Degradation Kinetics and Metabolites of Carbamazepine in Soil

The antiepileptic drug carbamazepine (CBZ) is one of the most frequently detected human pharmaceuticals in wastewater effluents and biosolids. Soil is a primary environmental compartment receiving CBZ through wastewater irrigation and biosolid application. In this study, we explored the transformation of CBZ to biologically active intermediates in soil. Both 14C labeling and liquid chromatography–tandem mass spectrometry (LC–MS/MS) were used to track transformation kinetics and identify major degradation intermediates. Through 120 days of incubation under aerobic conditions, mineralization of CBZ did not exceed 2% of the spiked rate in different soils. Amendment of biosolids further suppressed mineralization. The fraction of non-extractable (i.e., bound) residue also remained negligible (<5%). On the other hand, CBZ was transformed to a range of degradation intermediates, including 10,11-dihydro-10-hydroxycarbamazepine, carbamazepine-10,11-epoxide, acridone-N-carbaldehyde, 4-aldehyde-9-acridone, and acrid...