Surface Water Monitoring Survey for Bensulfuron Methyl Applied in Paddy Fields

Abstract

Water samples from rice paddies, paddy drains, connecting streams, rivers and lakes have been analyzed for the rice herbicide bensulfuron methyl (BSM). BSM concentrations of river and lake water were in the range of <0.1-2.3 μg/l. Peak concentrations correlated with release of paddy water and diminished rapidly to non-detectable level within 1-2 months. BSM was not detected in any tap water samples taken during peak discharge periods. Samples from rice paddies had initial concentrations of 106 μg/l of BSM (at a maximum use rate of 75 g a.i./ha), dissipating with an average DT50 of about 2 days. Concentrations of BSM in water released from the paddies rapidly decreased as the drainage water moved downstream. These levels of BSM do not generally exceed EC50 for several aquatic organisms.