| The purpose of this dissertation research was to test the utility of multimedia environmental fate models to evaluate the fate of pesticides in banana plantations. Chlorothalonil (CHT), a widely used fungicide was used as a tracer in this study. The research involves the modification and development of new methodologies to quantitate chlorothalonil and its main metabolites in water, soil, banana leaves, sediments and drift cards using gas and liquid chromatography coupled to mass selective detection. A field study was conducted to evaluate the rates of dissipation of CHT in soil and on banana leaves. Metabolite studies were conducted in the soil. Field dissipation half lives were 2.2 and 3.9 in soil and on the leaves, respectively. In water channels, CHT levels were as high as 286 ppb on the day of application and were as high as 50 ppb 24 hours post application. Drift cards were used to measure spray deposits on the soil and banana leaves as well as adjacent to water channels. An evaluative and local assessment of fate was conducted using the EQC and the SoilFug environmental fate computer models. The predicted concentrations in soil using the SoilFug model were in very good agreement with the measured concentrations. In channel water, model predictions were 2–7 times lower than the measured concentrations. It is concluded that a computer modeling approach can be an effective tool that will allow developing countries to predict the environmental fate of pesticides in tropical environment. |
