Degradation studies of herbicides used in rice cultivation

Rice, like other important cereals, requires a great amount of chemicals, represented especially by fertilizers and pesticides. Nowadays, pesticides formulations are designed to offer a higher selectivity and a lower persistence in the environment than the formulations used in the past. But, unlikely, a lower persistence in the environment does not necessarily correspond to a lower toxicity. In fact, it has been demonstrated that many chemicals often undergo natural degradation reactions in the environment that may lead to the formation of new species potentially more toxic and stable than the precursors [1-3]. In the present study, Imazamox, Oxadiazon and Profoxydim that are the most important herbicides used in rice cultivation of Italy were undergone to degradation studies simulating natural environmental conditions. Aqueous solutions of the species both in mix and alone were exposed to sun light irradiation in a solarbox. Also hydrolysis processes were studied preserving the solutions at dark. At prefixed times, the solutions were analyzed by using a micro liquid chromatography system interfaced to a quadrupole-time of flight (QTOF) high resolution mass spectrometer. LC-MS analysis of the samples undergone to sunlight irradiation showed a decreased intensity of the herbicide signals, more evident than in the case of the hydrolysis processes. The kinetics of the degradation were evaluated and the degradation products were also investigated by LC-MS/MS analysis. This research has been supported by Fondazione Cariplo, grant n. 2014-1260.