Abstract
The use of wastewater in agricultural sector for irrigation and fertilization purposes is not a recent practice. However, until the past couple decades this practice has been of increasing interest regarding the global safety, particularly human health. Besides to the useful nutrients and organic matter that wastewater introduces to the agricultural lands, pharmaceutical active compounds (PhACs) and other organic micropollutants are also co-introduced leading to the presence of undesired chemicals in agroecosystems, most remarkably in crops intended for human consumption. Incredible effort has been made in last couple decades to analyze such contaminants in environmental samples, yet there is still a lack of robust analytical methods for the extraction and quantification of a large number of PhACs and other wastewater pollutants, and a lack of knowledge regarding their fate and behavior in the entire agroecosystem including soil and crops.In this context, the first objective of this thesis was to develop robust and sensitive analytical methodologies specific to soil and crops matrices (e.g., root and leave) to analyze a large number of wastewater organic contaminants mainly PhACs and their metabolites. QuEChERS-based methods followed by detection and quantification on high-resolution mass spectrometry were successfully developed for soil, lettuce/leek root and lettuce/leek leaves. Good recoveries were obtained for the 48 studied compounds in all matrices (in general between 80 and 120 % for most of the compounds). Detection and quantification of compounds was performed on a high-resolution mass spectrometry on quadrupole-time of flight (Q-TOF) coupled to liquid chromatography provided from SCIEX technology. Comparing the two recently developed acquisition modes high-resolution multiple reaction monitoring (MRMHR) and Sequential Window Acquisition of All Theoretical Fragment-Ion Spectra (SWATH) gave similar results, though MRMHR gave more consistent results for most of the compounds. Finally, satisfying detection and quantification limits were obtained for all 3 matrices, for instance lettuce leaves matrix in MRMHR acquisition gave detection limits ranging from 0.01 to 0.12 ng/g and quantification limits ranging from 0.04 to 0.38 ng/g dry weight (d.w).Later, the following objective was to apply these methodologies on real agricultural field irrigated with local treated domestic wastewater. The second objective allowed us to understand the distribution of selected contaminants in soil and crops and calculate their bioconcentration factors, to discriminate their degradation in soil and crops, and finally to assess the potential risk for human consumption of wastewater irrigated crops. Two years of successive growth cycles of lettuce and leek under greenhouse field conditions were successfully implemented. Different kinds of water were used for irrigation mainly domestic treated wastewater, following real drip irrigation conditions. Little accumulation in soil and crops was found, which was explained by the intensive degradation of contaminants in soil and metabolism in crops. A few metabolites were detected in lettuce leaves, particularly carbamazepine-epoxide which was produced by the lettuce metabolism. Finally, this study revealed a de minimis human health risk related to the consumption of raw vegetable irrigated with treated wastewater.The last objective was to study the fate of selected contaminants introduced in soil by wastewater irrigation, when they are exposed to the ubiquitous filamentous soil fungi Trichoderma. Implemented experiments in liquid medium revealed for the first time an important ability of Trichoderma species, namely T. harzanium and T. asperellum to degrade two fluoroquinolones antibiotics (ciprofloxacin and ofloxacin), and one fungicide (climbazole). Equally important, new metabolites of ofloxacin and climbazole were tentatively identified in this study for the first time.