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Primary and secondary pesticide drift under sub-humid climate; field measurements and modeling approaches

Ohad Zivan, Yael Dubowski

Using a novel laboratory apparatus in which both condensed and gaseous phases are monitored simultaneously, we determined the kinetics and quantum yield of photo-oxidized sorbed pesticides as well as identified their volatile and non-volatile products. This information enabled us to better estimate the fate of pesticides that remain at the surface-air interface during the dry months that followed their application. After completing the chemical analysis of the samples collected in September 2014, most of Year 5 was dedicated to analysis of the results from all of our spraying campaigns at the Matitiyahu research station (total of 9 spraying events). The obtained vertical profiles of airborne pesticides concentrations were analyzed as a function of the meteorological conditions and the pesticide vapor pressure. Fluxes of pesticide drift during and after application were calculated, in order to obtain a more general understanding of the drift problem. In addition, an effort has been done to estimate to what extent the inner areas of the orchard contribute to the drift. An integrated volume PUFF model was written (in Matlab) to simulate these experiments. The model was developed both numerically and analytically. A manuscript summarizing our field measurements and the CALPUFF modeling regarding atmospheric transport of pesticide at the Hula Valley has been submitted to Atmospheric Environment and is currently under review. A second manuscript discussing the Matityahu orchard experiments is under preparation.