Lab-scale insights into the environmental fate of emerging contaminants from airport runoff

Contaminants of emerging concern (CECs) present in runoff pose risks to groundwater quality during their infiltration. Understanding the processes that control their attenuation is therefore essential for designing effective mitigation strategies. This research investigates the attenuation capacity of loess sediments overlaying a major Cretaceous chalky aquifer in Belgium, as part of a pre-feasibility study of soil aquifer treatment (SAT) system using airport runoff. In particular, the study aims to assess the natural ability of these sediments to filter and biologically degrade detected contaminants in airport runoff, thereby reducing their concentrations to levels compliant with water quality standards. Controlled batch experiments were thus conducted to analyze the sorption and biodegradability of key CECs, including PFAS, alkylphenols and benzotriazoles. The experiments were performed in triplicate using batch reactors filled with sediments and synthetic runoff. An abiotic control was included to distinguish between sorption and biodegradation. Results revealed distinct attenuation behaviours. Nonylphenol diethoxylate showed the highest removal, driven entirely by biodegradation with no contribution from sorption. Benzotriazole, tolyltriazole, PFOS, and 6:2 FTS showed moderate attenuation, primarily due to sorption for PFAS compounds. The remaining PFAS, - PFOA, PFHxA, and PFECHS - exhibited low attenuation, limited by sorption and no biodegradation. These findings confirm that loess sediments can reduce loads of certain CECs and also highlight the persistence of PFAS in water during infiltration. The results provide critical parameters for modeling CECs transport during SAT operations and support the safe management of airport runoff as a recharge source.