Enantioselective trophic transfer of chiral psychiatric pharmaceuticals in an effluent-impacted river food web

The enantiomeric signatures of chiral psychiatric pharmaceuticals (PPs) offer unique opportunities to trace their movement within food webs. However, the enantioselective trophic transfer of PPs in aquatic food webs remains poorly understood. Herein, the trophodynamics of 10 representative PPs, including 6 chiral pharmaceuticals and 4 achiral pharmaceuticals, were investigated in an effluent-impacted river food web in the Beiyun River, China. The median Σ₁₀PPs concentrations in aquatic organisms ranged from 11.6 ng/g dw (shrimp) to 352.7 ng/g dw (mussels). Diazepam (DIA) exhibited a biomagnification trend with a trophic magnification factor (TMF) of 1.28, whereas carbamazepine (CAR), sertraline (SER), citalopram (CIT), and fluoxetine (FLU) underwent trophic dilution, with TMFs ranging from 0.31 to 0.76. Enantiomeric fraction (EF) profiles across trophic levels (TLs) revealed significant enantioselective accumulation patterns for chiral PPs in aquatic species. The metabolic differences among aquatic organisms critically shaped the enantiomer signatures of chiral PPs in aquatic biota. The enantiomeric profiles of chiral PPs in lower-trophic-level biota were primarily governed by external exposure, whereas in vivo enantioselective metabolism became the predominant shaping factor in apex predators. This study highlights the role of species-specific metabolism in shaping the trophodynamics of chiral PPs in aquatic ecosystems, and underscores the necessity of incorporating enantiomeric perspective into environmental risk assessment for chiral compounds.