Field experiment to assess pesticide post-application transfers to the atmosphere. About determining volatilization fluxes

Abstract

The consideration of pesticides in atmosphere is recent in France. And it doesn't exist surveillance program of atmospheric contamination by pesticide products as it exists for other industrial pollutants (ozone, NOx...). Indeed it is not of quantifying a unique pollutant but more than 500 different active materials in about 7000 commercial formulations. It is imaginary to believe that the next years will see being born a universal method allowing to measure all the susceptible pesticides to be present in the atmosphere. We turn more credibly to the development of mathematical models for the estimation of fluxes transfers of pesticides towards the air compartment from the treated surfaces. These last ones coupled with distribution and deposit models will allow to estimate contamination levels according to removal from sources. Three different phenomena are at the origin of the presence of pesticides in the air. The departures in the atmosphere are made from treatments (spray-drift); then by eolian erosion from treated grounds (contaminated dusts) and by more complex phenomena (transfers under gas phase and co-distillation). The development of mathematical models of transfers of pesticides since the treated surfaces passes by understanding the phenomena of transfers and the identification of the factors that control them. The nature of the ground, the climatic conditions during the application and the physico-chemical properties of compounds are so many factors, which influence mechanisms and importance of these departures towards the atmosphere. LERES (Laboratoire d'étude et de recherche en environnement et santé) developed a technique of trapping and analysis of some compound presents in the air. It is based on a trapping of compounds on a resin, then a thermal desorption before analyze by GC/MS. This technique, which allows to treat quickly a great number of samples, allowed us to determine a vertical gradient of concentrations of two herbicides, atrazine and alachlore, applied on maize, during 4 days following the treatment. Coupled with micrometeorological measures, these data allow to determine fluxes of transfers.