Assessment on attenuation, accumulation, and ecological risk of venlafaxine in aquatic ecosystems Co-exposed to...

The natural attenuation of venlafaxine (VEN) in aquatic ecosystems under environmentally realistic, multi-stressor conditions, including co-occurring polypropylene microplastics (PP MPs), remains insufficiently quantified. This study examined how biological communities and PP MPs influence VEN fate, dissipation kinetics, trophic transfer, and ecological risks using a 60-day trophically structured microcosm containing duckweed, mosquitofish, bitterling, river snails, sediment, and water. VEN (400 ng/mL) was applied under single and combined PP MP (500 items/L) exposures, and dynamics across compartments were quantified alongside ecological indicators, including plant growth, fish behavior, and snail reproduction. In abiotic controls, waterborne VEN declined to 29.0% (220.40 ± 4.43 ng/mL) by day 56, whereas biotic presence accelerated attenuation to 8.7% (35.00 ± 4.91 ng/mL), with further reduction to 7.1% (28.47 ± 1.09 ng/mL) under co-exposure. Sediment served as the primary sink, peaking at 55.20 ± 4.90, 42.56 ± 2.36, and 28.83 ± 1.31 mg/g in blank, VEN + Eco, and PP + VEN + Eco treatments. Duckweed exhibited continuous VEN bioaccumulation (up to 5.57-fold), while fish and snails displayed reverse U-shaped patterns; PP MPs reduced internal VEN residues by 1.3-2.1-fold. PP MPs mainly accumulated in sediment and snails (100-150 μm). Exposure affected duckweed growth and photosynthesis, induced behavioral changes in fish, and caused reproductive inhibition and oxidative stress in snails, although partial recovery occurred under co-exposure. Sediment microbial profiling identified Sphingomonas and RB41 as potential degraders of PP MPs and VEN. Toxicokinetic modeling indicated reduced VEN half-lives in VEN + Eco (12.36 d) and PP + VEN + Eco (10.41 d) relative to Eco alone (16.96 d), suggesting organism-mediated attenuation. Species sensitivity distribution and hazard quotient analyses indicated low ecological risk in biologically active systems. These results demonstrate that trophic interactions and microplastic presence influence VEN distribution and dissipation, highlighting the need to incorporate ecological complexity in pharmaceutical fate and risk assessments.