Choice of Activable Tracer for Spraying Agricultural Insecticides by Helicopter

概要

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The fundamental studies were made on the selection of activable tracers which were usable to examine the distribution of agricultural insecticide sprayed by helicopter. Considering the conditions that the samples are organic substances, sufficiently strong radioactivity should be produced in a short irradiation-time, and the half life of the activity is desired to be longer than two hours for the sake of convenience of activity measurement, manganese, gold and europium were selected as typical tracers. Other conditions required for the field experiments were checked on these elements. Minimum detectable limits of each tracer was estimated from both the activity produced by each tracer and the background due to interference components in the sample. As a result, europium tracer was found to be the best in sensitivity (minimum detectable limit was 1.5×10-10gEu/5cm2filter paper) and also in cost, if the sampling was carried out using filter paper and a thin scintillator was used to measure low energy photons. After all, it was concluded that europium would be the most suitable tracer for the determination of distribution of insecticide sprayed by helicopter.
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