Tracing Contaminants: Assessing the Release of Trace Compounds via Managed Aquifer Recharge

Managed aquifer recharge (MAR) is a vital water management strategy that infiltrates surface water or wastewater effluent into aquifers through soil and sediment. However, this process can introduce pharmaceutically active compounds (PhACs) and their metabolites, posing environmental risks. This study investigates the transport behavior of four selected PhACs—caffeine, carbamazepine, diclofenac, and ibuprofen—under neutral pH conditions using column experiments in both unsaturated and saturated porous media. PhACs and a tracer solution were introduced into the system, and experimental results were simulated using the CXTFIT model to determine retardation and degradation factors. Experimental findings indicate high mobility for carbamazepine and ibuprofen across both unsaturated and saturated conditions. Ibuprofen behaved similarly to the tracer with a retardation factor of ~1 and negligible degradation, while carbamazepine showed slight retardation and tailing effects showing higher persistence in the water. Diclofenac significantly degrades in saturated media (44% recovery) but increases release under unsaturated conditions (98% recovery). This indicates the release of diclofenac through the vadose zone but can undergo degradation and retardation in aquifers. Caffeine displayed high retardation and degradation under both conditions independent of the moisture content during transport. These findings highlight the differential transport of PhACs during MAR showing contaminant release to the groundwater, emphasizing the need for effective management practices to mitigate contamination risks and ensure groundwater quality.