fast-changing climatic conditions as found in the
Colombian highlands above 2800 m a.s.l. Whereas Uranine was not sensitive to
different evapotranspiration rates nor fast changing climatic conditions, this method
is affected by radiation, limiting its explanatory power during sunny days with
high radiation. Remarkably, the drift measured with the weight method was on
average 80% lower than the drift measured with Uranine. Very low values were
only detectable with the tracer method. Therefore, the tracer Uranine is considered
particularly suitable for assessing pesticide drift on soils in the highlands of Colombia. |
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