Tracing persistent, mobile and toxic contaminants in the soil–plant–water system: A case study with Cichorium endivia

The reuse of reclaimed wastewater for agricultural irrigation is increasingly adopted as a sustainable response to freshwater scarcity driven by climate change. However, the fate of organic contaminants, particularly persistent, mobile, and toxic (PMT) substances, which are poorly removed by conventional wastewater treatment, remains a concern. In this study, Cichorium endivia (endive) was cultivated under greenhouse conditions and irrigated with water fortified with nine PMT compounds (benzophenone-3, clarithromycin, Dotarem, imazalil, metformin, sulpiride, terbutryn, tiapride and tramadol) at concentrations of 0.5, 5, 50, and 500 µg·L⁻¹. To evaluate their fate in the soil–plant–water system, samples of endive, soil, and drainage water were collected and analysed by mixed-mode liquid chromatography–tandem mass spectrometry, except for Dotarem, determined by LC coupled to inductively coupled plasma mass spectrometry. Results showed distinct partitioning: highly mobile compounds, such as metformin, reached concentrations of 88 ng·g −1 and 53 µg·L −1 in endive and drainage water, respectively, whereas moderately mobile ones, such as tramadol, primarily accumulated in soil (6423 ng·g −1 ). In contrast, low-mobility substances, such as benzophenone-3, showed minimal translocation (<10 ng·g −1 ). These findings reveal compound-specific behaviour of PMTs, emphasizing their differential accumulation and the need for risk-informed management of reclaimed wastewater in agriculture. At low PMTs concentrations, endive plants exhibited a hormetic response, with enhanced photosynthetic and transpiration activity indicating mild, non-damaging stress adaptation. Conversely, elevated PMT levels elicited pronounced physiological damage, characterized by significant growth inhibition, chlorosis, and widespread hormonal dysregulation, reflecting a shift toward defence activation and impaired growth performance.