PM07 Pollutant Chemistry Transport, Cycling and Fate
Exhibit Hall
8:00 AM - Monday
(PM094) Measurement of pesticide fluxes from soils following pesticide application in the Northern Lake Victoria watershed.
Wejuli, M1, 2, Muir, D2, Kiremire, B1, Hecky, R3, 1 Makerere University, Kampala, Uganda2 National Water Research Institute, Burlington, Ontario, Canada3 University of Waterloo, Waterloo, Ontario, Canada
ABSTRACT- Pesticide use in the Eastern African region is on the increase, however, no study has addressed measurement of pesticide fluxes following application. Volatilization fluxes, from two soil types, a red soil (nitisol) and a black soil (gleysol) were determined for chlorpyrifos and malathion and their metabolites 3,5,6 trichloro-2-pyridinol (TCP), malathion di-carboxylic acid (MDCA) and malaoxon. Fluxes were determined using the chamber method. Highest flux intensities were observed within 66 hours following application. Cumulative losses at 143 hours in g/ha in the red soil were 9.382 chlorpyrifos, 0.316 TCP, 0.076 malathion, 0.076 MDCA, and 0.002 malaoxon. In the black soil, the cumulative losses in g/ha were 9.940 chlorpyrifos, 0.302 TCP, 0.047 malathion, 0.048 MDCA, and 0.003 malaoxon. Total cumulative losses at 143 hour for Chlorpyrifos (Chlorpyrifos + TCP) were 9.7 and 10.2 g/ha in the red and black soils respectively and for malathion (malathion + MDCA + Malaoxon) 0.154 and 0.088 g/ha in red and black soils respectively. These were 0.34% (red soil), 0.36% (black soil) of the application dose for chlorpyrifos, and 0.005% (red soil), 0.003% (black soil) of the application dose for malathion. Highest ambient air concentrations during sampling were observed within 66 hours and were 3.89, 0.85 and 0.24 micrograms/m3 for chlorpyrifos, TCP and malathion respectively. MDCA and malaoxon were not detected. Soil organic matter and clay content, soil moisture dynamics, sunshine hours, relative humidity and rainfall influenced levels of flux intensities, thus cumulative losses. However, there were no linear correlations as the influence of a combination of these factors varied from day to day. Fluxes were compared with fluxes of compounds measured in the United States and although the application doses were doubled, the fluxes in the watershed were found to be relatively low.
Key words: fluxes, pesticides, soil type, Africa