The objectives of this study were to develop a one dimensional (vertical), time variable mathematical model for the transport and reactions of pesticides and nitrates though the unsaturated zone to surficial aquifers. Testing and validation of the model with data from laboratory and field studies on alachlor, atrazine, and nitrates was conducted. The model can provide better understanding of processes effecting pesticides and nitrates in the subsurface environment. Additionally, the model can provide predictions of pesticide and nitrate concentrations under varied application rates, soil types, climatic conditions, electron acceptor conditions, etc. Two field sites were utilized-Amana, Iowa, and Tipton, Georgia. The model performed well and enabled investigators to acquire additional funding through the EPA Hazardous Substances Research Center for Region 7 and 8 for further research.