PROGRAMME

Due to water supply shortages that result from climate change, urbanization, regional droughts and pollution, treated wastewater (TWW) is commonly used to irrigate agricultural land in arid and semi-arid regions. Compared to aquatic systems, contaminants of emerging concern (CECs) only scarcely have been studied in the terrestrial environment. The likelihood of soil and groundwater contamination by CECs as a result of TWW reuse for irrigation depends on several factors such as the physicochemical properties of these contaminants, the type of wastewater treatment technology implemented, and climatic conditions (e.g., dilution of wastewater effluent, rainfall, temperature, and irradiance) (Kasprzyk-Hordern et al., 2009). Sorption is a crucial process that controls the mobility of CECs in soil. Soil properties such as pH, organic matter, and CECs play an important role in this process. Depending on the pKa of CECs and soil pH, CECs can emerge in nonionic, anionic, cationic or zwitterionic modalities. Herein, we investigated the occurrence and potential accumulation of 115 pharmaceuticals in soils collected, in July 2020, from treated wastewater (TWW)-irrigated fields with different irrigation histories (i.e., increasing irrigation periods from 0.5 to 10 years). More specifically, the TWW-irrigation has been implemented continuously in the 11 fields for 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 years, respectively. Moreover, 2 soil samples from adjacent neighboring rainfed fields, where wastewater irrigation was never applied before or tube-well water irrigation was applied, were collected and used as control samples providing reference “background” concentrations. Particle size analysis of sieved soils revealed that soil in the area showed characteristics consistent with a sandy clay loam, with sand and silt content ranging from 54 to 60% and 16 to 24%, respectively, while clay content varied from 21 to 26%. The sampled fields, located in the suburbs of Nicosia in Cyprus, were cultivated with alfalfa and irrigated with TWW from a membrane bioreactor treatment facility. A generic sample preparation method using solid-liquid extraction followed by solid-phase extraction was applied, which was adapted from Christou et al. (2017). The extracts were analyzed by ultra-high performance liquid chromatography coupled with a triple quadrupole mass spectrometer. Among the examined compounds, caffeine, carbamazepine, sulfapyridine, tramadol and clarithromycin were detected in all soil samples. Sarafloxacin, sulfadimidine, metoprolol and sulfamethoxazole had a frequency of appearance of more than 55%, while theophylline, lincomycin, cefalexin and amoxicillin had much lower frequency of appearance. These results indicate that attention should be paid to agricultural soils continuously irrigated with TWW not only from the point of view of TWW quality but also from the point of view of the concentration levels of CECs and their potential accumulation.