Evaluation of the software package 'EXPRES' to study the fate and transport of pesticides in the unsaturated zone

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University of New Brunswick
The primary processes associated with pesticide transport and attenuation are flow in the unsaturated zone, partitioning and transformation of the pesticide, and plant uptake. A software package (EXPRES) is used to apply the computer model LEACHM to simulate these processes. The 'EXPRES' software includes environmental data for various Canadian locations as well as technical data for commonly applied pesticides. These data are used to perform sensitivity analyses with the pesticide Atrazine on a cornfield in Harrow, Ontario. In the sensitivity analyses, the effects of changes in precipitation, fractional organic carbon content and date of pesticide application, are investigated. The primary outputs for the EXPRES model were concentration-depth profiles of Atrazine on a given date and flux of Atrazine at a given depth in time. Based on the realistic input data, it was found that a 20 percent change in precipitation amount is more significant then a 50 percent change in fraction of organic carbon. The date of application within two weeks of the normal date had little effect the fate and transport of Atrazine for a specific year. Finally, the potential for contamination of groundwater by Atrazine and the usefulness of EXPRES are discussed.