Effect of pH on dissipation kinetics of penoxsulam herbicide in waterPantnagar Journal of Research, Volume - 17, Issue - 3 ( September-December, 2019)
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Penoxsulam is a new herbicide of Triazolopyrimidine sulfonamide group. In order to explore its persistence in waters of varying pH, dissipation studies of penoxsulam herbicide were conducted in water maintained at three different pH (4, 7 and 9.2) at 1 and 2 µg ml-1 fortification levels. Water samples were collected at different time intervals i.e. 0 (2h), 1, 3, 7, 14, 30, 60, 90 days after herbicide application and processed for penoxsulam residues using HPLC. Degradation kinetics of penoxsulam was found to follow first order kinetics which could be better accounted by a monophasic pattern. The calculated half lives (t 1/2) in water samples of different pH depicted highest stability in acidic pH (t 1/2 = 69.0 to 77.0 days), followed by neutral (t 1/2 = 57.75 to 63.0 days) and alkaline pH (t 1/2 = 33.0 to 34.66 days) irrespective of the dose applied. Penoxsulam degrades rapidly in alkaline water and since it possesses low vapour pressure, its degradation in water is also dependant upon sunlight exposure which causes photolysis of the herbicide.
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