Contaminants of emerging concern (CECs) in olive plant irrigated with wastewater: uptake and distribution into plant tissues

The ever-increasing demand for water and the limited availability of freshwater exacerbated by ongoing climate change, especially in arid and semi-arid climates, bring attention back to the potential use of wastewater. The use of reclaimed wastewater for irrigation purposes is a globally adopted and increasingly common agricultural practice, providing an alternative water source for the agricultural sector. Wastewater reuse could have potential environmental and health risks associated with the presence of contaminants of emerging concern (CECs), including pharmaceuticals and personal care products, which are introduced into the agroecosystem through irrigation. CECs, once in the soil, can be taken up by the roots and translocated into several plant tissues, entering the food chain and becoming a major global food safety issue. The present study aimed to evaluate CECs uptake and accumulation dynamics in potted olive trees (Olea europaea L.) irrigated with treated municipal wastewater. Plants were exposed to 10 CECs, belonging to the main classes of contaminants such as anti-epileptics, antibiotics and anti-inflammatories. Plants were irrigated with fresh water (Control) and with treated municipal wastewater spiked with selected CECs at a concentration of 200 μg/L (1X) and 600 μg/L (3X) during the 2021 irrigation season. Extraction of CECs from soil and plant organs was performed with the QuEChERS method and CECs concentrations accumulated in the samples were determined by the high resolution mass spectrometry coupled with liquid chromatography (LC-HRMS/MS). Results showed that the highest frequency of CECs detection was observed in soil and root samples, maintaining the accumulation in other plant organs below the limit of quantitation (LOQ) due to several fate-determining processes or degradation pathways. Only two compounds (i.e., carbamazepine and fluconazole) were detected at significantly higher concentrations in plant tissues, accumulating mainly in the leaves, where CECs concentration was higher than that in the roots. These preliminary results reveal that some CECs can be taken up by plants and accumulated in several plant organs when introduced in the agroecosystem through irrigation with treated wastewater. The fate of CECs in the soil-plant system is a future research topic to be investigated in order to choose and adopt wastewater irrigation management strategies aimed at limiting CECs accumulation in plant tissues, to achieve safe food productions and environmental health.