Studies on the behaviour of dihalogenated hydroxybenzonitriles in water

Abstract

The degradation behaviour of the pesticides bromofenoxim, bromoxynil, bromoxynil octanoate, ioxynil, chloroxynil and mecoprop has been studied in natural aerobic water. UV spectra of the herbicides dissolved in bidistilled or surface water have been recorded under different pH and irradiation conditions as a function of time. The compounds can be divided into two groups; the first group — bromoxynil, ioxynil, chloroxynil, mecoprop — is stable for several weeks, while the compounds of the second group — bromofenoxim and bromoxynil octanoate — start to decompose immediately. The rate of decomposition depends mainly on the irradiation or on the biological activity of the surface water. Therefore, much greater stabilities can be expected during underground passage. This instability must be considered during the determination of these herbicides.