Assessing groundwater vulnerability in an arid region: investigating pharmaceutical contaminants in wastewater

Treated wastewater is increasingly utilized for irrigation and artificial groundwater recharge, particularly in dry regions such as the Middle East, where water scarcity demands sustainable resource management. However, reclaimed water may contain trace levels of pharmaceutical compounds, which can pose environmental and health concerns if not properly managed. These compounds could leach through the soil layers and contaminate groundwater, particularly when reclaimed water is used for irrigation and artificial recharge. Therefore, this study aimed to assess the potential for percolatoin through soil and leaching of eleven pharmaceutical compounds in four different soil types following the OECD 312 protocol. Solid phase and ultrasound-associated extractions were used to extract these compounds from 80 samples (16 leachate samples and 64 soil samples) which were subsequently analyzed using LC-MS/MS. The extraction results showed high recovery for most of the investigated compounds, reaching up to 109%, with an average recovery of 64%. The soil column results indicated that caffeine and cephalexin exhibited higher mobility, as they were detected in the leachates collected from the soil columns. In contrast, the other compounds showed strong sorption to soil particles, with notable accumulation in the top 5 cm of the soil profile. Caffeine and cephalexin penetrated up to 30 cm of the soil column and were detected at low concentrations (≤ 0.42% of their initial spiked concentration) in the leachate. These findings suggest that these caffeine and cephalexin may pose a potential risk of groundwater contamination due to their slight mobility in certain soil types. Overall, it can be concluded that most of the studied compounds exhibit limited leaching behavior across the four different studied soil types, indicating a negligible risk of potential pollution of groundwater from wastewater discharge or reuse.