Automation and evaluation of three pesticide fate models for a national analysis of leaching risk in Canada.

Under the National Agri-Environmental Health Analysis and Reporting Program (NAHARP), pesticide fate models are being used to develop an indicator of risk of water contamination by pesticides (IROWC-Pest) in Canada. The large number of model runs needed for a national analysis of the risk of pesticide leaching to ground water required the development of a computer program, AutoPFM (Automate Pesticide Fate Model), to automate the running of pesticide fate models. Using Manitoba as a test province, and the selected pesticide fate models PRZM, LEACHP, and MACRO, AutoPFM permitted the estimation of the leaching potential of the fourteen most used agricultural pesticides in Manitoba. Assuming an application rate of 300 g ha⁻¹ for each pesticide, only six pesticides demonstrated leaching across most soil series. For these six pesticides, there was significant correlation in how PRZM and LEACHP ranked the leaching potential of 337 Manitoba soil series. Because of its long run times, the estimation of leaching potential with MACRO was limited to two pesticides (2,4-D and MCPA). For these pesticides, MACRO showed significant correlation with the PRZM and LEACHP in ranking the soil series. Based on the results described in this paper, PRZM was chosen as the pesticide leaching model for use in IROWC-Pest.