Target and Not- target approach for the identification of pesticides and emerging contaminants in paddy water

Rice crop requires a great amount of chemicals like fertilizers and pesticides. Nowadays, pesticides formulations are designed to offer both high selectivity and low persistence in the environment and they can undergo degradation by the effect of the environmental conditions as water, sunlight and bacteria. According to previous studies, pesticides can potentially transform into new emerging contaminants, more toxic than the precursors, by the effect of sunlight or other environmental factors. In this study, paddy water samples collected a rice farm located in the main Italian rice basin (northwestern zone of the Padana Plain) in the North-Western zone of Italy were analyzed by the use of a micro LC system interfaced with a quadrupole-time of flight (QTOF) high resolution mass spectrometer. The quality of water was therefore evaluated according to two approaches: target and non-target. Using the target approach, the most used pesticides in rice cultivation (like Imazamox, Oxadiazon, Pendimethalin, Profoxydim and Tryciclazol) were identified and quantified. Regarding the non-target approach, since the well-known difficulties associated to structure elucidation and the limited availability of mass spectral libraries for LC-HiresMS, all the mass and mass/mass spectra were recorded using the SWATHTM (Sequential Window Acquisition of all THeoretical Mass Spectra) acquisition method. In this way, the presence of new emerging contaminants, originated from the degradation of the pesticides was investigated and their probable chemical structures were elucidated.