Biosensor monitoring of naphthenic acids remediation in mesocosms and constructed wetlands: a head-to-head comparison with orbitrap mass spectrometry.

Oil sands process-affected water (OSPW) contains complex mixtures of naphthenic acids (NA) that are the central targets for water treatment and reclamation. Here, we compared three whole-cell bacterial NA biosensors with Orbitrap mass spectrometry (MS) for quantifying NA remediation in greenhouse mesocosms and a pilot-scale constructed wetland. Solid-phase extracts from both systems were analyzed in parallel by Orbitrap MS and biosensor assays, enabling direct comparison of biosensor-derived NA estimates with MS-derived naphthenic acid fraction compounds (NAFC) concentrations. Across both treatment systems, biosensor outputs broadly tracked declines in NAFC measured by Orbitrap MS, and positive linear relationships were observed between methods. Biosensor 2 (3680-lux) and biosensor 3 (atuA-lux) showed, early rapid decreases in NA, whereas biosensor 1 (marR-lux) frequently remained elevated later in treatment. These differences are consistent with the distinct chemical response profiles of the biosensor panel and suggest that biosensor outputs reflect shifts in NA mixture composition as remediation proceeds. This interpretation is supported by the published Orbitrap analysis of the constructed wetland, which showed decreasing O2-NAFCs and increasing O3/O4-containing species, consistent with oxidative degradation. Together, these results support the use of NA-responsive biosensors as rapid and scalable complementary tools for tracking remediation trends, while Orbitrap MS remains the reference method for molecular-level characterization.