Study of the Degradation of Haloxyfop-Methyl in Natural Waters in Senegal under the Effect of Solar Radiation and Evaluation of Its Herbicidal Activity

The objective of our study is to examine the impact of solar radiation on haloxyfop-methyl in an aqueous environment and to determine whether it is responsible for herbicidal activity. To do this, we first prepared a 10−4 M concentration solution of haloxyfop-methyl in distilled water, well water (at a height of 0.5 m), well water (at a height of 1 m), runoff water and river water, then exposed it to sunlight at regular intervals. This study shows that haloxyfop-methyl is highly unstable when exposed to sunlight. The percentages of photodegradation in these various types of water are 98%, 94.3%, 93%, 94.2% and 58.6% respectively. In all the environments studied, its photodegradation follows first-order kinetics and the half-lives found are relatively short, ranging from 9.18 to 47.47 minutes. A correlation was observed between the photodegradation rate of this herbicide and the amount of dissolved organic matter in these various environments. Indeed, the photodegradation of this herbicide was slower in environments where organic matter was more abundant. The study on herbicidal activity revealed that the initial product was primarily responsible for this activity, not its photoproduct. The latter showed slow degradation, even after 18 days of exposure to sunlight.